Complex magnetic phase diagram with a small phase pocket in a three-dimensional frustrated magnet CuInCr$_{4}$S$_{8}$

TL;DR

This study reveals a complex magnetic phase diagram in the frustrated magnet CuInCr$_{4}$S$_{8}$, including a small helimagnetic phase pocket, driven by magnetic frustration and thermal fluctuations, with distinct magnetostrictive and magnetocapacitive responses.

Contribution

It experimentally uncovers a previously unobserved small helimagnetic phase pocket in CuInCr$_{4}$S$_{8}$, supporting the existence of a fluctuation-driven multiple-q state in a frustrated magnet.

Findings

Discovery of a small helimagnetic phase in CuInCr$_{4}$S$_{8}$

Anomalous magnetostrictive and magnetocapacitive responses associated with the phase

High-entropy behavior observed near the phase pocket

Abstract

Frustrated magnets with a strong spin-lattice coupling can show rich magnetic phases and the associated fascinating phenomena. A promising platform is the breathing pyrochlore magnet CuInCr$_{4}$S$_{8}$ with localized $S=3/2$ Cr$^{3+}$ ions, which is proposed to be effectively viewed as an $S=6$ Heisenberg antiferromagnet on the face-centered-cubic lattice. Here, we unveil that CuInCr$_{4}$S$_{8}$ exhibits a complex magnetic phase diagram with a small phase pocket ($A$ phase) by means of magnetization, magnetostriction, magnetocapacitance, and magnetocaloric-effect measurements in pulsed high magnetic fields of up to 60 T. Remarkably, the appearance of $A$ phase is accompanied by anomalous magnetostrictive and magnetocapacitive responses, suggesting the emergence of helimagnetism in contrast to the neighboring commensurate magnetic phases. Besides, the high-entropy nature is confirmed in the high-temperature side of $A$ phase. These features are potentially related to a thermal fluctuation-driven multiple-$q$ state caused by the magnetic frustration, which has been theoretically predicted but yet experimentally undiscovered.