Evolutionary search for cobalt-rich compounds in the yttrium-cobalt-boron system

TL;DR

This study uses evolutionary algorithms and first-principles calculations to discover and analyze cobalt-rich compounds in the Y-Co-B system, revealing new stable and metastable phases with enhanced magnetic properties at elevated temperatures.

Contribution

It introduces an evolutionary search approach to identify new cobalt-rich compounds in the Y-Co-B system and assesses their stability and magnetic properties.

Findings

37 cobalt-rich compounds predicted with high stability probability

YCo₁₆ and YCo₂₀ are metastable but stabilized at higher temperatures

Magnetization and Curie temperature are significantly higher than Y₂Co₁₇

Abstract

Modern high-performance permanent magnets are made from alloys of rare earth and transition metal elements, and large magnetization is achieved in the alloys with high concentration of transition metals. We applied evolutionary search scheme based on first-principles calculations to the Y-Co-B system and predicted 37 cobalt-rich compounds with high probability of being stable. Focusing on remarkably cobalt-rich compounds, YCo$_{16}$ and YCo$_{20}$, we found that, although they are metastable phases, the phase stability is increased with increase of temperature due to the contribution of vibrational entropy. The magnetization and Curie temperature are higher by 0.22 T and 204 K in YCo$_{16}$ and by 0.29 T and 204 K in YCo$_{20}$ than those of Y$_{2}$Co$_{17}$ which has been well studied as strong magnetic compounds.