Seminars

Title: Computational materials modelling of rare earth magnets – from skyrmions to commercial permanent magnets.
 
Abstract: In this talk modelling the interactions between the magnetic moments in rare earth (R) magnets is described, focussing on the role of the valence electrons and topology of their electronic structure. Case studies of skyrmion lattices in centrosymmetric Gd intermetallics (1) and incommensurate magnetic order in the Weyl semimetals RAlSi (2) are highlighted.  A quantitative model is presented for rare earth - transition metal magnets, inspired by the ‘standard model’ and demonstrated for the extensively used strong magnet, Nd₂Fe₁₄B. A rich and complex behaviour originating from the Fe atoms, is revealed which is often missed out currently from larger-scale simulations (3). Real magnets always contain defects, and these are understood to adversely affect the coercivity, one of the most sought-after properties of commercial magnets. Current state-of- the-art models either assume pristine materials or treat defects heuristically, which limits their predictive power. This talk introduces a simple but accurate analytical model of defects (4), with parameters determined from first-principles calculations, suitable for deployment in large-scale atomistic spin dynamics calculations and statistical analyses.  Point defects, in the form of Ti atom substitutions, are shown to modify dramatically the magneto-crystalline anisotropy of the archetypal “rare earth-lean” magnet SmFe₁₁Ti.

1. J. Bouaziz et al. Phys. Rev. Lett.128, 157206, (2022); (2) J. Bouaziz et al. Phys. Rev.B 109, L201108, (2024); (3) J. Bouaziz, C. E. Patrick and J. B. Staunton, Physical Review B107, L020401, (2023); (4) C. E. Patrick et al., Phys. Rev. Lett. 132, 056703, (2024) (Editor’s Suggestion).