Noncollinearity effects on magnetocrystalline anisotropy for $R_2$Fe${}_{14}$B magnets

Abstract

We present a theoretical investigation of the magnetocrystalline anisotropy (MA) in $R_2$Fe${}_{14}$B ($R$ is a rare-earth element) magnets in consideration of the non-collinearity effect (NCE) between the $R$ and Fe magnetization directions. In particular, the temperature dependence of the MA of Dy${}_2$Fe${}_{14}$B magnets is detailed in terms of the $n$th-order MA constant (MAC) $K_n(T)$ at a temperature $T$. The features of this constant are as follows: $K_1(T)$ has a broad plateau in the low-temperature range and $K_2(T)$ persistently survives in the high-temperature range. The present theory explains these features in terms of the NCE on the MA by using numerical calculations for the entire temperature range, and further, by using a high-temperature expansion. The high-temperature expansion for $K_n(T)$ is expressed in the form of $K_n(T)={\kappa }_1(T)\left[1+\delta (T)\right][-\delta (T){]}^{n-1}$, where ${\kappa }_1(T)$ is the part without the NCE and $\delta (T)$ is a correction factor for the NCE introduced in this study. We also provide a convenient expression to evaluate $K_n(T)$, which can be determined only by a second-order crystalline electric field coefficient and an effective exchange field.

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References in corpus (7)

• Quantum Theory of Rare-Earth Magnets
• Monte Carlo analysis for finite temperature magnetism of Nd${}_2$Fe${}_{14}$B permanent magnet
• Realization of the thermal equilibrium in inhomogeneous magnetic systems by the Landau-Lifshitz-Gilbert equation with stochastic noise, and its dynamical aspects
• Anisotropy of exchange stiffness based on atomic-scale magnetic properties in rare-earth permanent magnet Nd${}_2$Fe${}_{14}$B
• Role of typical elements in Nd${}_2$Fe${}_{14}$$X$ ($X$ = B, C, N, O, F)
• Theoretical evaluation on the temperature dependence of magnetic anisotropy constants of Nd2Fe14B - Effects of exchange field and crystal field strength -
• Power law analysis for temperature dependence of magnetocrystalline anisotropy constants of Nd${}_2$Fe${}_{14}$B magnets

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