Homogeneity range, crystal structure and magnetic properties of the ThMn12-type compounds Gd1-nNdn(Fe,Mo)12 (n=0-1.0)

The existence range, crystal structure and magnetic properties of the Gd1-nNdn(Fe,Mo)(12) compound series (n=0-1) have been studied by electron probe X-ray microanalysis, X-ray diffraction followed by Rietveld refinement, and magnetization measurements. It has been found that the tetragonal ThMn12-type structure is formed for Mo concentrations from 8.7 to 28.7 at.% (n=0) and from 6.4 to 23.4 at.% (n=1.0). The concentration of molybdenum at the borders of the homogeneity range linearly decreases with it. The structure evolution of Gd1-nNdn(Fe,Mo)(12) upon substitution of Nd for Gd is determined by two competitive factors: the lanthanide contraction with increasing atomic number and the charge transfer effect, so that the ratio of the unit cell parameters cia decreases. The saturation magnetization of Gd1-nNdn(Fe,Mo)(12) with an average Mo content of 19.1+/-0.7 at.% increases with it, the Curie temperature being about 25 K higher between n approximate to0.2 and n approximate to0.8 compared to the values for n=0 and n=1. At the same time, the Curie temperature at the Fe-rich border of homogeneity range continuously decreases with increasing Nd concentration. (C) 2001 Elsevier Science B.V. All rights reserved.