Particle size dependent exchange bias and cluster-glass states in LaMn_0.7Fe_0.3O₃

Abstract

The cluster-glass compound LaMn0.7Fe0.3O3 was synthesized with average particle sizes ∼20, ∼90, and ∼300 nm. We observed a shift of the magnetic hysteresis loop in the field axis while the sample was cooled in an external magnetic field. The systematic shift of the hysteresis loops and the cooling field dependence of the shift indicated the phenomenon of exchange bias. The exchange bias field was found to be strongly dependent on the particle size, where the exchange bias field decreased considerably with an increase of particle size, and the weak effect of exchange bias was observed for particles with size ∼300 nm. A cluster-glass state with short range ferromagnetic clusters embedded in the spin-glass like host has been proposed, where the average size of the ferromagnetic cluster increases with particle size.