Specific features of magnetocaloric effect in isotropic antiferromagnets

Abstract

The molecular-field method has been used to study the magnetocaloric effect and the dependence of the magnetic entropy on an external magnetic field in a two-sublattice isotropic antiferromagnet. It has been shown that, for an isotropic antiferromagnet, the magnetization of a canted phase that arises after a spin-flop transition in an applied magnetic field is temperature-independent. Therefore, the magnetic entropy of the phase is independent of the strength of an external field and no magnetocaloric effect is observed. The dependence of the magnetic entropy on the magnetic field and the normal magnetocaloric effect appear only after the spin-flip transition of the antiferromagnet into a magnetic-field-induced ferromagnetic phase. In moderate magnetic fields, this occurs in fact only in the temperature range of T ≥ TN, where TN is the Neel temperature.