Structural and magnetic properties of RFe9Si2Cx compounds (R = Ce, Pr, Nd, Sm; x = 0.5, 1.0, 1.5)

A systematic investigation of crystallographic and intrinsic magnetic properties of the compounds RFe9Si2Cx (R = Ce, Pr, Nd, Sm; x = 0.5, 1.0, 1.5) has been carried out. The lattice parameters a, c and the unit cell volumes increase with increasing C contents, resulting in the increases of Curie temperatures by about 100-150 K between x = 0.5 and x = 1.5. The saturation magnetization of RFe9Si2Cx (R = Pr, Nd, Sm) at 1.5 K passes through a maximum at x = 1.0, and then decreases slightly. Meanwhile, the average iron moment mu (Fe) at 1.5 K is 1.57 mu (B) for x = 1.0 and 1.63 mu (B) for x = 1.5 in CeFe9Si2Cx compounds. SmFe9Si2Cx compounds have uniaxial anisotropy with the anisotropy fields H-A estimated around 132 kOe at 1.5 K and 50 kOe at 300 K (x = 1.5), respectively. First-order magnetization processes are observed in the NdFe9Si2Cx compounds and the first-order magnetization processes critical field H-cr is found to increase with x. In addition, the critical temperature for the onset of the first-order magnetization processes transition is around 90 K in the case of x = 1.0. (C) 2001 American Institute of Physics.Physics, AppliedSCI(E)EI9ARTICLE52852-28568