Hydrostatic pressure effect on Co-based honeycomb magnet BaCo2(AsO4)2

TL;DR

This study investigates how hydrostatic pressure influences the magnetic phase transitions and critical fields of the honeycomb antiferromagnet BaCo2(AsO4)2, revealing pressure-dependent stabilization of magnetic states and implications for Kitaev physics.

Contribution

It provides the first detailed analysis of hydrostatic pressure effects on transition temperatures and critical fields in BaCo2(AsO4)2, informing magnetic models of this material.

Findings

Magnetic ordering temperature increases marginally with pressure.

Critical fields H1 and H2 change significantly under pressure.

H1 increases, stabilizing the antiferromagnetic state, while H2 decreases, affecting the Kitaev spin liquid hypothesis.

Abstract

The honeycomb antiferromagnet BaCo2(AsO4)2, in which small in-plane magnetic fields (H1 = 0.26 T and H2 = 0.52 T at T = 1.8 K < TN = 5.4 K) induce two magnetic phase transitions, has attracted attention as a possible candidate material for the realization of Kitaev physics based on the 3d element Co2+. Here, we report on the change of the transition temperature TN and the critical fields H1 and H2 of BaCo2(AsO4)2 with hydrostatic pressure up to ~ 20 kbar, as determined from magnetization and specific heat measurements. Within this pressure range, a marginal increase of the magnetic ordering temperature is observed. At the same time, the critical fields are changed significantly (up to ~ 25-35 %). Specifically, we find that H1 is increased with hydrostatic pressure, i.e., the antiferromagnetic state is stabilized with hydrostatic pressure, whereas H2, which was previously associated with a transition into a proposed Kitaev spin liquid state, decreases with increasing pressure. These results put constraints on the magnetic models that are used to describe the low-temperature magnetic properties of BaCo2(AsO4)2.