Magnetic properties of samples of the system Ga_xFe_1-x[NiCr]O₄with frustrated magnetic structure

Abstract

Magnetic properties of samples of the system GaxFe1 −x[NiCr]O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8) are investigated. The assumption is made that two magnetic phase transitions take place for the ferrites with x ≥ 0.2: at TC the transition from the paramagnetic state to a spin-glass state; and at Tt a second transition from a spin-glass state to a frustrated magnetic phase. This assumption is in good agreement with theoretical models. It is established that long-range magnetic ordering occurs at the temperature Tt. It is suggested that a frustrated magnetic structure in one sublattice is necessary for the occurrence of anomalous dependences of the spontaneous magnetization on temperature σs(T) of N, P or L type. It is established that if the frustrated magnetic structure is present in both sublattices of the ferrite, an anomalous σs(T) curve of another type is formed. Our conclusion is that the reason for the frustration of the magnetic connections in the samples of the system GaxFe1 −x[NiCr]O4 with x ≤ 0.2 is the presence of strong indirect interlattice interaction FeA3+ – O2− –Cr B3+ of positive sign.