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

Magnetic properties of bulk polycrystalline Mn-doped SrRu_1-xMn_xO₃ 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 SrRu_1-xMn_xO₃ 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, H_EB, increases significantly in doping range 0.25<x≤0.3. The EB effect was verified by both cooling magnetic field, H_cool, dependence of the H_EB and training effect. A markedly nonmonotonic H_EB vs. H_cool dependence with maximum at around 40 kOe was found, resembling the behavior of phase-separated EB systems. Moreover, a clear analogy with behavior of classic EB system of Pr_1/3Ca_2/3MnO₃ was noticed, strongly suggesting that the EB effect in SrRu_1-xMn_xO₃ originates from exchange interactions at the interface of nanoscale FM clusters (size of ∼1.6 nm 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.