Ferromagnetic Quantum Critical Point Avoided by the Appearance of Another Magnetic Phase in LaCrGe$_3$ under Pressure

TL;DR

This study maps the pressure-temperature phase diagram of LaCrGe$_3$, revealing that a new magnetic phase emerges to avoid ferromagnetic quantum criticality, supported by experimental and theoretical evidence.

Contribution

First comprehensive phase diagram of LaCrGe$_3$ showing avoided quantum criticality through a new magnetic phase, combining experimental measurements and density functional theory calculations.

Findings

Ferromagnetic phase suppressed near 2.1 GPa

Appearance of a likely modulated antiferromagnetic phase

Density functional theory suggests near degeneracy of AFM states with small wave vectors

Abstract

The temperature-pressure phase diagram of the ferromagnet LaCrGe$_3$ is determined for the first time from a combination of magnetization, muon-spin-rotation and electrical resistivity measurements. The ferromagnetic phase is suppressed near $2.1$~GPa, but quantum criticality is avoided by the appearance of a magnetic phase, likely modulated, AFM$_Q$. Our density functional theory total energy calculations suggest a near degeneracy of antiferromagnetic states with small magnetic wave vectors $Q$ allowing for the potential of an ordering wave vector evolving from $Q=0$ to finite $Q$, as expected from the most recent theories on ferromagnetic quantum criticality. Our findings show that LaCrGe$_3$ is a very simple example to study this scenario of avoided ferromagnetic quantum criticality and will inspire further study on this material and other itinerant ferromagnets.