Synthesis and properties of Sr2La2NiW2O12, a new S = 1 triangular lattice magnet

Smerechuk, A.; Guilherme Buzanich, A.; Büchner, B.; Wurmehl, S.; Morrow, R.

doi:10.1107/S2052520624007091

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STRUCTURAL SCIENCE
CRYSTAL ENGINEERING
MATERIALS

ISSN: 2052-5206

Volume 80| Part 5| October 2024| Pages 467-473

https://doi.org/10.1107/S2052520624007091

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Synthesis and properties of Sr₂La₂NiW₂O₁₂, a new S = 1 triangular lattice magnet

Anastasiia Smerechuk,^a Ana Guilherme Buzanich,^b Bernd Büchner,^a Sabine Wurmehl ^a and Ryan Morrow ^a ^*

^aLeibniz Institute for Solid State and Materials Research IFW Dresden, Helmholtzstraße 20, Dresden, 01069, Germany, and ^bFederal Institute for Materials Research and Testing (BAM), Richard-Willstaetter-Str. 11, Berlin, 12489, Germany
^*Correspondence e-mail: [email protected]

Edited by L. Dawe, Wilfrid Laurier University, Waterloo, Ontario, Canada (Received 29 March 2024; accepted 18 July 2024; online 30 August 2024)

This article is part of a collection of articles from the IUCr 2023 Congress in Melbourne, Australia, and commemorates the 75th anniversary of the IUCr.

Magnetic materials featuring triangular arrangements of spins are frequently investigated as platforms hosting magnetic frustration. Hexagonal perovskites with ordered vacancies serve as excellent candidates for two-dimensional triangular magnetism due to the considerable separation of the magnetic planes. In this work, the effects of chemical pressure on the ferromagnetic ground state of Ba₂La₂NiW₂O₁₂ by substitution of Ba²⁺ with Sr²⁺ to produce Sr₂La₂NiW₂O₁₂ are investigated. The two materials are characterized using synchrotron-based XRD, XANES and EXAFS in addition to magnetometry in order to correlate their crystal structures and magnetic properties. Both materials form in space group R3, yet as a result of the enhanced bending of key bond angles due to the effects of chemical pressure, the T_C value of the magnetic Ni²⁺ sublattice is reduced from ∼6 K in Ba₂La₂NiW₂O₁₂ to 4 K in Sr₂La₂NiW₂O₁₂.

Keywords: frustrated magnetism; complex oxides; perovskite; X-ray diffraction; triangular magnet.

1. Introduction

Frustrated magnetism, typically defined empirically as the case where a large ratio exists between the Weiss temperature and the onset temperature of long-range magnetic order, has been suggested to arise from a variety of fundamental origins. However, for the realization of a maximally frustrated magnetic system as it is manifested in various theoretically proposed spin liquids (Balents, 2010 ; Savary & Balents, 2017 ), one nearly universal ingredient is the implementation of geometric spatial arrangement of the spins in the solid which yields a fine balancing of the exchange interaction(s) between them. As highly degenerate energy levels of the ground state are typically associated with such an entanglement, even small perturbations of the crystal structure can result in preferential solutions to alleviate the frustration. As theoretical models can avoid this contingency, many of the theoretical constructs involve simple idyllic patterns as templates for calculations such as the famous kagome or honeycomb lattices.

One of the simplest of such frustrated arrangements, frequently used as an example for introductory purposes, is the antiferromagnetic (AFM) interaction on a triangle, and by extension, tilings in two and three dimensions which are based on triangular arrangements, such as the edge-sharing tetrahedra found in the f.c.c. lattice. While the kagome lattice, also based on triangles, has maintained its status as a frustrated system, the completely tiled 2D triangular plane has received less attention due to the solution to the system which commonly materializes – the 120° AFM structure. However, recent works in the frustrated cobaltate magnet systems suggest the possibility of Kitaev interactions between high-spin d⁷ Co²⁺ at low temperatures which may yet again produce interesting results even in 3d transition metal triangular magnets (Liu & Khaliullin, 2018 ; Kim et al., 2021 , 2023 ).

While triangular patterns are very commonly observed in a wide variety of crystalline lattices, simple chemical formulae such as binaries frequently bring neighboring magnetic planes in close proximity, allowing for the out-of-plane terms to significantly impact the properties. Complex oxides, on the other hand, enable for rather exotic and elaborate crystal structures to be designed resulting in well separated 2D planes and more idealistic correspondence to theoretical models. Hexagonal perovskites, one such class of materials, have been studied for many reasons, but recent interest has shown these materials to include excellent candidates for low-dimensional triangular magnets and quantum materials (Nguyen & Cava, 2021 ).

One such variant of hexagonal perovskite, first demonstrated in the 1960s (Longo et al., 1965 ), has a generalized quadruple perovskite formula (A₄B₄O₁₂) convoluted by both cation and vacancy ordering to yield a formula of A₄BB′₂O₁₂. The crystal chemistry of these vacancy and cation ordered hexagonal perovskites was elaborated considerably in the 1980s in the group of Kemmler-Sack (Herrmann & Kemmler-Sack, 1980a ; Rother & Kemmler-Sack, 1980 ; Herrmann & Kemmler-Sack, 1981 ; Herrmann & Kemmler-Sack, 1980b ; Kemmler-Sack & Herrmann, 1980 ), demonstrating some of the chemical flexibility enjoyed by its more commonly known simple perovskite parents. Apparently abandoned for several decades, these materials have recently resurfaced in the context of a materials platform to study low-dimensional and frustrated magnetism (Evans et al., 2021 ).

While many potential members remain yet unexplored, several teams have published results which begin to paint a picture of the interesting accessible properties in these systems. Recent research has focused on inclusion of a single magnetic ion at the B site with an oxidation state of 2+, with focus on the magnetism of triangular lattices of Mn²⁺, Co²⁺ and Ni²⁺ (Doi et al., 2017 ; Rawl, Lee et al., 2017 ; Kojima et al., 2018 ; Saito et al., 2019 ). Meanwhile, the counterbalancing A and B′ cations typically are all nonmagnetic to yield a clean 2D magnetic system. The A cations utilized thus far have been a combination of alkaline earth and rare earth cations typical of hexagonal perovskites, while the B′ cations include d⁰ configuration ions such as Re⁷⁺, W⁶⁺, Te⁶⁺ and Nb⁵⁺. The combinations of charge balance between the A and B′ sublattices allow for numerous combinations of nonmagnetic scaffolding for each magnetic lattice, in turn allowing for studies with the application of chemical pressure by aliovalent or isovalent cation substitutions (Rawl, Lee et al., 2017 ). Furthermore, materials with yet another doubling of the formula and greater dilution of the magnetic layers in these materials produce even greater separation between the layers in related A₈BB′₆O₂₄ compounds (Rawl, Ge et al., 2017, 2019 ).

In this work, the topic of investigation concerns the magnetism of Ni²⁺ in A₄BB′₂O₁₂ materials. Two such compounds have been reported thus far with considerable difference in properties. Ba₂La₂NiTe₂O₁₂ features AFM interactions on the triangular lattice, with two magnetic transitions upon cooling: from paramagnetic to a collinear AFM structure and then to a 120° structure (Saito et al., 2019). Conversely, Ba₂La₂NiW₂O₁₂ exhibits ferromagnetic (FM) interactions and a low-temperature long-range-ordering transition to an FM state (Rawl, Lee et al., 2017). In order to shed further light on the surprising system, in this work we synthesize additional member Sr₂La₂NiW₂O₁₂, effectively applying chemical pressure to Ba₂La₂NiW₂O₁₂. Both of these materials are characterized for their magnetic properties and crystal structures using synchrotron X-rays for direct comparison, both to each other as well as to recent neutron powder diffraction results (Yu et al., 2023 ).

2. Experimental

Polycrystalline samples of Sr₂La₂NiW₂O₁₂ and Ba₂La₂NiW₂O₁₂ were synthesized in high-density alumina crucibles using the solid-state method. Stoichiometric quantities of La₂O₃, SrCO₃ or BaCO₃, NiO and WO₃ were weighed, thoroughly ground in an agate mortar and pestle, and heated in a muffle furnace at 1250°C for a period of 24 h. The rate of heating to the dwell temperature was 100°C h⁻¹, while the rate of cooling after dwelling was 50°C h⁻¹. Prior to weighing, the La₂O₃ reagent had been dried overnight in a muffle furnace at 800°C.

For the preliminary characterization by in-house powder X-ray diffraction (XRD), the samples were finely ground and mounted on to a thin-film sample holder, to be analyzed on a Stoe Stadi diffractometer, in transmission geometry with Co Kα₁ radiation, equipped with a Ge monochromator and a DECTRIS MYTHEN 1K detector. Powder XRD data were collected at room temperature (∼293 K) on beamline P02.1 (PETRA III) with an energy of approximately 60 keV and λ = 0.2073 Å (Dippel et al., 2015 ). Data were acquired on a Perkin Elmer XRD1621 CN3-EHS (200 µm × 200 µm pixel size, 2048 × 2048 pixel area) area detector and integrated using the Fit2D program (Hammersley et al., 1996 ). Powder XRD data were analyzed with the Rietveld method using the GSAS EXPGUI program (Larson & Von Dreele, 2004 ; Toby, 2001 ).

X-ray absorption spectroscopy (XAS) measurements containing both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) were performed in fluorescence mode at the Ni K-edge (8.333 keV) at the BAMline (Buzanich et al., 2023 ), located at BESSY II (Berlin, Germany). The incident energy was tuned by a double-crystal monochromator in a Si(111) arrangement (ΔE/E = 2 × 10⁻⁴). A 5 cm-long ionization chamber filled with nitrogen was used to measure the I₀ signal (before the sample). The beam size was 4 mm (horizontal) × 1 mm (vertical). A four-element silicon drift detector was used to collect the fluorescence signal in backscattered mode, as described by Buzanich et al. (2023). The measurement protocol was: 10 eV steps until 20 eV before the edge, followed by 0.25 eV steps until 20 eV above the edge and 2 eV steps until 200 eV above the edge. From then on equidistant k-steps were taken (every 0.06 Å) until 16 Å. The data evaluation and treatment were performed by using the ATHENA program from the DEMETER (Ravel & Newville, 2005 ) package. The EXAFS signal was Fourier transformed, by convoluting a Hanning-type window with the signal in k-space between 2 and 14 Å⁻¹, with tapering parameter dk = 2.

The temperature and field dependence of the direct current magnetization of both samples were measured using a Quantum Design SQUID MPMS. The powder samples were contained in size #4 gel capsules, mounted inside straws, and attached to a standard sample stick for insertion into the device. Temperature dependence of the magnetization was collected in an applied magnetic field of 1000 Oe following both field cooled (FC) and zero field cooled (ZFC) protocols in the temperature range of 2 to 350 K. Field dependent measurements were collected at 2 K, starting from a virginal ZFC state, in the applied field range of ±50 kOe. No corrections to the data for the diamagnetism of the sample holder were necessary given the magnitude of the response.

3. Results and discussion

Both samples crystallize in rhombohedral space group $[R{\bar 3}]$ with an overall crystal structure similar to a quadrupled hexagonal perovskite (Nguyen & Cava, 2021). The primary difference is that the trimer of face-sharing octahedra normally found in such a hexagonal perovskite instead contains an ordered vacancy in the center of this trimer. The location of these sites is highlighted in Fig. 1. The severed trimers are linked by corner-sharing connections to NiO₆ octahedra. Much like the more typical hexagonal perovskites, both the face-sharing columns and the linking octahedra are arranged in a triangular layout when viewed down the c axis, which has lent hexagonal perovskites opportunities to serve as platforms for low-dimensional and frustrated magnetism. The distance separating the nearest-neighbor Ni ions is equivalent to the a unit-cell parameter in each material. However, notably, there is no direct connection via shared ligands between neighboring NiO₆ octahedra. Therefore, while the severed connectivity between the triangular planes weakens potential out-of-plane exchange interactions, the exchange mechanisms within the plane are also longer ranged and, therefore, of marginal strength. The consideration of a direct exchange between the nickel ions as a potential mechanism is supplemented by superexchange pathways which take into account the neighboring chemical scaffolding. The bonding angle considering a pathway from Ni through W to the nearest Ni is just shy of 90°, meanwhile, there exists the possibility for exchange to proceed via a Ni–O–O–Ni pathway. Interestingly, it appears that the comparison of Ba₂La₂NiW₂O₁₂ and nearly isostructural Ba₂La₂NiTe₂O₁₂ directly probes these pathways. While Te⁶⁺ has a full d shell, participation in superexchange is precluded, and the remaining mechanism of Ni–O–O–Ni lends an AFM exchange and resultant properties. Meanwhile, Ba₂La₂NiW₂O₁₂ has an empty d shell in the chemical scaffolding in W⁶⁺. Apparently, the availability of these orbitals for participation in a super-superexchange mechanism is sufficient to overtake the AFM Ni–O–O–Ni mechanism, which likely persists. The nearly 90° exchange pathway through W yields an FM exchange, much like what is seen in the Goodenough–Kanamori rules (Goodenough, 1955 ; Kanamori, 1959 ) of simpler directly linked polyhedra. Interestingly, it is highly rational that both mechanisms should be sensitive to any distortions or rotations of the octahedra and resulting oxygen position.

Figure 1
Representation of the crystal structure of Sr₂La₂NiW₂O₁₂ viewed along the a axis, highlighting the ordered cation vacancies (left), and a cross sectional perovskite-like slab viewed along the c axis showing the triangular arrangement of magnetic Ni ions (bottom right). This figure was drawn using the VESTA (Momma & Izumi, 2011

) software package.

The refinement of the crystal structure models against synchrotron powder XRD data are shown visually in Fig. 2 and numerically in Table 1. Two structural models have been proposed in the literature for similar materials with space groups $[R{\bar 3}]$ and $[R{\bar 3}m]$ (Saito et al., 2019), including a recent comparison and assignment of $[R{\bar 3}]$ for Sr₂La₂NiW₂O₁₂ and Ba₂La₂NiW₂O₁₂ on the basis of neutron diffraction (Yu et al., 2023). The primary difference between the two structural models is that the $[R{\bar 3}]$ model includes an out-of-phase rotation between neighboring corner-connected octahedra within the perovskite-like slabs as can be seen in Fig. 1, whereas the $[R{\bar 3}m]$ model does not (see supporting information, Fig. S1). While neutron diffraction is more sensitive to the differences in these structural models as they primarily involve oxygen positions, there is a statistically significant difference in the fitting of the synchrotron XRD patterns favoring the octahedral tilt model associated with $[R{\bar 3}]$ , which is consistent with the previous report (Yu et al., 2023). The refined parameters of both structural models for both materials are given in Table 1 for direct comparison.

Table 1
Crystallographic data from synchrotron XRD for Ba₂La₂NiW₂O₁₂ and Sr₂La₂NiW₂O₁₂ in both space groups considered in the text

In both space groups, coordinates Ba/Sr x, Ba/Sr y, La x, La y, Ni x, Ni y, Ni z, W x and W y are equal to 0.

	Ba₂La₂NiW₂O₁₂	Ba₂La₂NiW₂O₁₂	Sr₂La₂NiW₂O₁₂	Sr₂La₂NiW₂O₁₂
Space group	$[R{\bar 3}]$	$[R{\bar 3}m]$	$[R{\bar 3}]$	$[R{\bar 3}m]$
a (Å)	5.66176 (8)	5.66167 (8)	5.59271 (8)	5.59271 (8)
c (Å)	27.3620 (6)	27.3623 (6)	26.5639 (6)	26.5638 (6)
V (Å³)	759.59 (3)	759.58 (3)	719.56 (3)	719.56 (3)
R_wp (%)	7.54	7.81	7.91	8.06
χ²	158.9	170.2	147.1	152.2
Ba/Sr z	0.13276 (13)	0.13285 (15)	0.13430 (16)	0.13433 (16)
La z	0.29296 (17)	0.29276 (17)	0.29173 (13)	0.29158 (13)
W z	0.41860 (14)	0.41848 (14)	0.42188 (10)	0.42176 (10)
O1 x	0.483 (6)	0.4951 (14)	0.460 (9)	0.4966 (15)
O1 y	0.498 (6)	0.5049 (14)	0.467 (9)	0.5034 (15)
O1 z	0.1175 (4)	0.1174 (4)	0.1238 (4)	0.1232 (4)
O2 x	0.432 (3)	0.4841 (12)	0.422 (3)	0.4811 (15)
O2 y	0.462 (3)	0.5160 (12)	0.462 (3)	0.5189 (15)
O2 z	0.2944 (5)	0.2947 (5)	0.2910 (5)	0.2914 (4)
∠Ni—O2—W (°)	160.6 (8)	169.8 (7)	159.4 (8)	171.0 (8)
∠Ni—W—Ni (°)	89.65 (6)	89.70 (7)	88.85 (5)	88.91 (6)
∠Ni—O2—O2 (°)	122.9 (8)	122.9 (8)	147.9 (5)	137.4 (5)
Ni—O2 (Å)	2.10 (3)	2.10 (3)	2.15 (3)	2.11 (3)
W—O1 (Å)	1.79 (5)	1.815 (11)	1.85 (6)	1.83 (6)
W—O2 (Å)	1.98 (2)	1.950 (12)	1.91 (2)	1.89 (3)

Figure 2
Synchrotron XRD patterns collected at room temperature (∼293 K) of (a) Ba₂La₂NiW₂O₁₂ and (b) Sr₂La₂NiW₂O₁₂. The black symbols, red curve and blue curve correspond to the observed data, calculated pattern and difference curve, respectively. Black vertical bars (top) refer to Bragg angles of the main phase while the secondary ones below refer to (a) BaWO₄ and La₂O₃ and (b) SrWO₄.

The structural impact of the cation substitution can be clearly seen by comparing the structural models of the two materials. The substitution of smaller Sr²⁺ for Ba²⁺ creates chemical pressure by compressing the material to alleviate potential underbonding of the relatively smaller cation. This can be seen in the unit-cell parameters and unit-cell volume, which are noticeably reduced. Important effects of this compression include the reduced distance between neighboring Ni²⁺ ions and the change in bonding angles implicated in the superexchange mechanisms previously described. In order to verify the accuracy of the bond lengths and angles of importance, it is instructive to compare directly to the neutron diffraction results which can be presumed to more accurately determine the oxygen positions. In Ba₂La₂NiW₂O₁₂ and Sr₂La₂NiW₂O₁₂, respectively, the Ni—O2 bond lengths are given as 2.064 (4) Å and 2.051 (2) Å, the W—O2 bond lengths as 2.009 (6) Å and 2.004 (2) Å, and ∠Ni—O2—O2 bond angles as 121.50 (5)° and 120.62 (4)° (Yu et al., 2023). While these values are qualitatively similar to those refined and presented in Table 1 in the present work, the refinement based on synchrotron X-ray data places the O2 anions closer to W. Presuming a higher precision of the oxygen position refined from neutron data, this results in a slight distortion of the octahedra and bond angles. Meanwhile, the a unit-cell parameters of 5.66126 (9) Å and 5.59654 (5) Å and c unit-cell parameters of 27.35363 (3) Å and 26.58389 (1) Å given for Ba₂La₂NiW₂O₁₂ and Sr₂La₂NiW₂O₁₂, respectively (Yu et al., 2023), compare very closely to the refined values given in Table 1.

Several impurities exist in the samples which could be accounted for in the refinement process. The Sr₂La₂NiW₂O₁₂ sample contains 4.24 (9)% of SrWO₄ by weight fraction, while the Ba₂La₂NiW₂O₁₂ sample contains 5.99 (11)% BaWO₄ and 0.42 (3)% La₂O₃. As the impurities determined were nonmagnetic, they were not considered detrimental to subsequent magnetic characterizations after attempts to purify the samples by revised synthesis were not entirely successful.

The assumption that the magnetic Ni ions were in the 2+ oxidation state was tested by XAS measurements using hard X-rays near the Ni K-edge (8.333 keV) as shown in Fig. 3. Standards used in the measurement for comparison purposes were a Ni metal foil and NiO. As shown in the inset of Fig. 3(a), the position of the edge for both samples is directly beneath the signal from the Ni²⁺ standard, signifying a strong agreement with the assumption of the nominal oxidation state. Furthermore, the EXAFS components of the data were able to be analyzed to produce pair correlations corresponding to the local structure radiating from Ni centers. From the basis of the refined averaged crystal structure, tentative assignments of the pair distances to neighboring species could be made. The similarity of the crystal structures is immediately evident in the distribution of the peaks of the two samples. The relatively small change in unit-cell parameters makes little impact on the curves, yet in this data, there is the possibility of checking for cation disorder, namely, that the smaller Sr²⁺ may yield antisite disorder with La³⁺ whereas Ba²⁺ does not seem to. We can observe a similar radial distribution of the peaks between both samples, even at higher radial distances. Noteworthy are the peaks at ∼3.8 Å and ∼5.8 Å, which can arise from Ni–Sr and Ni–Ba scattering paths, respectively. The magnitude in the Ni–Ba case is higher than Ni–Sr, due to stronger scattering from Ba than from Sr. In addition, if there is a distortion prone to happen in the case of Sr, this would produce a lower magnitude in the scattering paths at those distances.

Figure 3
(a) Normalized XAS data measured at room temperature near the Ni K-edges of Ba₂La₂NiW₂O₁₂, Sr₂La₂NiW₂O₁₂, standard Ni⁰ foil, and standard Ni²⁺O. The inset displays a close up of the edge position. (b) The Fourier transformed EXAFS component, with peaks corresponding to distances from Ni to neighboring pairs, are labeled in the figure.

Having established these details, we now turn to examine the magnetic behavior of the samples. Both samples have an apparently FM ground state as witnessed in their low-temperature hysteretic field dependence, as shown in Figs. 4(a) and 4(b). Considering the given Ni²⁺ oxidation state, the preponderance of Ni²⁺O₆ octahedra in the literature establish a high-spin d⁸ S = 1 electronic configuration as the most reasonable expectation. Indeed, the saturation magnetization of both compounds is very nearly the ideal 2 μ_B per Ni²⁺ with 1.87 μ_B and 1.93 μ_B in Ba₂La₂NiW₂O₁₂ and Sr₂La₂NiW₂O₁₂, respectively. In light of the presence of approximately 6% and 4% of nonmagnetic impurities in the two samples, a correction accounting for the precise moles of magnetic species would bring these two numbers even closer together and even closer to the nominal value of 2 μ_B. Given the proximity of these values to the nominal value, interpretations of the ground state as anything more complex than a trivial collinear ferromagnet can be considered unreasonable. Both materials are soft ferromagnets, with low coercive fields, and with Sr₂La₂NiW₂O₁₂ being softer than Ba₂La₂NiW₂O₁₂.

Figure 4
The field dependence of the magnetization of (a) Ba₂La₂NiW₂O₁₂ and (b) Sr₂La₂NiW₂O₁₂ at 2 K, the temperature dependence of the magnetization of (c) Ba₂La₂NiW₂O₁₂ and (d) Sr₂La₂NiW₂O₁₂ with FC conditions (red) and ZFC conditions (blue) plotted against the left axis and with the inverse of the FC dataset (black) plotted against the right axis with a fitting described in the main text, and (e) displays the comparison of the low-temperature FC data of both compounds with the derivative of both plotted in the inset.

The temperature dependence of the magnetization reveals FM transitions in both materials at low temperatures. The temperatures of these transitions can be best assigned on the basis of the derivative of the magnetic susceptibility with respect to temperature, as shown in the inset of Fig. 4(e). T_C lies just above 6 K and 4 K in Ba₂La₂NiW₂O₁₂ and Sr₂La₂NiW₂O₁₂, respectively, within resolution of the temperature spacings measured. These values agree are consistent with those previously reported (Yu et al., 2023) on the basis of several methods. The higher temperature portion of both data sets adheres to a well behaved Curie–Weiss law, as shown in Figs. 4(c) and 4(d). The effective moments of both samples are similar with 3.08 μ_B and 3.00 μ_B for Ba₂La₂NiW₂O₁₂ and Sr₂La₂NiW₂O₁₂, respectively. These values can be compared to a spin only effective moment of 2.83 μ_B, with a positive orbital contribution typical of a d⁸ configuration. The Weiss temperatures were +5.83 K and +5.40 K for Ba₂La₂NiW₂O₁₂ and Sr₂La₂NiW₂O₁₂, respectively, highlighting the presence of FM interactions. The corresponding literature values reported for Ba₂La₂NiW₂O₁₂ by Rawl, Lee et al. (2017) were 3.19 μ_B for the effective moment, +25.5 K for the Weiss temperature, and with a T_C value of 6.2 K while those reported by Yu et al. (2017) for Ba₂La₂NiW₂O₁₂ and Sr₂La₂NiW₂O₁₂, respectively, are effective moments of 3.17 μ_B and 3.13 μ_B, Weiss temperatures of 7.4 K and 8.4 K, and T_C values of 4.3 and 4.8 K.

The results, combined, indicate that the substitution of Sr for Ba effectively applies chemical pressure to the system, reducing the unit-cell parameters and twisting bond angles as a result. The effect of these structural changes on the magnetism are to lower the T_C by a considerable degree, on the relative low-temperature scale. While naively, one may expect that the chemical pressure serves to bring the Ni ions closer together, which it does, and to enhance the exchange interactions as a result. This would be true if direct exchange were the responsible mechanism. However, it is clear from the change in the sign of the exchange between Ba₂La₂NiW₂O₁₂ and Ba₂La₂NiTe₂O₁₂, that direct exchange is not responsible. Therefore, the bending of the bond angles, and its implications for the longer-range indirect exchange mechanisms must be the cause. The reduced T_C can then be considered as weakening of the FM exchange as a result of the less ideal bond angles, it can be considered as a strengthening of the competing AFM Ni–O–O–Ni mechanism, which manifests in the ground state of Ba₂La₂NiTe₂O₁₂, or as a combination of the two effects.

Supporting information

Figure S1. DOI: https://doi.org/10.1107/S2052520624007091/dv5014sup2.pdf

Crystal structure: contains datablocks SR2LA2NIW2O12_SYNCH4_publ, SR2LA2NIW2O12_SYNCH4_overall, SR2LA2NIW2O12_SYNCH4_phase_1, SR2LA2NIW2O12_SYNCH4_phase_2, SR2LA2NIW2O12_SYNCH4_phase_3, SR2LA2NIW2O12_SYNCH4_phase_4, SR2LA2NIW2O12_SYNCH4_phase_5, SR2LA2NIW2O12_SYNCH4_p_05. DOI: https://doi.org/10.1107/S2052520624007091/dv5014sup2.cif

Computing details top

(SR2LA2NIW2O12_SYNCH4_phase_1) top

Crystal data top

La₂NiO₁₂Sr₂W₂	c = 26.5639 (6) Å
M_r = 1071.44	V = 719.56 (3) Å³
Trigonal, R3	Z = 3
a = 5.59270 (8) Å

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
SR1	0.0	0.0	0.13430 (16)	0.00534
LA2	0.0	0.0	0.29173 (13)	0.01114
NI3	0.0	0.0	0.0	0.00656
W4	0.0	0.0	0.42188 (10)	0.00775
O5	0.460 (9)	0.467 (9)	0.1238 (4)	0.04418
O6	0.422 (3)	0.462 (3)	0.2910 (5)	0.07198

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
SR1	0.0023 (11)	0.0023 (11)	0.012 (3)	0.0011 (6)	0.0	0.0
LA2	0.0047 (16)	0.0047 (16)	0.024 (2)	0.0024 (8)	0.0	0.0
NI3	0.013 (5)	0.013 (5)	−0.007 (5)	0.007 (2)	0.0	0.0
W4	0.0043 (9)	0.0043 (9)	0.0146 (14)	0.0022 (5)	0.0	0.0
O5	0.08 (3)	0.07 (2)	0.013 (12)	0.06 (2)	−0.054 (16)	−0.032 (16)
O6	0.062 (19)	0.036 (15)	−0.008 (12)	−0.070 (9)	−0.011 (8)	0.011 (8)

Geometric parameters (Å, º) top

SR1—SR1ⁱ	3.658 (4)	LA2—O6^x	2.478 (16)
SR1—SR1ⁱⁱ	3.658 (4)	LA2—O6^xi	3.128 (16)
SR1—SR1ⁱⁱⁱ	3.658 (4)	LA2—O6^xvi	2.665 (14)
SR1—LA2	4.182 (7)	LA2—O6^xx	2.665 (14)
SR1—LA2ⁱ	4.061 (2)	LA2—O6^xxi	2.665 (14)
SR1—LA2ⁱⁱ	4.061 (2)	NI3—SR1	3.568 (4)
SR1—LA2ⁱⁱⁱ	4.061 (2)	NI3—SR1^xxii	3.568 (4)
SR1—NI3	3.568 (4)	NI3—LA2^iv	3.4128 (11)
SR1—W4^iv	3.450 (2)	NI3—LA2^v	3.4128 (11)
SR1—W4^v	3.450 (2)	NI3—LA2^vi	3.4128 (11)
SR1—W4^vi	3.450 (2)	NI3—LA2ⁱ	3.4128 (11)
SR1—O5^vii	3.01 (5)	NI3—LA2ⁱⁱ	3.4128 (11)
SR1—O5	2.61 (5)	NI3—LA2ⁱⁱⁱ	3.4128 (11)
SR1—O5^viii	2.61 (5)	NI3—O6^iv	2.153 (14)
SR1—O5^ix	3.01 (5)	NI3—O6^xxiii	2.153 (14)
SR1—O5^x	2.61 (5)	NI3—O6^xxiv	2.153 (14)
SR1—O5^xi	3.01 (5)	NI3—O6ⁱⁱⁱ	2.153 (14)
SR1—O5ⁱⁱⁱ	2.602 (12)	NI3—O6^xii	2.153 (14)
SR1—O5^xii	2.602 (12)	NI3—O6^xiii	2.153 (14)
SR1—O5^xiii	2.602 (12)	W4—SR1^xvii	3.450 (2)
SR1—O6ⁱⁱⁱ	3.056 (14)	W4—SR1^xviii	3.450 (2)
SR1—O6^xii	3.056 (14)	W4—SR1^xix	3.450 (2)
SR1—O6^xiii	3.056 (14)	W4—LA2	3.457 (2)
LA2—SR1	4.182 (7)	W4—LA2^xiv	3.461 (2)
LA2—SR1ⁱ	4.061 (2)	W4—LA2^xv	3.461 (2)
LA2—SR1ⁱⁱ	4.061 (2)	W4—LA2^xvi	3.461 (2)
LA2—SR1ⁱⁱⁱ	4.061 (2)	W4—O5^xvii	1.845 (13)
LA2—LA2^xiv	3.913 (4)	W4—O5^xxv	1.845 (13)
LA2—LA2^xv	3.913 (4)	W4—O5^xxvi	1.845 (13)
LA2—LA2^xvi	3.913 (4)	W4—O6^xvi	1.906 (13)
LA2—NI3^xvii	3.4128 (11)	W4—O6^xx	1.906 (13)
LA2—NI3^xviii	3.4128 (11)	W4—O6^xxi	1.906 (13)
LA2—NI3^xix	3.4128 (11)	O5—SR1	2.61 (5)
LA2—W4	3.457 (2)	O5—SR1^xxvii	3.01 (5)
LA2—W4^xiv	3.461 (2)	O5—SR1ⁱⁱⁱ	2.602 (12)
LA2—W4^xv	3.461 (2)	O5—LA2ⁱⁱⁱ	2.745 (14)
LA2—W4^xvi	3.461 (2)	O5—W4^vi	1.845 (13)
LA2—O5ⁱⁱⁱ	2.745 (14)	O6—SR1ⁱⁱⁱ	3.056 (14)
LA2—O5^xii	2.745 (14)	O6—LA2	2.478 (16)
LA2—O5^xiii	2.745 (14)	O6—LA2^xxvii	3.128 (16)
LA2—O6^vii	3.128 (16)	O6—LA2^xvi	2.665 (14)
LA2—O6	2.478 (16)	O6—NI3^xix	2.153 (14)
LA2—O6^viii	2.478 (16)	O6—W4^xvi	1.906 (13)
LA2—O6^ix	3.128 (16)

SR1ⁱ—SR1—SR1ⁱⁱ	99.71 (15)	O5^x—SR1—O5^xi	168.4 (5)
SR1ⁱ—SR1—SR1ⁱⁱⁱ	99.71 (15)	O5^x—SR1—O5ⁱⁱⁱ	64.5 (9)
SR1ⁱ—SR1—W4^iv	75.674 (19)	O5^x—SR1—O5^xii	131.7 (8)
SR1ⁱ—SR1—W4^v	75.674 (19)	O5^x—SR1—O5^xiii	90.8 (10)
SR1ⁱ—SR1—W4^vi	172.6 (2)	O5^xi—SR1—O5ⁱⁱⁱ	125.1 (8)
SR1ⁱ—SR1—O5^vii	44.6 (2)	O5^xi—SR1—O5^xii	58.8 (8)
SR1ⁱ—SR1—O5	144.8 (3)	O5^xi—SR1—O5^xiii	99.1 (10)
SR1ⁱ—SR1—O5^viii	92.2 (3)	O5ⁱⁱⁱ—SR1—O5^xii	67.3 (5)
SR1ⁱ—SR1—O5^ix	91.9 (3)	O5ⁱⁱⁱ—SR1—O5^xiii	67.3 (5)
SR1ⁱ—SR1—O5^x	45.3 (3)	O5^xii—SR1—O5^xiii	67.3 (5)
SR1ⁱ—SR1—O5^xi	144.1 (3)	O5ⁱⁱⁱ—LA2—O5^xii	63.4 (4)
SR1ⁱ—SR1—O5ⁱⁱⁱ	54.4 (11)	O5ⁱⁱⁱ—LA2—O5^xiii	63.4 (4)
SR1ⁱ—SR1—O5^xii	101.5 (4)	O5ⁱⁱⁱ—LA2—O6	88.1 (11)
SR1ⁱ—SR1—O5^xiii	45.5 (11)	O5ⁱⁱⁱ—LA2—O6^viii	122.1 (7)
SR1ⁱⁱ—SR1—SR1ⁱⁱⁱ	99.71 (15)	O5ⁱⁱⁱ—LA2—O6^x	58.9 (6)
SR1ⁱⁱ—SR1—W4^iv	75.674 (19)	O5ⁱⁱⁱ—LA2—O6^xvi	167.8 (9)
SR1ⁱⁱ—SR1—W4^v	172.6 (2)	O5ⁱⁱⁱ—LA2—O6^xx	127.4 (7)
SR1ⁱⁱ—SR1—W4^vi	75.674 (19)	O5ⁱⁱⁱ—LA2—O6^xxi	114.3 (6)
SR1ⁱⁱ—SR1—O5^vii	91.9 (3)	O5^xii—LA2—O5^xiii	63.4 (4)
SR1ⁱⁱ—SR1—O5	92.2 (3)	O5^xii—LA2—O6	58.9 (6)
SR1ⁱⁱ—SR1—O5^viii	45.3 (3)	O5^xii—LA2—O6^viii	88.1 (11)
SR1ⁱⁱ—SR1—O5^ix	144.1 (3)	O5^xii—LA2—O6^x	122.1 (7)
SR1ⁱⁱ—SR1—O5^x	144.8 (3)	O5^xii—LA2—O6^xvi	114.3 (6)
SR1ⁱⁱ—SR1—O5^xi	44.6 (2)	O5^xii—LA2—O6^xx	167.8 (9)
SR1ⁱⁱ—SR1—O5ⁱⁱⁱ	101.5 (4)	O5^xii—LA2—O6^xxi	127.4 (7)
SR1ⁱⁱ—SR1—O5^xii	45.5 (11)	O5^xiii—LA2—O6	122.1 (7)
SR1ⁱⁱ—SR1—O5^xiii	54.4 (11)	O5^xiii—LA2—O6^viii	58.9 (6)
SR1ⁱⁱⁱ—SR1—W4^iv	172.6 (2)	O5^xiii—LA2—O6^x	88.1 (11)
SR1ⁱⁱⁱ—SR1—W4^v	75.674 (19)	O5^xiii—LA2—O6^xvi	127.4 (7)
SR1ⁱⁱⁱ—SR1—W4^vi	75.674 (19)	O5^xiii—LA2—O6^xx	114.3 (6)
SR1ⁱⁱⁱ—SR1—O5^vii	144.1 (3)	O5^xiii—LA2—O6^xxi	167.8 (9)
SR1ⁱⁱⁱ—SR1—O5	45.3 (3)	O6—LA2—O6^viii	119.994 (8)
SR1ⁱⁱⁱ—SR1—O5^viii	144.8 (3)	O6—LA2—O6^x	119.994 (8)
SR1ⁱⁱⁱ—SR1—O5^ix	44.6 (2)	O6—LA2—O6^xvi	81.0 (5)
SR1ⁱⁱⁱ—SR1—O5^x	92.2 (3)	O6—LA2—O6^xx	122.8 (3)
SR1ⁱⁱⁱ—SR1—O5^xi	91.9 (3)	O6—LA2—O6^xxi	68.7 (5)
SR1ⁱⁱⁱ—SR1—O5ⁱⁱⁱ	45.5 (11)	O6^viii—LA2—O6^x	119.994 (8)
SR1ⁱⁱⁱ—SR1—O5^xii	54.4 (11)	O6^viii—LA2—O6^xvi	68.7 (5)
SR1ⁱⁱⁱ—SR1—O5^xiii	101.5 (4)	O6^viii—LA2—O6^xx	81.0 (5)
W4^iv—SR1—W4^v	108.29 (10)	O6^viii—LA2—O6^xxi	122.8 (3)
W4^iv—SR1—W4^vi	108.29 (10)	O6^x—LA2—O6^xvi	122.8 (3)
W4^iv—SR1—O5^vii	32.3 (2)	O6^x—LA2—O6^xx	68.7 (5)
W4^iv—SR1—O5	139.6 (3)	O6^x—LA2—O6^xxi	81.0 (5)
W4^iv—SR1—O5^viii	31.8 (3)	O6^xvi—LA2—O6^xx	56.6 (5)
W4^iv—SR1—O5^ix	140.2 (3)	O6^xvi—LA2—O6^xxi	56.6 (5)
W4^iv—SR1—O5^x	88.6 (3)	O6^xx—LA2—O6^xxi	56.6 (5)
W4^iv—SR1—O5^xi	88.8 (3)	SR1^xvii—W4—SR1^xviii	108.29 (10)
W4^iv—SR1—O5ⁱⁱⁱ	129.2 (11)	SR1^xvii—W4—SR1^xix	108.29 (10)
W4^iv—SR1—O5^xii	120.3 (11)	SR1^xvii—W4—O5^xvii	48.1 (15)
W4^iv—SR1—O5^xiii	71.1 (3)	SR1^xvii—W4—O5^xxv	128.4 (5)
W4^v—SR1—W4^vi	108.29 (10)	SR1^xvii—W4—O5^xxvi	60.7 (15)
W4^v—SR1—O5^vii	88.8 (3)	SR1^xvii—W4—O6^xvi	135.6 (5)
W4^v—SR1—O5	88.6 (3)	SR1^xvii—W4—O6^xx	61.9 (4)
W4^v—SR1—O5^viii	139.6 (3)	SR1^xvii—W4—O6^xxi	115.9 (5)
W4^v—SR1—O5^ix	32.3 (2)	SR1^xviii—W4—SR1^xix	108.29 (10)
W4^v—SR1—O5^x	31.8 (3)	SR1^xviii—W4—O5^xvii	128.4 (5)
W4^v—SR1—O5^xi	140.2 (3)	SR1^xviii—W4—O5^xxv	60.7 (15)
W4^v—SR1—O5ⁱⁱⁱ	71.1 (3)	SR1^xviii—W4—O5^xxvi	48.1 (15)
W4^v—SR1—O5^xii	129.2 (11)	SR1^xviii—W4—O6^xvi	61.9 (4)
W4^v—SR1—O5^xiii	120.3 (11)	SR1^xviii—W4—O6^xx	115.9 (5)
W4^vi—SR1—O5^vii	140.2 (3)	SR1^xviii—W4—O6^xxi	135.6 (5)
W4^vi—SR1—O5	31.8 (3)	SR1^xix—W4—O5^xvii	60.7 (15)
W4^vi—SR1—O5^viii	88.6 (3)	SR1^xix—W4—O5^xxv	48.1 (15)
W4^vi—SR1—O5^ix	88.8 (3)	SR1^xix—W4—O5^xxvi	128.4 (5)
W4^vi—SR1—O5^x	139.6 (3)	SR1^xix—W4—O6^xvi	115.9 (5)
W4^vi—SR1—O5^xi	32.3 (2)	SR1^xix—W4—O6^xx	135.6 (5)
W4^vi—SR1—O5ⁱⁱⁱ	120.3 (11)	SR1^xix—W4—O6^xxi	61.9 (4)
W4^vi—SR1—O5^xii	71.1 (3)	O5^xvii—W4—O5^xxv	96.6 (6)
W4^vi—SR1—O5^xiii	129.2 (11)	O5^xvii—W4—O5^xxvi	96.6 (6)
O5^vii—SR1—O5	168.4 (5)	O5^xvii—W4—O6^xvi	169.4 (9)
O5^vii—SR1—O5^viii	58.1 (6)	O5^xvii—W4—O6^xx	93.0 (13)
O5^vii—SR1—O5^ix	119.15 (8)	O5^xvii—W4—O6^xxi	86.7 (11)
O5^vii—SR1—O5^x	61.2 (6)	O5^xxv—W4—O5^xxvi	96.6 (6)
O5^vii—SR1—O5^xi	119.15 (8)	O5^xxv—W4—O6^xvi	86.7 (11)
O5^vii—SR1—O5ⁱⁱⁱ	99.1 (10)	O5^xxv—W4—O6^xx	169.4 (9)
O5^vii—SR1—O5^xii	125.1 (8)	O5^xxv—W4—O6^xxi	93.0 (13)
O5^vii—SR1—O5^xiii	58.8 (8)	O5^xxvi—W4—O6^xvi	93.0 (13)
O5—SR1—O5^viii	118.86 (10)	O5^xxvi—W4—O6^xx	86.7 (11)
O5—SR1—O5^ix	61.2 (6)	O5^xxvi—W4—O6^xxi	169.4 (9)
O5—SR1—O5^x	118.86 (10)	O6^xvi—W4—O6^xx	83.0 (7)
O5—SR1—O5^xi	58.1 (6)	O6^xvi—W4—O6^xxi	83.0 (7)
O5—SR1—O5ⁱⁱⁱ	90.8 (10)	O6^xx—W4—O6^xxi	83.0 (7)
O5—SR1—O5^xii	64.5 (9)	SR1—O5—SR1^xxvii	168.4 (5)
O5—SR1—O5^xiii	131.7 (8)	SR1—O5—SR1ⁱⁱⁱ	89.2 (10)
O5^viii—SR1—O5^ix	168.4 (5)	SR1—O5—LA2ⁱⁱⁱ	98.7 (11)
O5^viii—SR1—O5^x	118.86 (10)	SR1—O5—W4^vi	100.2 (16)
O5^viii—SR1—O5^xi	61.2 (6)	SR1^xxvii—O5—SR1ⁱⁱⁱ	80.9 (10)
O5^viii—SR1—O5ⁱⁱⁱ	131.7 (8)	SR1^xxvii—O5—LA2ⁱⁱⁱ	89.6 (11)
O5^viii—SR1—O5^xii	90.8 (10)	SR1^xxvii—O5—W4^vi	87.0 (16)
O5^viii—SR1—O5^xiii	64.5 (9)	SR1ⁱⁱⁱ—O5—LA2ⁱⁱⁱ	102.9 (5)
O5^ix—SR1—O5^x	58.1 (6)	SR1ⁱⁱⁱ—O5—W4^vi	157.5 (14)
O5^ix—SR1—O5^xi	119.15 (8)	LA2ⁱⁱⁱ—O5—W4^vi	95.9 (5)
O5^ix—SR1—O5ⁱⁱⁱ	58.8 (8)	LA2—O6—LA2^xvi	99.0 (5)
O5^ix—SR1—O5^xii	99.1 (10)	LA2—O6—W4^xvi	103.5 (6)
O5^ix—SR1—O5^xiii	125.1 (8)	LA2^xvi—O6—W4^xvi	96.9 (6)

Symmetry codes: (i) −x−5/3, −y−4/3, −z−1/3; (ii) −x−5/3, −y−1/3, −z−1/3; (iii) −x−2/3, −y−1/3, −z−1/3; (iv) x−2/3, y−1/3, z−1/3; (v) x+1/3, y−1/3, z−1/3; (vi) x+1/3, y+2/3, z−1/3; (vii) x−1, y−1, z; (viii) −y, x−y, z; (ix) −y+1, x−y, z; (x) y−x, −x, z; (xi) y−x, −x+1, z; (xii) y−5/3, y−x−1/3, −z−1/3; (xiii) x−y−5/3, x−4/3, −z−1/3; (xiv) −x−4/3, −y−5/3, −z−2/3; (xv) −x−1/3, −y−5/3, −z−2/3; (xvi) −x−1/3, −y−2/3, −z−2/3; (xvii) x−1/3, y−2/3, z+1/3; (xviii) x−1/3, y+1/3, z+1/3; (xix) x+2/3, y+1/3, z+1/3; (xx) y−4/3, y−x−5/3, −z−2/3; (xxi) x−y−1/3, x−5/3, −z−2/3; (xxii) −x, −y, −z; (xxiii) −y+1/3, x−y−1/3, z−1/3; (xxiv) y−x+1/3, −x+2/3, z−1/3; (xxv) −y+2/3, x−y+1/3, z+1/3; (xxvi) y−x−1/3, −x+1/3, z+1/3; (xxvii) x+1, y+1, z.

(SR2LA2NIW2O12_SYNCH4_phase_2) top

Crystal data top

La₂O₃	c = 6.1345 (8) Å
M_r = 325.81	V = 82.55 (1) Å³
Hexagonal, P6₃/mmc	Z = 2
a = 3.9418 (3) Å

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
La1	0.3333	0.6667	0.22956	0.00263*
O1	0.0	0.0	0.0	0.01*
O2	0.3333	0.6667	0.6421	0.01*

Geometric parameters (Å, º) top

La1—La1ⁱ	3.9418 (3)	La1—O1^xii	2.8164 (2)
La1—La1ⁱⁱ	3.9418 (3)	La1—O2	2.5307 (3)
La1—La1ⁱⁱⁱ	3.9418 (3)	La1—O2^vii	2.3383 (2)
La1—La1^iv	3.9418 (3)	La1—O2^ix	2.3383 (2)
La1—La1^v	3.9418 (3)	La1—O2^xi	2.3380 (2)
La1—La1^vi	3.9418 (3)	La1—O2^xiv	2.4079 (2)
La1—La1^vii	3.8194 (3)	La1—O2^xvi	2.4086 (2)
La1—La1^viii	3.8194 (3)	La1—O2^xviii	2.4079 (2)
La1—La1^ix	3.8194 (3)	La1—O2^xxii	2.2799 (3)
La1—La1^x	3.8194 (3)	O1—La1ⁱ	2.6764 (2)
La1—La1^xi	3.8192 (3)	O1—La1ⁱⁱⁱ	2.6761 (2)
La1—La1^xii	3.8192 (3)	O1—La1	2.6764 (2)
La1—La1^xiii	3.6209 (3)	O1—La1^xxvii	2.8164 (2)
La1—La1^xiv	4.0234 (4)	O1—La1^vii	2.8164 (2)
La1—La1^xv	3.6213 (3)	O1—La1^ix	2.8161 (2)
La1—La1^xvi	4.0237 (4)	O1—La1^xxviii	2.6764 (2)
La1—La1^xvii	3.6209 (3)	O1—La1^xiii	2.6761 (2)
La1—La1^xviii	4.0234 (4)	O1—La1^xv	2.6764 (2)
La1—La1^xix	3.9496 (3)	O1—La1^xix	2.8161 (2)
La1—La1^xx	3.9494 (3)	O1—La1^xxi	2.8164 (2)
La1—La1^xxi	3.9500 (3)	O1—La1^xxii	2.8164 (2)
La1—La1^xxii	0.2508 (1)	O2—La1	2.5307 (3)
La1—La1^xxiii	3.9496 (3)	O2—La1^viii	2.3383 (2)
La1—La1^xxiv	3.9502 (3)	O2—La1^x	2.3383 (2)
La1—La1^xxv	3.9500 (3)	O2—La1^xii	2.3380 (2)
La1—O1	2.6764 (2)	O2—La1^xiv	2.4079 (2)
La1—O1^iv	2.6761 (2)	O2—La1^xvi	2.4086 (2)
La1—O1^vi	2.6764 (2)	O2—La1^xviii	2.4079 (2)
La1—O1^viii	2.8164 (2)	O2—La1^xxii	2.2799 (3)
La1—O1^xxvi	2.8161 (2)	O2—O2^xxix	1.3238 (2)

La1^xiii—La1—La1^xv	65.952 (7)	O2—La1—O2^ix	103.2645 (19)
La1^xiii—La1—La1^xvii	65.957 (7)	O2—La1—O2^xi	103.2664 (19)
La1^xiii—La1—La1^xxii	141.141 (4)	O2—La1—O2^xiv	70.916 (3)
La1^xiii—La1—O1	47.427 (3)	O2—La1—O2^xvi	70.921 (3)
La1^xiii—La1—O1^iv	47.434 (3)	O2—La1—O2^xviii	70.916 (3)
La1^xiii—La1—O1^vi	97.190 (8)	O2—La1—O2^xxii	180.0
La1^xiii—La1—O2	141.063 (4)	O2^vii—La1—O2^ix	114.8907 (14)
La1^xiii—La1—O2^vii	37.799 (2)	O2^vii—La1—O2^xi	114.9035 (14)
La1^xiii—La1—O2^ix	97.310 (4)	O2^vii—La1—O2^xiv	32.349 (4)
La1^xiii—La1—O2^xi	97.322 (4)	O2^vii—La1—O2^xvi	122.3343 (7)
La1^xiii—La1—O2^xiv	70.147 (7)	O2^vii—La1—O2^xviii	122.3534 (7)
La1^xiii—La1—O2^xvi	123.4449 (12)	O2^vii—La1—O2^xxii	76.7441 (19)
La1^xiii—La1—O2^xviii	123.4673 (12)	O2^ix—La1—O2^xi	114.9035 (14)
La1^xiii—La1—O2^xxii	38.946 (4)	O2^ix—La1—O2^xiv	122.3253 (7)
La1^xv—La1—La1^xvii	65.952 (7)	O2^ix—La1—O2^xvi	32.343 (4)
La1^xv—La1—La1^xxii	140.977 (4)	O2^ix—La1—O2^xviii	122.3347 (7)
La1^xv—La1—O1	47.427 (3)	O2^ix—La1—O2^xxii	76.7269 (19)
La1^xv—La1—O1^iv	97.195 (8)	O2^xi—La1—O2^xiv	122.3492 (7)
La1^xv—La1—O1^vi	47.427 (3)	O2^xi—La1—O2^xvi	122.3395 (7)
La1^xv—La1—O2	141.055 (4)	O2^xi—La1—O2^xviii	32.351 (4)
La1^xv—La1—O2^vii	97.320 (4)	O2^xi—La1—O2^xxii	76.7336 (19)
La1^xv—La1—O2^ix	37.790 (2)	O2^xiv—La1—O2^xvi	109.850 (3)
La1^xv—La1—O2^xi	97.321 (4)	O2^xiv—La1—O2^xviii	109.872 (3)
La1^xv—La1—O2^xiv	123.4506 (12)	O2^xiv—La1—O2^xxii	109.093 (3)
La1^xv—La1—O2^xvi	70.134 (7)	O2^xvi—La1—O2^xviii	109.850 (3)
La1^xv—La1—O2^xviii	123.4506 (12)	O2^xvi—La1—O2^xxii	109.070 (3)
La1^xv—La1—O2^xxii	38.937 (4)	O2^xviii—La1—O2^xxii	109.084 (3)
La1^xvii—La1—La1^xxii	141.063 (4)	La1ⁱ—O1—La1ⁱⁱⁱ	94.860 (5)
La1^xvii—La1—O1	97.190 (8)	La1ⁱ—O1—La1	94.854 (5)
La1^xvii—La1—O1^iv	47.434 (3)	La1ⁱ—O1—La1^xxviii	85.146 (5)
La1^xvii—La1—O1^vi	47.427 (3)	La1ⁱ—O1—La1^xiii	85.140 (5)
La1^xvii—La1—O2	141.063 (4)	La1ⁱ—O1—La1^xv	180.0
La1^xvii—La1—O2^vii	97.326 (4)	La1ⁱⁱⁱ—O1—La1	94.860 (5)
La1^xvii—La1—O2^ix	97.315 (4)	La1ⁱⁱⁱ—O1—La1^xxviii	85.140 (5)
La1^xvii—La1—O2^xi	37.797 (2)	La1ⁱⁱⁱ—O1—La1^xiii	180.0
La1^xvii—La1—O2^xiv	123.4673 (12)	La1ⁱⁱⁱ—O1—La1^xv	85.140 (5)
La1^xvii—La1—O2^xvi	123.4449 (12)	La1—O1—La1^xxviii	180.0
La1^xvii—La1—O2^xviii	70.147 (7)	La1—O1—La1^xiii	85.140 (5)
La1^xvii—La1—O2^xxii	38.937 (4)	La1—O1—La1^xv	85.146 (5)
La1^xxii—La1—O1	121.747 (4)	La1^xxviii—O1—La1^xiii	94.860 (5)
La1^xxii—La1—O1^iv	121.829 (4)	La1^xxviii—O1—La1^xv	94.854 (5)
La1^xxii—La1—O1^vi	121.669 (4)	La1^xiii—O1—La1^xv	94.860 (5)
La1^xxii—La1—O2	0.0	La1—O2—La1^viii	103.2645 (19)
La1^xxii—La1—O2^vii	103.3425 (19)	La1—O2—La1^x	103.2645 (19)
La1^xxii—La1—O2^ix	103.1865 (19)	La1—O2—La1^xii	103.2664 (19)
La1^xxii—La1—O2^xi	103.2664 (19)	La1—O2—La1^xiv	109.084 (3)
La1^xxii—La1—O2^xiv	70.994 (3)	La1—O2—La1^xvi	109.079 (3)
La1^xxii—La1—O2^xvi	70.843 (3)	La1—O2—La1^xviii	109.084 (3)
La1^xxii—La1—O2^xviii	70.916 (3)	La1—O2—La1^xxii	0.0
La1^xxii—La1—O2^xxii	180.0	La1—O2—O2^xxix	180.0
O1—La1—O1^iv	94.860 (5)	La1^viii—O2—La1^x	114.8907 (14)
O1—La1—O1^vi	94.854 (5)	La1^viii—O2—La1^xii	114.9035 (14)
O1—La1—O2	121.747 (4)	La1^viii—O2—La1^xiv	5.8198 (7)
O1—La1—O2^vii	57.6850 (7)	La1^viii—O2—La1^xvi	112.6350 (19)
O1—La1—O2^ix	57.6765 (7)	La1^viii—O2—La1^xviii	112.650 (2)
O1—La1—O2^xi	134.987 (6)	La1^viii—O2—La1^xxii	103.2731 (19)
O1—La1—O2^xiv	76.712 (4)	La1^viii—O2—O2^xxix	76.7503 (19)
O1—La1—O2^xvi	76.709 (4)	La1^x—O2—La1^xii	114.9035 (14)
O1—La1—O2^xviii	167.3373 (12)	La1^x—O2—La1^xiv	112.6243 (19)
O1—La1—O2^xxii	58.253 (4)	La1^x—O2—La1^xvi	5.8145 (7)
O1^iv—La1—O1^vi	94.860 (5)	La1^x—O2—La1^xviii	112.6328 (19)
O1^iv—La1—O2	121.751 (4)	La1^x—O2—La1^xxii	103.2559 (19)
O1^iv—La1—O2^vii	57.6894 (7)	La1^x—O2—O2^xxix	76.7207 (19)
O1^iv—La1—O2^ix	134.985 (6)	La1^xii—O2—La1^xiv	112.645 (2)
O1^iv—La1—O2^xi	57.6843 (7)	La1^xii—O2—La1^xvi	112.6384 (19)
O1^iv—La1—O2^xiv	76.725 (4)	La1^xii—O2—La1^xviii	5.8179 (7)
O1^iv—La1—O2^xvi	167.3282 (12)	La1^xii—O2—La1^xxii	103.2664 (19)
O1^iv—La1—O2^xviii	76.725 (4)	La1^xii—O2—O2^xxix	76.7336 (19)
O1^iv—La1—O2^xxii	58.258 (4)	La1^xiv—O2—La1^xvi	109.850 (3)
O1^vi—La1—O2	121.747 (4)	La1^xiv—O2—La1^xviii	109.872 (3)
O1^vi—La1—O2^vii	134.988 (6)	La1^xiv—O2—La1^xxii	109.093 (3)
O1^vi—La1—O2^ix	57.6850 (7)	La1^xiv—O2—O2^xxix	70.931 (3)
O1^vi—La1—O2^xi	57.6882 (7)	La1^xvi—O2—La1^xviii	109.850 (3)
O1^vi—La1—O2^xiv	167.3373 (12)	La1^xvi—O2—La1^xxii	109.070 (3)
O1^vi—La1—O2^xvi	76.709 (4)	La1^xvi—O2—O2^xxix	70.906 (3)
O1^vi—La1—O2^xviii	76.712 (4)	La1^xviii—O2—La1^xxii	109.084 (3)
O1^vi—La1—O2^xxii	58.244 (4)	La1^xviii—O2—O2^xxix	70.916 (3)
O2—La1—O2^vii	103.2645 (19)	La1^xxii—O2—O2^xxix	180.0

Symmetry codes: (i) x−1, y−1, z; (ii) x−1, y, z; (iii) x, y−1, z; (iv) x, y+1, z; (v) x+1, y, z; (vi) x+1, y+1, z; (vii) x−y, x, z−1/2; (viii) x−y, x, z+1/2; (ix) x−y+1, x, z−1/2; (x) x−y+1, x, z+1/2; (xi) x−y+1, x+1, z−1/2; (xii) x−y+1, x+1, z+1/2; (xiii) −x, −y+1, −z; (xiv) −x, −y+1, −z+1; (xv) −x+1, −y+1, −z; (xvi) −x+1, −y+1, −z+1; (xvii) −x+1, −y+2, −z; (xviii) −x+1, −y+2, −z+1; (xix) y−x−1, −x, −z+1/2; (xx) y−x−1, −x+1, −z+1/2; (xxi) y−x, −x, −z+1/2; (xxii) y−x, −x+1, −z+1/2; (xxiii) y−x, −x+2, −z+1/2; (xxiv) y−x+1, −x+1, −z+1/2; (xxv) y−x+1, −x+2, −z+1/2; (xxvi) x−y, x+1, z+1/2; (xxvii) x−y, x−1, z−1/2; (xxviii) −x, −y, −z; (xxix) y−x, −x+1, −z+3/2.

(SR2LA2NIW2O12_SYNCH4_phase_3) top

Crystal data top

OZn	c = 5.2062 (7) Å
M_r = 81.38	V = 47.68 (1) Å³
Hexagonal, P6₃mc	Z = 2
a = 3.2520 (3) Å

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Zn1	0.3333	0.6667	0.01069	0.013*
O1	0.3333	0.6667	0.37181	0.01*

Geometric parameters (Å, º) top

Zn1—O1	1.8801 (3)	O1—Zn1	1.8801 (3)
Zn1—O1ⁱ	2.0120 (2)	O1—Zn1^iv	2.0120 (2)
Zn1—O1ⁱⁱ	2.0120 (2)	O1—Zn1^v	2.0120 (2)
Zn1—O1ⁱⁱⁱ	2.0118 (2)	O1—Zn1^vi	2.0118 (2)

O1—Zn1—O1ⁱ	111.060 (3)	Zn1—O1—Zn1^iv	111.060 (3)
O1—Zn1—O1ⁱⁱ	111.060 (3)	Zn1—O1—Zn1^v	111.060 (3)
O1—Zn1—O1ⁱⁱⁱ	111.063 (3)	Zn1—O1—Zn1^vi	111.063 (3)
O1ⁱ—Zn1—O1ⁱⁱ	107.829 (3)	Zn1^iv—O1—Zn1^v	107.829 (3)
O1ⁱ—Zn1—O1ⁱⁱⁱ	107.839 (3)	Zn1^iv—O1—Zn1^vi	107.839 (3)
O1ⁱⁱ—Zn1—O1ⁱⁱⁱ	107.839 (3)	Zn1^v—O1—Zn1^vi	107.839 (3)

Symmetry codes: (i) x−y, x, z−1/2; (ii) x−y+1, x, z−1/2; (iii) x−y+1, x+1, z−1/2; (iv) x−y, x, z+1/2; (v) x−y+1, x, z+1/2; (vi) x−y+1, x+1, z+1/2.

(SR2LA2NIW2O12_SYNCH4_phase_4) top

Crystal data top

La_0.87O⁻0.91	a = 4.5112 (6) Å
M_r = 106.26	V = 91.81 (3) Å³
Cubic, Im3m	Z = 1

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
La1	0.0	0.0	0.0	0.00402*	0.435
O1	0.0	0.5	0.5	0.003*	-0.152

Geometric parameters (Å, º) top

La1—La1ⁱ	3.9068 (4)	La1—O1ⁱ	2.2556 (3)
La1—La1ⁱⁱ	3.9068 (4)	La1—O1^v	2.2556 (3)
La1—La1ⁱⁱⁱ	3.9068 (4)	La1—O1^ix	2.2556 (3)
La1—La1^iv	3.9068 (4)	La1—O1^x	2.2556 (3)
La1—La1^v	3.9068 (4)	La1—O1^xi	2.2556 (3)
La1—La1^vi	3.9068 (4)	La1—O1^xii	2.2556 (3)
La1—La1^vii	3.9068 (4)	O1—La1^iv	2.2556 (3)
La1—La1^viii	3.9068 (4)	O1—La1^viii	2.2556 (3)

O1ⁱ—La1—O1^v	180.0	O1^v—La1—O1^xii	90.0
O1ⁱ—La1—O1^ix	90.0	O1^ix—La1—O1^x	180.0
O1ⁱ—La1—O1^x	90.0	O1^ix—La1—O1^xi	90.0
O1ⁱ—La1—O1^xi	90.0	O1^ix—La1—O1^xii	90.0
O1ⁱ—La1—O1^xii	90.0	O1^x—La1—O1^xi	90.0
O1^v—La1—O1^ix	90.0	O1^x—La1—O1^xii	90.0
O1^v—La1—O1^x	90.0	O1^xi—La1—O1^xii	180.0
O1^v—La1—O1^xi	90.0	La1^iv—O1—La1^viii	180.0

Symmetry codes: (i) x−1/2, y−1/2, z−1/2; (ii) x−1/2, y−1/2, z+1/2; (iii) x−1/2, y+1/2, z−1/2; (iv) x−1/2, y+1/2, z+1/2; (v) x+1/2, y−1/2, z−1/2; (vi) x+1/2, y−1/2, z+1/2; (vii) x+1/2, y+1/2, z−1/2; (viii) x+1/2, y+1/2, z+1/2; (ix) z−1/2, x−1/2, y−1/2; (x) z−1/2, x+1/2, y−1/2; (xi) y−1/2, z−1/2, x−1/2; (xii) y−1/2, z−1/2, x+1/2.

(SR2LA2NIW2O12_SYNCH4_phase_5) top

Crystal data top

O₄SrW	c = 11.948 (4) Å
M_r = 335.47	V = 350.11 (9) Å³
Tetragonal, I4₁/a	Z = 4
a = 5.4133 (8) Å

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
SR1	0.0	0.25	0.625	0.09371*
W2	0.0	0.25	0.125	0.00322*
O3	0.2362	0.1395	0.0818	0.02*

Geometric parameters (Å, º) top

SR1—SR1ⁱ	4.0309 (7)	SR1—O3^xiv	2.9158 (7)
SR1—SR1ⁱⁱ	4.0309 (7)	SR1—O3^xv	2.5983 (4)
SR1—SR1ⁱⁱⁱ	4.0309 (7)	W2—SR1^xvi	3.8277 (5)
SR1—SR1^iv	4.0309 (7)	W2—SR1^xvii	3.8277 (5)
SR1—W2^v	3.8277 (5)	W2—SR1^xviii	3.8277 (5)
SR1—W2^vi	3.8277 (5)	W2—SR1^xix	3.8277 (5)
SR1—W2^vii	3.8277 (5)	W2—O3	1.5030 (2)
SR1—W2^viii	3.8277 (5)	W2—O3^xx	1.5030 (2)
SR1—O3^vii	2.5983 (4)	W2—O3^xxi	1.5030 (2)
SR1—O3^ix	2.9158 (7)	W2—O3^xxii	1.5030 (2)
SR1—O3^x	2.5983 (4)	O3—SR1^xxiii	2.9158 (7)
SR1—O3^xi	2.9158 (7)	O3—SR1^xviii	2.5983 (4)
SR1—O3^xii	2.5983 (4)	O3—W2	1.5030 (2)
SR1—O3^xiii	2.9158 (7)

SR1ⁱ—SR1—SR1ⁱⁱ	84.362 (19)	O3^vii—SR1—O3^ix	132.726 (5)
SR1ⁱ—SR1—SR1ⁱⁱⁱ	123.307 (11)	O3^vii—SR1—O3^x	92.2615 (15)
SR1ⁱ—SR1—SR1^iv	123.307 (11)	O3^vii—SR1—O3^xxiv	86.237 (5)
SR1ⁱ—SR1—O3^vii	121.0805 (2)	O3^vii—SR1—O3^xii	157.084 (7)
SR1ⁱ—SR1—O3^ix	40.032 (9)	O3^vii—SR1—O3^xxv	70.011 (12)
SR1ⁱ—SR1—O3^x	113.433 (11)	O3^vii—SR1—O3^xiv	74.275 (3)
SR1ⁱ—SR1—O3^xxiv	107.402 (18)	O3^vii—SR1—O3^xxvi	92.2615 (15)
SR1ⁱ—SR1—O3^xii	77.183 (8)	O3^ix—SR1—O3^x	74.275 (3)
SR1ⁱ—SR1—O3^xxv	60.647 (14)	O3^ix—SR1—O3^xxiv	135.895 (11)
SR1ⁱ—SR1—O3^xiv	163.095 (3)	O3^ix—SR1—O3^xii	70.011 (12)
SR1ⁱ—SR1—O3^xxvi	46.205 (3)	O3^ix—SR1—O3^xxv	64.143 (17)
SR1ⁱⁱ—SR1—SR1ⁱⁱⁱ	123.307 (11)	O3^ix—SR1—O3^xiv	135.895 (11)
SR1ⁱⁱ—SR1—SR1^iv	123.307 (11)	O3^ix—SR1—O3^xxvi	86.237 (5)
SR1ⁱⁱ—SR1—O3^vii	77.183 (8)	O3^x—SR1—O3^xxiv	132.726 (5)
SR1ⁱⁱ—SR1—O3^ix	60.647 (14)	O3^x—SR1—O3^xii	92.2615 (15)
SR1ⁱⁱ—SR1—O3^x	46.205 (3)	O3^x—SR1—O3^xxv	86.237 (5)
SR1ⁱⁱ—SR1—O3^xxiv	163.095 (3)	O3^x—SR1—O3^xiv	70.011 (12)
SR1ⁱⁱ—SR1—O3^xii	121.0805 (2)	O3^x—SR1—O3^xxvi	157.084 (7)
SR1ⁱⁱ—SR1—O3^xxv	40.032 (9)	O3^xxiv—SR1—O3^xii	74.275 (3)
SR1ⁱⁱ—SR1—O3^xiv	107.402 (18)	O3^xxiv—SR1—O3^xxv	135.895 (11)
SR1ⁱⁱ—SR1—O3^xxvi	113.433 (11)	O3^xxiv—SR1—O3^xiv	64.143 (17)
SR1ⁱⁱⁱ—SR1—SR1^iv	84.362 (19)	O3^xxiv—SR1—O3^xxvi	70.011 (12)
SR1ⁱⁱⁱ—SR1—O3^vii	46.205 (3)	O3^xii—SR1—O3^xxv	132.726 (5)
SR1ⁱⁱⁱ—SR1—O3^ix	163.095 (3)	O3^xii—SR1—O3^xiv	86.237 (5)
SR1ⁱⁱⁱ—SR1—O3^x	121.0805 (2)	O3^xii—SR1—O3^xxvi	92.2615 (15)
SR1ⁱⁱⁱ—SR1—O3^xxiv	40.032 (9)	O3^xxv—SR1—O3^xiv	135.895 (11)
SR1ⁱⁱⁱ—SR1—O3^xii	113.433 (11)	O3^xxv—SR1—O3^xxvi	74.275 (3)
SR1ⁱⁱⁱ—SR1—O3^xxv	107.402 (18)	O3^xiv—SR1—O3^xxvi	132.726 (5)
SR1ⁱⁱⁱ—SR1—O3^xiv	60.647 (14)	O3—W2—O3^xx	96.773 (4)
SR1ⁱⁱⁱ—SR1—O3^xxvi	77.183 (8)	O3—W2—O3^xxvii	139.831 (12)
SR1^iv—SR1—O3^vii	113.433 (11)	O3—W2—O3^xxviii	96.773 (4)
SR1^iv—SR1—O3^ix	107.402 (18)	O3^xx—W2—O3^xxvii	96.773 (4)
SR1^iv—SR1—O3^x	77.183 (8)	O3^xx—W2—O3^xxviii	139.831 (12)
SR1^iv—SR1—O3^xxiv	60.647 (14)	O3^xxvii—W2—O3^xxviii	96.773 (4)
SR1^iv—SR1—O3^xii	46.205 (3)	SR1^xxiii—O3—SR1^xviii	93.763 (5)
SR1^iv—SR1—O3^xxv	163.095 (3)	SR1^xxiii—O3—W2	128.7545 (14)
SR1^iv—SR1—O3^xiv	40.032 (9)	SR1^xviii—O3—W2	136.242 (7)
SR1^iv—SR1—O3^xxvi	121.0805 (2)

Symmetry codes: (i) −y−1/4, x+1/4, z+1/4; (ii) −y+3/4, x+1/4, z+1/4; (iii) y−1/4, −x−1/4, z−1/4; (iv) y−1/4, −x+3/4, z−1/4; (v) −x−1/2, −y, z+1/2; (vi) −x−1/2, −y+1, z+1/2; (vii) −x+1/2, −y, z+1/2; (viii) −x+1/2, −y+1, z+1/2; (ix) y−1/4, −x+3/4, z+3/4; (x) y+1/4, −x+3/4, −z+3/4; (xi) x−1/2, y, −z+1/2; (xii) x−1/2, y+1/2, z+1/2; (xiii) −y+1/4, x−1/4, z+3/4; (xiv) −x−1/2, −y−1/2, −z−1/2; (xv) −y−5/4, x−5/4, −z−1/4; (xvi) −x−1/2, −y, z−1/2; (xvii) −x−1/2, −y+1, z−1/2; (xviii) −x+1/2, −y, z−1/2; (xix) −x+1/2, −y+1, z−1/2; (xx) −y+1/4, x+1/4, −z+1/4; (xxi) −x, −y+1/2, z; (xxii) y−5/4, −x−3/4, −z−3/4; (xxiii) −y+3/4, x+1/4, z−3/4; (xxiv) x−1/2, y−1, −z+1/2; (xxv) −y−7/4, x−5/4, z−1/4; (xxvi) −y−1/4, x−1/4, −z+3/4; (xxvii) −x−2, −y−1/2, z−2; (xxviii) y−1/4, −x−3/4, −z−3/4.

Acknowledgements

XAS experiments were performed at the BAMline at the BESSY-II storage ring (Helmholtz Center Berlin). We thank the Helmholtz-Zentrum Berlin für Materialien und Energie for the allocation of synchrotron radiation beamtime. We acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Parts of this research were carried out at PETRA III and we would like to thank Ahmed Omar for assistance in using P02.1. Open access funding enabled and organized by Projekt DEAL.

Conflict of interest

The authors declare no competing interests.

Data availability

The authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials.

Funding information

This research was partly supported by the UKRATOP project funded by the Federal Ministry of Education and Research (BMBF) under reference 01DK18002 (to Anastasiia Smerechuk) partially supported by the Deutsche Forschungsgemeinschaft DFG through SFB 1143 (Project-Id 247310070 to Ryan Morrow, Sabine Wurmehl, Bernd Büchner). The following funding is acknowledged: Deutsche Forschungsgemeinschaft (grant No. 247310070); Bundesministerium für Bildung und Forschung (award No. 01DK18002).

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