Preparation at moderate pressures, crystal and magnetic structure and magnetotransport of the ferrimagnetic CeCu3Mn4O12 perovskite

Abstract

Moderate-pressure conditions of 2 GPa has been used to stabilize the complex perovskite CeCu3Mn4O12. It can be considered as a derivative of the parent CaCu3Mn4O12 compound, by full replacement of Ca by Ce cations. The electronic injection leads to a very substantial increment of the ferromagnetic TC, up to 395 K. This material has been studied by x-ray diffraction and neutron powder diffraction (NPD) and magnetotransport measurements. It presents a ABO3 perovskite superstructure, where the A positions are occupied by Ce and Cu, ordered in a 1:3 arrangement giving rise to the body-centering of the unit cell. The crystal structure is cubic, space group Im 3¯ (no. 204), with a=7.30331(9) Å at room temperature. At the B positions, Mn adopts a mixed oxidation state of 3.65+ as demonstrated by a bond-valence study; MnO6 octahedra are considerably tilted by 19°, due to the relatively small size of the A-type cations. The magnetic structure, studied by NPD at 2 K, reveals that Mn and Cu spins are ordered below TC in an antiparallel arrangement. The refined magnetic moments at the Mn and Cu sublattices, of 1.92 and −0.3 μB/at., respectively, account for the observed saturation magnetization at 2 K, of 7μB/f.u.. A semiconducting behaviour is displayed between 10 and 400 K; a negative magnetoresistance (MR) of 18% is achieved at 5 K for H=4 T, and a substantial MR of 5% is attained at 300 K for H=9 T.