Quantum Theory of Rare-Earth Magnets

Abstract

Strong permanent magnets mainly consist of rare earths ($R$) and transition metals ($T$). The main phase of the neodymium magnet, which is the strongest magnet, is Nd${}_2$Fe${}_{14}$B. Sm${}_2$Fe${}_{17}$N${}_3$ is another magnet compound having excellent magnetic properties comparable to those of Nd${}_2$Fe${}_{14}$B. Their large saturation magnetization, strong magnetocrystalline anisotropy, and high Curie temperature originate from the interaction between the $T$-3d electrons and $R$-4f electrons. This article discusses the magnetism of rare-earth magnet compounds. The basic theory and first-principles calculation approaches for quantitative description of the magnetic properties are presented, together with applications to typical compounds such as Nd${}_2$Fe${}_{14}$B, Sm${}_2$Fe${}_{17}$N${}_3$, and the recently synthesized NdFe${}_{12}$N.

arXiv comment12 pages, 9 figures

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• Important descriptors and descriptor groups of Curie temperatures of rare-earth transition-metal binary alloys
• Intrinsically weak magnetic anisotropy of cerium in potential hard-magnetic intermetallics
• Prediction on Properties of Rare-earth 2-17-X Magnets Ce2Fe17-xCoxCN : A Combined Machine-learning and Ab-initio Study
• Data Assimilation Method for Experimental and First-Principles Data: Finite-Temperature Magnetization of (Nd,Pr,La,Ce)${}_2$(Fe,Co,Ni)${}_{14}$B
• Power law analysis for temperature dependence of magnetocrystalline anisotropy constants of Nd${}_2$Fe${}_{14}$B magnets
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• Predicting the Curie temperature of magnetic materials with automated calculations across chemistries and structures
• First-principles calculations of the magnetocrystalline anisotropy of the prototype 2:17 cell boundary phase Y(Co${}_{1-x-y}$Fe${}_x$Cu${}_y$)${}_5$
• Noncollinearity effects on magnetocrystalline anisotropy for $R_2$Fe${}_{14}$B magnets
• Resonant two-laser spin-state spectroscopy of a negatively charged quantum dot-microcavity system with a cold permanent magnet
• The effects of V doping on the intrinsic properties of SmFe10Co2 alloys: a theoretical investigation
• Analytic Expression for Magnetic Activation Energy
• Impact of Lattice Distortions on Magnetocrystalline Anisotropy and Magnetization in (Nd${}_{1-x}$Pr${}_x$)${}_2$Fe${}_{14}$B Alloys