Anisotropy at twin interfaces in $R{T}_{12}$ ($R$=rare earth, $T$=transition metal) magnets

Abstract

RT\textsubscript{12} materials continue to attract attention due to their potential use as ``rare-earth-lean'' permanent magnets, but converting their promising intrinsic properties into practical high performance remains an elusive goal. Sophisticated experimental characterization techniques are providing unprecedented insight into the structure of these materials at the atomistic scale. Atomistic spin dynamics or micromagnetics simulations could help unravel the links between these structures and resultant magnet performance, but require input data describing the intrinsic magnetic properties. Here, first-principles calculations based on density-functional theory are used to determine these properties for two model interface structures which have been derived from recently reported high resolution electron microscopy images. One model structure is a stoichiometric twin formed by mirroring the RT\textsubscript{12} structure in the (101) plane, and the other model structure is a ``stacking fault'' involving the insertion of a RT\textsubscript{4} plane and a displacement along the [100] axis. Magnetic moments and crystal field coefficients have been calculated for the optimized structures. The interfaces modify the magnetic properties at the sub-nm scale. In particular, in the R-rich region of the ``stacking fault'', the local easy axis of magnetization rotates by $49^{\circ }$ from its bulk direction, which may lead to reduced coercivity through the easier nucleation of reverse domains.

arXiv comment11 pages, 8 figures

References in corpus (16)

• Self-interaction correction in multiple scattering theory
• Micromagnetics of rare-earth efficient permanent magnets
• Crystal field splittings in rare earth-based hard magnets: an ab initio approach
• Effect of $R$-site substitution and the pressure on stability of $R$Fe${}_{12}$: A first-principles study
• Nitrogen as the best interstitial dopant among $X$=B, C, N, O and F for strong permanent magnet NdFe${}_{11}$Ti$X$: First-principles study
• Calculating temperature-dependent properties of Nd${}_2$Fe${}_{14}$B permanent magnets by atomistic spin model simulations
• (Sm,Zr)Fe${}_{12-x}$M${}_x$ (M=Zr,Ti,Co) for permanent-magnet applications: Ab initio material design integrated with experimental characterization
• Rare-earth/transition-metal magnets at finite temperature: Self-interaction-corrected relativistic density functional theory in the disordered local moment picture
• Anisotropy of exchange stiffness based on atomic-scale magnetic properties in rare-earth permanent magnet Nd${}_2$Fe${}_{14}$B
• On the limits of coercivity in permanent magnets
• High-order crystal field and rare-earth magnetism in RECo5 intermetallics
• Crucial role of Fe in determining the hard magnetic properties of Nd${}_2$Fe${}_{14}$B
• First-principles study on interface magnetic structure in Nd${}_2$Fe${}_{14}$B/(Fe,Co) exchange spring magnets
• The effect of the surface magnetic anisotropy of the neodymium atoms on the coercivity in the neodymium permanent magnet
• Effect of Element Doping and Substitution on the Electronic Structure and Macroscopic Magnetic Properties of SmFe${}_{12}$-based Compounds
• Crystal field coefficients for yttrium analogues of rare-earth/transition-metal magnets using density-functional theory in the projector-augmented wave formalism