Influence of Ga doping on rare earth moment ordering and ferromagnetic transition in Nd0.7Sr0.3Co1−xGaxO3

Abstract

We report the impact of dilution of Co sublattice by non-magnetic Ga3+ ion on the magnetic, electrical, and magnetoresistive properties in Nd0.7Sr0.3Co1−xGaxO3 for x = 0–0.12. Field-cooled magnetization of the parent compound (x = 0) shows an anomalous maximum at T* = 54.6 K much below the onset of ferromagnetic transition (TC = 160 K) of the Co sublattice, which is attributed to the polarization of Nd-4f moments antiparallel to the Co-3d sublattice. Both TC and T* shift to low temperature with increasing x and the Nd-4f spin reverses from antiparallel to parallel with increasing strength of the magnetic field. While the value of high field magnetization is not seriously affected by Ga doping, coercive field at 10 K increases dramatically with increasing x. Ga substitution transforms ferromagnetic metallic state into ferromagnetic insulating state for x ≥ 0.03 and decreases the magnitude of magnetoresistance from 6% for x = 0% to 0.5% for x = 0.12.