Observation of Spontaneous Magnetization in the Layered Perovskite Ferromagnet, (p-Chloroanilinium)2CuBr4

Abstract

The crystal structure and magnetic properties of the layered perovskite, (p-chloroanilinium)₂CuBr₄ (1) have been investigated. The crystal of 1 belongs to the orthorhombic Pbca space group [a = 7.551(2) Å, b = 32.082(10) Å, c = 7.879(2) Å, and Z = 4], which is typical of the material family. The temperature dependence of the ac susceptibility (χ_ac = (∂M/∂H)) of a polycrystalline sample shows magnetic ordering at 15 K with an abrupt increase of the value. In the ordered state, the field dependence of χ_ac, namely the differential susceptibility, and the dc magnetization indicate a hysteresis loop of the magnetization, which can be ascribed to the presence of spontaneous magnetization. Furthermore, single-crystal magnetic measurements indicate that the magnetic properties of 1 are quite anisotropic. When the field is along the b axis (perpendicular to the inorganic layer), the field dependence of χ_ac shows the hysteresis behavior, as observed for the polycrystals, but when it is parallel to the a axis (parallel to the layer), χ_ac shows metamagnetic transitions. The observed anisotropy can be understood in terms of a magnetic easy axis parallel to the a axis, an antiferromagnetic interlayer interaction, and a spin canting which produces spontaneous magnetization along the b axis.