Exchange bias driven by the structural/magnetic transition in Mn-doped SrRuO3

Abstract

Magnetic properties of bulk polycrystalline Mn-doped SrRu1−xMnxO3 perovskite, at doping range 0.2≤x≤0.3, were studied by both magnetization and ac-susceptibility measurements. It was found that the exchange bias (EB) effect emerges with increasing Mn doping in SrRu1−xMnxO3 at x≈0.25, following the ferromagnetic (FM) to antiferromagnetic (AFM) phase transition. This transition is accompanied with the change in structure symmetry and then the EB field, HEB, increases significantly in doping range 0.25<x≤0.3. The EB effect was verified by both cooling magnetic field, Hcool, dependence of the HEB and training effect. A markedly nonmonotonic HEB vs. Hcool dependence with maximum at around 40kOe was found, resembling the behavior of phase-separated EB systems. Moreover, a clear analogy with behavior of classic EB system of Pr1/3Ca2/3MnO3 was noticed, strongly suggesting that the EB effect in SrRu1−xMnxO3 originates from exchange interactions at the interface of nanoscale FM clusters (size of ~1.6nm at x=0.3) coexisting together with dominant AFM phase at the boundary of the first-order FM/AFM transition. The training effect observed is well understandable within the spin-configuration relaxation model and indicates important contribution to the EB behavior from the AFM domains rearrangement at the interface.