Study of structural and magnetic properties and exchange interactions in (Y<inf>1-x</inf>Gd<inf>x</inf>)<inf>3</inf>Fe<inf>27.5</inf>Ti<inf>1.5</inf> [x = 0, 0.2, 0.5, 0.8, 1.0]

The alloys (Y1-xGdx)3Fe27.5Ti1.5 [x = 0, 0.2, 0.5, 0.8, 1.0] were prepared 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 Curie temperature increased from 386 K for x = 0 to 525 K for x = 1.0. The molecular field coefficients for different exchange interactions were estimated from the mean field analysis of the Curie temperatures of Y3Fe2.75Ti1.5 and Gd3Fe27.5Ti1.5. From these coefficients, the Curie temperatures calculated for the intermediate concentrations were found to agree with the observed values. A Wigner-Seitz cell approach has been employed for the analysis of 57Fe Moessbauer spectra. The average hyperfine fields at 30 and 300 K increased with increase of Gd concentration. The Fe sublattice anisotropy, determined from the XRD of magnetically aligned samples, has planar nature.