The first-order magnetization process (FOMP) in NdFe9Si2Cx (x=0.5,1.0,1.5)

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 I41/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)11Cx are calculated to simulate the FOMP. The calculated curves indicate a type-I FOMP transition. In addition, the crystal-field coefficients Anm are calculated by point charge model, and the molecular field coefficients nRFe and nFeFe are obtained based on the molecular-field model.