Universality of the magnetization irreversibility curve of systems with competing interactions (manganites, cobaltites, ferrites)

Abstract

Experimental data on the temperature dependences of the magnetization of manganites, cobaltites, and ferrites are analyzed. Their common feature is magnetization irreversibility: below a temperature T* for a fixed field strength, the magnetization is different for cooling in a field (MFC) and in zero field (MZFC). It is shown that the T*(H) curve is universal for all the dispersed oxides (nanocompound, nanopowder) and is consistent with the theoretical Almeida-Thouless curve (T* ∼ H2/3) over the entire range of magnetic fields. In the case of monolithic samples (single crystals, ceramics), in strong magnetic fields there is a transition to a quadratic dependence T* ∼ H2 in agreement with the Gabay-Toulousse theory. This phenomenon is interpreted in terms of spin-glass polyamorphism.