Ferrimagnetic phase transition in the system Li0.5Fe2.52−x GaxO4 in the vicinity of the multicritical point of the x-T phase diagram

Abstract

In connection with the problem of identifying magnetic states in the vicinity of x0 (the multicritical point of the x-T diagrams of spin-glass systems) a study has been made of properties that can be exploited to determine the presence of a thermodynamic phase transition at the Curie point TC and the distinctive features of the transition, specifically, the temperature dependence of the magnetic part of the specific heat Cm(T), the temperature dependence of the low-field magnetization σH(T), and (with a view toward examining critical behavior in a magnetic field) the magnetization isotherms σH(T). The investigated object is the system of dilute ferrimagnetic spinels Li0.5Fe2.5−xGaxO4, in which every type of magnetic state has spatially inhomogeneous cluster structures. The results obtained for a sample with x=1.45 indicate that the classical criteria of a ferrimagnetic second-order phase transition at TC=(97±2) K occur for x∼x0. The results of similar investigations for a sample with x=1.6, which exists in the cluster spin-glass state for T Tf, are also given for comparison with the preceding case.