Relation Between Magnetism and Metal-Insulator Transition in Mn-DOPED SrRuO3

Neutron powder diffraction experiments were carried out on the insulating phase of the mixed compounds SrRu_1-xMn_xO₃ for 0.4 ≤ x ≤ 0.6. We have found that the ferromagnetic phase observed at x ~ 0 changes into the C-type antiferromagnetic phase above x ≥ 0.4. In addition, this transition accompanies the structural variation from orthorhombic phase (x ~ 0) to tetragonal phase (x ≥ 0.4). With increasing x, the AF moment is strongly enhanced from 1.1 μB (x = 0.4) to 2.6 μB (x = 0.6), which is tightly coupled with the elongation of the tetragonal c/a ratio. We suggest from the experimental results that the evolution of the AF order in the insulating phase is generated by the superexchange interaction originating in the strong electronic correlation between the d electrons on Ru and Mn ions.