Thermodynamic insights into the intricate magnetic phase diagram of EuAl$_{4}$

TL;DR

This study provides a comprehensive magnetic phase diagram of EuAl$_{4}$ under a c-axis magnetic field, revealing seven phases including a new high-field phase potentially related to skyrmions, advancing understanding of its magnetic properties.

Contribution

The paper offers the first detailed magnetic phase diagram of EuAl$_{4}$ under c-axis magnetic field, identifying a new high-field phase and elucidating complex magnetic interactions.

Findings

Seven magnetic phases mapped under c-axis magnetic field.

Identification of a new high-field phase, phase VII.

Evidence supporting the potential skyrmion phase region.

Abstract

The tetragonal intermetallic compound EuAl$_{4}$ hosts an exciting variety of low temperature phases. In addition to a charge density wave below 140 K, four ordered magnetic phases are observed below 15.4 K. Recently, a skyrmion phase was proposed based on Hall effect measurements under a $c$-axis magnetic field. We present a detailed investigation of the phase transitions in EuAl$_{4}$ under $c$-axis magnetic field. Our dilatometry, heat capacity, DC magnetometry, AC magnetic susceptibility, and resonant ultrasound spectroscopy measurements reveal three magnetic phase transitions not previously reported. We discuss what our results reveal about the character of the magnetic phases. Our first key result is a detailed $H \parallel [001]$ magnetic phase diagram mapping the seven phases we observe. Second, we identify a new high-field phase, phase VII, which directly corresponds to the region were skyrmions have been suggested. Our results provide guidance for future studies exploring the complex magnetic interactions and spin structures in EuAl$_{4}$.