Field-induced crossover from cluster-glass to ferromagnetic state in La₀.₇Sr₀.₃Mn₀.₇Co₀.₃O₃

Abstract

The thermodynamics and kinetics of the magnetic states of the semiconductor-like compound La₀.₇Sr₀.₃Mn₀.₇Co₀.₃O₃were studied by detailed magnetic measurements. The spontaneous magnetic state was found to be a cluster-glass phase which can cross over to a ferromagnetic state under an external magnetic field H. The defreezing temperature T[sub f] for the cluster-glass phase and the merging temperature T[sub m] for zero field cooled and field cooled magnetizations are related to the field H by H[sub j]=H[sub 0j](1-T[sub j]/T[sub c])[sup nj], where H[sub 0j] and n[sub j] are constants and j=f,m. Codoping tends to destroy the double exchange in Mn⁴⁺–O–Mn³⁺ and broadens the coexistence region of the cluster-glass and ferromagnetic states. The magnetic relaxation was found to deviate from the usual logarithmic time dependence and follow a power law.