Tricritical wings and modulated magnetic phases in LaCrGe$ _{3}$ under pressure

TL;DR

This paper maps the complex pressure-temperature-magnetic field phase diagram of LaCrGe$_3$, revealing a double-wing structure and modulated magnetic phases, thus expanding understanding of quantum criticality in ferromagnets.

Contribution

It presents the first observation of a double-wing structure and modulated magnetic phases in LaCrGe$_3$, demonstrating new features in the phase diagram of metallic quantum ferromagnets.

Findings

Discovery of a double-wing structure in LaCrGe$_3$

Identification of a modulated magnetic phase under pressure

LaCrGe$_3$ exhibits both wing structure and new magnetic phases

Abstract

We determined on the temperature-pressure-magnetic field ($T$-$p$-$H$) phase diagram of the ferromagnet LaCrGe$_3$ from electrical resistivity measurements on single crystals. In ferromagnetic systems, quantum criticality is avoided either by a change of the transition order, becoming of the first order at a tricritical point, or by the appearance of modulated magnetic phases. In the first case, the application of a magnetic field reveals a wing-structure phase diagram as seen in itinerant ferromagnets such as ZrZn$_2$ and UGe$_2$. In the second case, no tricritical wings have been observed so far. Our investigation of LaCrGe$_3$ reveals a double-wing structure indicating strong similarities with ZrZn$_2$ and UGe$_2$. But, unlike these, simpler systems, LaCrGe$_3$ is thought to exhibit a modulated magnetic phase under pressure which already precludes it from a pressure-driven paramagnetic-ferromagnetic quantum phase transition in zero field. As a result, the $T$-$p$-$H$ phase diagram of LaCrGe$_3$ shows both the wing structure as well as the appearance of new magnetic phases, providing the first example of this new possibility for the phase diagram of metallic quantum ferromagnets.