Giant Magnetic Fluctuations at the Critical Endpoint in Insulating HoMnO3

TL;DR

This study uncovers a critical endpoint in insulating HoMnO3 characterized by giant magnetic fluctuations and divergent susceptibility, revealing critical phenomena in insulating magnets near CEPs.

Contribution

It reports the observation of a critical endpoint in an insulating magnet, highlighting critical fluctuations previously mainly studied in itinerant systems.

Findings

Emergent critical endpoint at 2.05 T and 2.2 K

Divergent magnetic susceptibility indicating strong critical fluctuations

Suppressed thermal conductivity near the CEP

Abstract

Although abundant research has focused recently on the quantum criticality of itinerant magnets, critical phenomena of insulating magnets in the vicinity of critical endpoints (CEP's) have rarely been revealed. Here we observe an emergent CEP at 2.05 T and 2.2 K with a suppressed thermal conductivity and concomitant strong critical fluctuations evident via a divergent magnetic susceptibility (e.g., chi''(2.05 T, 2.2 K)/chi''(3 T, 2.2 K)=23,500 %, comparable to the critical opalescence in water) in the hexagonal insulating antiferromagnet HoMnO3.