Study of structural and magnetic properties and exchange interactions in (Y 1− xGd x) 3Fe 27.5Ti 1.5 [ x=0, 0.2, 0.5, 0.8, 1.0

Abstract

The alloys (Y 1− x Gd x ) 3Fe 27.5Ti 1.5 [ 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 Y 3Fe 27.5Ti 1.5 and Gd 3Fe 27.5Ti 1.5. 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 Mössbauer 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.