First principles band structure calculations for rare earth-transition metal compounds: magnetization, hyperfine parameters and magnetocrystalline anistropy

Abstract

First principles self-consistent band structure calculations using the augmented spherical wave method were used to calculate (i) the average and local magnetic moments in Y 2Fe 14B, Y 2Co 14B and in binary Y-Fe and Y-Co compounds, (ii) 57Fe-hyperfine parameters for Y 2Fe 14B and (iii) the A 0 2 crystal field parameters for R 2Fe 14B compounds (R = rare earth ). The effects of volume changes and of TM-B (TM = transition metal: Fe, Co) interactions on the magnetization are discussed. The calculated isomer shifts and quadrupole splittings for Y 2Fe 14B are in good agreement with experimental data, but the calculated hyperfine fields are systematically slightly too small. The crystal field parameters A 0 2 for the two R sites in R 2Fe 14B and related compounds have been calculated from the aspherical charge density of the valence electrons of the R atoms themselves. The results are in good agreement with experiment. We propose a simple model, based on Miedema's “macroscopic atom” model for cohesion in metals, from which trends in the magnetocrystalline anisotropy can be understood qualitatively.