Impact of Lattice Distortions on Magnetocrystalline Anisotropy and Magnetization in (Nd${}_{1-x}$Pr${}_x$)${}_2$Fe${}_{14}$B Alloys

Abstract

Nd${}_2$Fe${}_{14}$B -- a widely used permanent magnet -- has magnetocrystalline anisotropy constants that differ between the bulk and interface regions. This study explores the effects of lattice distortion on the magnetocrystalline anisotropy ($K_{\mathrm{u}}$) and magnetization of (Nd${}_{1-x}$Pr${}_x$)${}_2$Fe${}_{14}$B. Nd${}_2$Fe${}_{14}$B alloys were fabricated; scanning transmission electron microscopy revealed a compressive strain of up to 25% near grain boundaries. Using the full-potential Korringa--Kohn--Rostoker method, we calculated the strain dependence of $K_{\mathrm{u}}$, showing that although $K_{\mathrm{u}}$ is 4.2 MJ/m${}^3$ under strain-free conditions at 0 K, it becomes negative in regions with 25% compressive strain. Additionally, Pr${}_2$Fe${}_{14}$B exhibits a larger $K_{\mathrm{u}}$ than Pr${}_2$Fe${}_{14}$B under undistorted conditions, whereas Pr-rich alloys exhibit a more pronounced reduction in $K_{\mathrm{u}}$ under strain. These findings highlight the critical influence of lattice distortions on magnetic properties. The calculated strain-dependent magnetic anisotropy parameters provide valuable inputs for future micromagnetic simulations, aiding the design of advanced magnetic materials.

11 pages, 8 figures, includes experimental and first-principles calculations

References in corpus (2)

• Quantum Theory of Rare-Earth Magnets
• Effects of trace elements on the crystal field parameters of Nd ions at the surface of Nd${}_2$Fe${}_{14}$B grains