Structural and magnetic properties of Pr(Fe, Si)11Cx compounds (0.5 ≤ x ≤ 1.5)

Abstract

Three samples of nominal compositions PrFe9Si2Cx (x=0.5, 1.0, 1.5) were prepared by arc-melting. The crystallographic structure and the magnetic properties of the obtained compounds were investigated by means of X-ray and neutron powder diffraction and magnetic measurements. They crystallize within a filled variant of the tetragonal BaCd11-type structure, with Pr in the 4(a) position, Fe in the 4(b), 32(i) and 8(d) sites, Si atoms being located in the remaining part of 8(d) sites. Carbon atoms occupy 8(c) octahedral sites surrounded by four Fe and two Pr atoms. From the neutron diffraction study, the composition of the three obtained compounds is found to be close to PrFe10SiCx, but the occupancy of the Fe atoms in the 8(d) sites decreases for high carbon contents. The Curie temperature increases from 331 (1) to 476 (1)K for x∼0.5 and 1.5, respectively, and the saturation magnetization at 4K reaches its maximal value for x∼1.0 (Ms=18.21μB/f.u.). From the neutron diffraction data, a significant difference in the Fe moment amplitudes is observed between the 32(i) (μFe∼1.5μB) and the 4(b) and 8(d) sites (μFe∼2.5μB). The easy magnetization axis lies within the (001) plane.