Evolution of ground state in Cr2Te3 single crystal under applied magnetic field

Abstract

Two-dimensional magnetic materials hold great promise for applications toward efficient data storage and transfer. It would be a huge advantage if their ground-state properties had strong responses against external stimulations, such as magnetic and electric fields. Here, we report several intriguing discoveries in single-crystal ${\mathrm{Cr}}_{2}{\mathrm{Te}}_{3}$. Based on comprehensive specific heat, differential scanning calorimetry, variable-temperature x-ray diffraction, and linear-thermal-expansion measurements, we find that ${\mathrm{Cr}}_{2}{\mathrm{Te}}_{3}$ has a low-temperature ferromagnetic (FM) ground-state phase, which changes to an antiferromagnetic (AFM) phase when temperature is increased to ${T}_{\mathrm{C}}$ = 160 K. This FM-AFM transition is a first-order phase transition, and the transition temperature can be further enhanced to 178 K by a moderate magnetic field. At the same time, the first-order phase transition will transform into a second-order phase transition, indicating strong spin-lattice coupling (SLC). A second-order AFM-paramagnetic phase transition emerges at ${T}_{\mathrm{N}}=181$ K. This AFM phase is gradually suppressed by the magnetic field and eventually disappears at a critical field of 0.48 T. The SLC results in a notable negative-thermal-expansion coefficient of $\ensuremath{-}17.2$ ppm/K and a remarkable magnetostriction coefficient of 44.7 ppm/T at 200 K. With the assistance of first-principles density functional theory calculations and Monte Carlo simulations, we conclude that the collinear FM, canted FM, and AFM configurations in ${\mathrm{Cr}}_{2}{\mathrm{Te}}_{3}$ depend on the temperature and applied magnetic field. Our work reveals the highly tunable magnetic phases and SLC in ${\mathrm{Cr}}_{2}{\mathrm{Te}}_{3}$, which will be helpful for developing the potential functionalities of this material.