Enhanced magnetic moment in ErMnO₃ by copper doping and negative magnetocapacitance effect

Single phase ErCu_xMn_1-xO₃(0 ≤ x ≤ 0.1) compounds were prepared by the standard solid-state reaction. The doping effects on the crystal structure, magnetic properties and dielectric properties were systematically studied. X-ray diffraction patterns show that all samples are single phase and crystallized in a hexagonal structure belonging to the P6₃cm space group. Rietveld refinement indicates that the α lattice parameter increases and the c lattice parameter decreases with increasing Cu concentration. The magnetic moments of the doped samples are enhanced, which is due to modification of the frustrated spin arrangement by the superexchange interaction between Cu²⁺ ions and Mn³⁺ ions. The specific heat capacity data show a peak at the antiferromagnetic transition temperature, which decreases from 77 K for x = 0 to 61K for x = 0.1. The samples become more conductive upon doping, which is responsible for the increase in the dielectric constant. A large negative magnetocapacitance effect was observed in paramagnetic-state ErCu_0.05Mn_0.95O ₃ at 300 K.