First order phase transition in the frustrated triangular antiferromagnet CsNiCl3

TL;DR

This study uses ultrasonic velocity measurements to investigate magnetic phase transitions in CsNiCl3, revealing that the 120-degree transition is weakly first order, challenging previous theories about chiral systems.

Contribution

It provides the first experimental evidence that the 120-degree phase transition in CsNiCl3 is weakly first order, contradicting the idea of new universality classes for chiral systems.

Findings

The 120-degree phase transition shows step-like variation in elastic constant C44.

Hysteresis effects indicate a weakly first order transition.

Results challenge the notion of new universality classes for chiral magnetic systems.

Abstract

By means of high-resolution ultrasonic velocity measurements, as a function of temperature and magnetic field, the nature of the different low temperatures magnetic phase transitions observed for the quasi-one-dimensional compound CsNiCl3 is established. Special attention has been devoted to the field-induced 120 degree phase transition above the multicritical point in the H-T phase diagram where the elastic constant C44 reveals a step-like variation and hysteresis effects. These results represent the first experimental evidence that the 120 degree phase transition is weakly first order and contradict the popular notion of new universality classes for chiral systems.