The crystallographic and magnetic properties of RFe9Si2Cx (R = Ce, Nd; x = 0.5, 1.0, 1.5) with BaCd11-type structure are studied. The structure is tetragonal, belonging to the space group I4(1)/amd with Nd in 4a site, Fe in 4b, 32i and half of 8d sites, Si in the left half of 8d site, and C in 8c site. The first-order magnetization process (FOMP) transition occurred in NdFe9Si2Cx (x = 0.5, 1.0, 1.5) at low temperature. The critical field increases with the carbon content, and decreases with the increase in temperature. The magnetization curves of Nd(Fe,Si)(11)C-x are calculated to simulate the FOMP. The calculated curves indicate a type-I FOMP transition. In addition, the crystal-field coefficients A(nm) are calculated by point charge model, and the molecular field coefficients n(RFe) and n(FeFe) are obtained based on the molecular-field model. (C) 2001 Elsevier Science Ltd. All rights reserved. References: 13
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