Temperature dependence of the heat capacity and saturation magnetization of dilute reentrant ferrimagnetic spinels

Abstract

Using model objects consisting of dilute reentrant spinels Li0.5Fe2.5−xGaxO4 with x=1.0–1.2, this paper describes the temperature dependence of the magnetic contribution to the heat capacity, Cm(T), at H=0 and temperatures exceeding the freezing temperature (Tf∼10 K) and, for T⩾4.2 K, the low-field magnetization σH(T) and the saturation magnetization σS(T), as well as the magnetization isotherms σT(T) in fields of up to 10 kOe. The specific features of the behavior of the overall characteristics of Cm(T) and σS(T) are found for the states of a frustrated ferrimagnetic that occur in the conditions considered here (H=0 and T>Tf or T⩾4.2 K and strong magnetic fields) and are discussed in connection with changes in the magnetic excitation spectrum caused by local breakdowns of collinear spin ordering and frustrations.