Isothermal electrocaloric effect in KCI:OH

The entropy of a noninteracting dipole system with the equilibrium dipole moment μ ‖ 〈100〉 in a rigid cubic lattice is obtained for the external electric field E‖ [100] of arbitrary strength, taking into account the 90° tunneling. In thermostating experiments the KCI-OH monocrystals were illuminated with light pulses of rectangular shape (single 10⁻² s shots, absorbed power ranging 3 × 10³ erg/s cm³) and the electric field applied to the crystal was simultaneously removed. The electric field pulse shape, needed for maintaining the crystal temperature constant within some millidegrees at 0.75 K, is close to the theoretical one assuming a “working” dipole number N_E ≈ 0.1N_opt.