Magnetic field tuning of antiferromagnetic Yb$_{3}$Pt$_{4}$

TL;DR

This study investigates how magnetic fields influence the antiferromagnetic order in Yb$_{3}$Pt$_{4}$, revealing a quantum critical endpoint where the transition becomes first order at zero temperature.

Contribution

It provides detailed experimental insights into the suppression of antiferromagnetic order and the nature of the quantum critical endpoint in Yb$_{3}$Pt$_{4}$ under magnetic fields.

Findings

Antiferromagnetic order is suppressed to zero temperature at 1.85 T.

The phase transition remains continuous for T_N > 0.

A first order transition occurs at T_N = 0, indicating a quantum critical endpoint.

Abstract

We present measurements of the specific heat, magnetization, magnetocaloric effect and magnetic neutron diffraction carried out on single crystals of antiferromagnetic Yb$_{3}$Pt$_{4}$, where highly localized Yb moments order at $T_{\rm N}=2.4$ K in zero field. The antiferromagnetic order was suppressed to $T_{\rm N}\rightarrow 0$ by applying a field of 1.85 T in the $ab$ plane. Magnetocaloric effect measurements show that the antiferromagnetic phase transition is always continuous for $T_{\rm N}>0$, although a pronounced step in the magnetization is observed at the critical field in both neutron diffraction and magnetization measurements. These steps sharpen with decreasing temperature, but the related divergences in the magnetic susceptibility are cut off at the lowest temperatures, where the phase line itself becomes vertical in the field-temperature plane. As $T_{\rm N}\rightarrow0$, the antiferromagnetic transition is increasingly influenced by a quantum critical endpoint, where $T_{\rm N}$ ultimately vanishes in a first order phase transition.