Monoclinic YFe$_{12}$ phases predicted from first principles

TL;DR

This study predicts new monoclinic YFe12 phases with enhanced magnetic properties using first-principles calculations, showing increased magnetization and Curie temperature compared to the well-known ThMn12 structure.

Contribution

The paper introduces two novel monoclinic YFe12 structures with improved magnetic properties, identified through crystal structure prediction and first-principles calculations.

Findings

Increased magnetization from 25.6 to 26.8 μB/f.u.

Curie temperature raised from 792 K to 940 K.

Enhanced magnetic properties in Y(Fe$_{1-x}$Co$_{x}$)$_{12}$ systems.

Abstract

We searched for stable crystal structures of YFe$_{12}$ using a crystal structure prediction technique based on a genetic algorithm and first-principles calculations. We obtained two monoclinic $C2/m$ structures as metastable phases that are different from the well-known ThMn$_{12}$ structure. These two phases have advantages in their magnetism over the ThMn$_{12}$ structure: The total magnetization $M$ is increased from 25.6 $\mu_{\text{B}}$/f.u. up to 26.8 $\mu_{\text{B}}$/f.u. by the transformations. We also calculated Curie temperature $T_{\text{C}}$ for these structures within the mean-field approximation and predicted the increase of $T_{\text{C}}$ from 792 K up to 940 K, which is mainly caused by the increase of intersite magnetic couplings within the distance of 2.3--3.1\r{A}. The similar enhancements of $M$ and $T_{\text{C}}$ are also obtained in the pseudo-binary system Y(Fe$_{1-x}$Co$_{x}$)$_{12}$ with $x$ of 0--0.7.