First-order phase transition to a reentrant state in a dilute anisotropic ferrimagnet

The temperature dependence of the magnetic contribution to the specific heat of the anisotropic reentrant ferromagnet Li_0.475Co_0.05Fe_1.575Ga_0.9O₄ with freezing temperature T _f =80 K is investigated. It is found that for both T<T _f and T T _f right up to T∼150 K the function C _m (T) is described by the spin-wave law T ^3/2, but an anomaly, exhibiting features which are characteristic for a first-order thermodynamic phase transition, is observed in C _m (T ^3/2) at T=T _f . Pis’ma Zh. éksp. Teor. Fiz. 64, No. 6, 412–415 (25 September 1996)