2D nanomaterials have been receiving increasing interest from the basic physical sciences to material engineering owing to their variant properties and diverging fields of uses in sensors, electronics, optoelectronics, energy storage devices such as solar cells, lithium batteries, composites, etc. Graphene is the pioneer of a family of 2D materials that has triggered active research. In addition to graphene, many other members, such as boron nitride nanosheets (BNNS), MXenes, and 2D oxide/hydroxide materials, black phosphorous (BP), transition metal dichalcogenides (TMDC), and mono-elemental 2D semiconductors, have joined the family of 2D nanomaterials.

2D nanomaterials have a very low thickness as well as macroscale/nanoscale dimensions, making them the thinnest of all the nanomaterials. They have strong in-plane bonds and weak interlayered van der Waals (vdW) forces. The upper- and lower-layer neighboring atoms are arranged in a different manner. They are configured in a honeycomb structure.

Another aspect of 2D materials is the ease of production of 2D magnetic materials. On decreasing the thickness of 2D nanomaterials to a few sheets, they exhibit a magnetic ground state irrespective of either their antiferromagnetic or ferromagnetic states. The exceptional properties of 2D nanomaterials and their potential applications are largely dependent on their crystal structures. The crystal structures determine the inherent optical, electrical, magnetic, and mechanical properties. Therefore, an in-depth study of the crystal structures of 2D nanomaterials is of great importance. In this chapter, an attempt has been made to summarize the crystal structures of various 2D nanomaterials and their correlation to the magnetic and mechanical properties of these materials.