Antiferromagnetism and phase transitions in non-centrosymmetric UIrSi$_3$

TL;DR

This study investigates the antiferromagnetic properties and phase transitions of UIrSi3, revealing complex magnetic behavior, phase transition characteristics, and underlying electronic structure through combined experimental and theoretical approaches.

Contribution

It provides a comprehensive analysis of the magnetic phase diagram and electronic structure of UIrSi3, highlighting the interplay of ferromagnetic and antiferromagnetic interactions in a non-centrosymmetric compound.

Findings

Antiferromagnetic order below 41.7 K with Ising-like behavior.

Identification of a tricritical point at 28 K and 5.8 T.

Electronic structure calculations support experimental magnetic properties.

Abstract

Magnetization and specific heat measurements on a UIrSi3 single crystal reveal Ising-like antiferromagnetism below T$_N$ = 41.7 K with easy magnetization direction along the c-axis of tetragonal structure. The antiferromagentic ordering is suppressed by magnetic fields > H$_c$ ({\mu}$_0$H$_c$ = 7.3 T at 2 K) applied along the c-axis. The first-order metamagnetic transition at H$_c$ exhibits asymmetric hysteresis reflecting a slow reentry of the complex ground-state antiferromagnetic structure with decreasing field. The hysteresis narrows with increasing temperature and vanishes at 28 K. A second-order metamagnetic transition is observed at higher temperatures. The point of change of the order of transition in the established H-T magnetic phase diagram is considered as the tricritical point (at T$_{tc}$ = 28 K and {\mu}$_0$H$_{tc}$ = 5.8 T). The modified-Curie-Weiss-law fits of temperature dependence of the a- and c-axis susceptibility provide opposite signs of Weiss temperatures, {\Theta}$_p^a$ ~ -51 K and {\Theta}$_p^c$ ~ +38 K, respectively. This result and the small value of {\mu}$_0$H$_c$ contrasting to the high T$_N$ indicate competing ferromagnetic and antiferromagnetic interactions responsible for the complex antiferromagnetic ground state. The simultaneous electronic-structure calculations focused on the total energy of ferromagentic and various antiferromagnetic states, the U magnetic moment and magnetocrystalline anisotropy provide results consistent with experimental findings and the suggested physical picture of the system.