Critical-Element-Free Permanent-Magnet Materials Based on Ce2Fe14B

Abstract

Developing a critical-element-free low-cost permanent magnet is an urgent necessity in view of rapidly developing technologies and the associated huge market demand for ${\mathrm{Nd}}_{2}{\mathrm{Fe}}_{14}\mathrm{B}$-based magnets. Here, inspired by the abundant and low-cost nature of $\mathrm{Ce}$ and these high-performance ${\mathrm{Nd}}_{2}{\mathrm{Fe}}_{14}\mathrm{B}$ permanent magnets, we explore whether it is in fact possible to attain a useful performance in alloys based on the sister material ${\mathrm{Ce}}_{2}{\mathrm{Fe}}_{14}\mathrm{B}$, employing both experimental and theoretical efforts. Experimentally, we study ${\mathrm{Ce}}_{2}{\mathrm{Fe}}_{14}\mathrm{B}$ with $\mathrm{Co}$, $\mathrm{La},$ and $\mathrm{Zr}$ substitutions. The $\mathrm{Zr}$ substitution is explored in view of $\mathrm{Zr}$'s frequent role in enhancing magnetic anisotropy in permanent magnets, while the $\mathrm{Co}$ and $\mathrm{La}$ substitutions serve to remedy the too-low Curie point of 433 K in the base alloy. While we find no $\mathrm{Zr}$-related anisotropy enhancement either experimentally or theoretically, the cosubstitution of $\mathrm{La}$ and $\mathrm{Co}$ indeed improves the Curie temperature as well as the magnetization, ${M}_{s}$, with a potential energy product as high as 38 MG Oe. These properties together suggest optimization of the alloy ${\mathrm{La}\mathrm{Ce}\mathrm{Fe}}_{12.7}{\mathrm{Co}}_{1.3}\mathrm{B}$ (with only 7 wt % cobalt) as a critical-element-free permanent magnet. While the substituted elements do not enhance magnetic anisotropy, from theory, we find a substantial increase, to a first anisotropy constant, ${K}_{1}$, as high as 4.24 $\mathrm{MJ}/{\mathrm{m}}^{3}$, associated with $\mathrm{Bi}$ substitution for $\mathrm{Ce}$. Our experimental and theoretical results demonstrate the great potential of $\mathrm{La}$, $\mathrm{Co},$ and $\mathrm{Bi}$ substitutions in developing low-cost and critical-element-free ${\mathrm{Ce}}_{2}{\mathrm{Fe}}_{14}\mathrm{B}$-based permanent magnets.