Monte Carlo analysis for finite temperature magnetism of Nd${}_2$Fe${}_{14}$B permanent magnet

Abstract

We investigate the effects of magnetic inhomogeneities and thermal fluctuations on the magnetic properties of a rare earth intermetallic compound, Nd${}_2$Fe${}_{14}$B. The constrained Monte Carlo method is applied to a Nd${}_2$Fe${}_{14}$B bulk system to realize the experimentally observed spin reorientation and magnetic anisotropy constants $K_m^{\mathrm{A}}(m=1,2,4)$ at finite temperatures. % Subsequently, it is found that the temperature dependence of $K_1^{\mathrm{A}}$ deviates from the Callen--Callen law, $K_1^{\mathrm{A}}(T)\propto M(T{)}^3$, even above room temperature, $T_{\mathrm{R}}\sim 300\mathrm{K}$, when the Fe (Nd) anisotropy terms are removed to leave only the Nd (Fe) anisotropy terms. This is because the exchange couplings between Nd moments and Fe spins are much smaller than those between Fe spins. % It is also found that the exponent $n$ in the external magnetic field $H_{\mathrm{ext}}$ response of barrier height ${\mathcal{F}}_{\mathrm{B}}={\mathcal{F}}_{\mathrm{B}}^0(1-H_{\mathrm{ext}}/H_0{)}^n$ is less than $2$ in the low-temperature region below $T_{\mathrm{R}}$, whereas $n$ approaches $2$ when $T>T_{\mathrm{R}}$, indicating the presence of Stoner--Wohlfarth-type magnetization rotation. This reflects the fact that the magnetic anisotropy is mainly governed by the $K_1^{\mathrm{A}}$ term in the $T>T_{\mathrm{R}}$ region.

arXiv comment10 pages, 14 figures

References in corpus (8)

• Constrained Monte Carlo Method and Calculation of the Temperature Dependence of Magnetic Anisotropy
• Microscopic origin of Heisenberg and non-Heisenberg exchange interactions in ferromagnetic bcc Fe
• Thermal activation in permanent magnets
• Extended Magnetic Exchange Interactions in the High-Temperature Ferromagnet MnBi
• Theoretical evaluation on the temperature dependence of magnetic anisotropy constants of Nd2Fe14B - Effects of exchange field and crystal field strength -
• Relevance of $4f$-$3d$ exchange to finite-temperature magnetism of rare-earth permanent magnets: an ab-initio-based spin model approach for NdFe${}_{12}$N
• General Formalism for Magnetic Anisotropy Constants
• Effects of spin fluctuation on the magnetic anisotropy constant of itinerant electron magnets

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