Chemical size effect on the magnetic and electrical properties in the (Tb_1-xEu_x)MnO₃ (0 ≤ x ≤ 1.0) system

The effect of isovalent chemical substitution of Eu³⁺ into the Tb³⁺ sites on the magnetic and electrical properties of (Tb _1-xEu_x)MnO₃ (0 ≤ x ≤ 1.0) system has been investigated. The orthorhombic structure with space group Pbnm is observed in this series of materials. An increase in Mn-O bond distance with increasing Eu content leads to improvement in the overlap between the Mn 3d and O 2p orbital thereby causing a decrease in activation energy and resistivity. Moreover, as the Eu content increases, the effective moments (μ_eff) are reduced linearly and an exchange coupling is observed in Tb-Tb, Tb-Eu, and Eu-Eu complexes for x = 0.1 and 0.3 samples. Both these features can be related to the substitution of bigger Eu³⁺ ions replacing the original Tb-Tb coupling.