Study of structural and magnetic properties and exchange interactions in (Y1-xGdx)(3)Fe27.5Ti1.5 [X=0, 0.2, 0.5, 0.8, 1.0]

The alloys (Y-1-Gd-x(x))(3)Fe27.5Ti1.5 [x = 0, 0.2, 0.5, 0.8, 1.01] were pr epared and structurally characterized by the Rietveld analysis of powder X- ray diffraction patterns. The saturation magnetization at 5 K as well as at 300 K monotonically decreased with increasing Gd concentration, due to the antiferromagnetic ordering between the Gd and Fe magnetic moments. The Cur ie temperature increased from 386 K for x = 0 to 525 K for x = 1.0. The mol ecular field coefficients for different exchange interactions were estimate d from the mean field analysis of the Curie temperatures of Y3Fe27.5Ti1.5 a nd Gd3Fe27.5Ti1.5 From these coefficients, the Curie temperatures calculate d for the intermediate concentrations were found to agree with the observed values. A Wigner-Seitz cell approach has been employed for the analysis of Fe-57 Mossbauer spectra. The average hyperfine fields at 30 and 300 K incr eased with increase of Gd concentration. The Fe sublattice anisotropy, dete rmined from the XRD of magnetically aligned samples, has planar nature. (C) 1999 Elsevier Science Ltd. All rights reserved.