Chemical pressure effects on Tm_1-yR_yMn_0.3Co_0.7O_{3 due to element substitution at A-site}

To clarify the chemical pressure effects on TmMn0.3Co0.7O3 due to element substitution at an A-site, the crystal structure and magnetic properties of Tm1-yRyMn0.3Co0.7O3 (R = Y and Lu) were investigated. All the prepared samples possessed a perovskite-type orthorhombic structure with the Pnma space group, and the unit-cell volume V increased with the average radius of A-site ions rR. From the effective magnetic moment Peff and M-H measurements, it was found that the electronic states of the ions in the samples were Tm3+, Mn4+, Co2+(highspin state, S = 3/2), and Co3+(low-spin state, S = 0). The physical parameters including the canted antiferromagnetic transition temperature Tc increased with V. The field-cooled magnetization MFC below 30 K could be explained by the antiferromagnetic interaction between the paramagnetic Tm and the 3d metal sublattices. Since Tc and the fitting parameter of this two-sublattice model increased with V, these changes were considered to be attributed to the chemical pressure generated by element substitution at the A-site.