3D-Ising-type Magnetic Interactions Stabilized by the Extremely Large Uniaxial Magnetocrystalline Anisotropy in Layered Ferromagnetic Cr$_2$Te$_3$

TL;DR

This study reveals that Cr$_2$Te$_3$ exhibits 3D-Ising-type magnetic interactions with an exceptionally large uniaxial magnetocrystalline anisotropy energy, and demonstrates notable magnetocaloric effects near its Curie temperature.

Contribution

It provides the first detailed analysis linking large uniaxial anisotropy with 3D-Ising interactions in layered Cr$_2$Te$_3$, supported by experimental and theoretical insights.

Findings

Critical exponents indicate complex magnetic interactions.

Record-high uniaxial magnetocrystalline anisotropy energy.

Significant magnetocaloric effect near Curie temperature.

Abstract

We investigate the magnetocrystalline anisotropy, critical behavior, and magnetocaloric effect in ferromagnetic-layered Cr$_2$Te$_3$. We have studied the critical behavior around the Curie temperature ($T_C$) using various techniques, including the modified Arrott plot (MAP), the Kouvel-Fisher method (KF), and critical isothermal analysis (CI). The derived critical exponents $\beta$ = 0.353(4) and $\gamma$ = 1.213(5) fall in between the three-dimensional (3D) Ising and 3D Heisenberg type models, suggesting complex magnetic interactions by not falling into any single universality class. On the other hand, the renormalization group theory, employing the experimentally obtained critical exponents, suggests 3D-Ising-type magnetic interactions decaying with distance as $J(r) = r^{-4.89}$. We also observe an extremely large uniaxial magnetocrystalline anisotropy energy (MAE) of $K_u=2065$ kJ/m$^3$, the highest ever found in any Cr$_x$Te$_y$ based systems, originating from the noncollinear ferromagnetic ground state as predicted from the first-principles calculations. The self-consistent renormalization theory (SCR) suggests Cr$_2$Te$_3$ to be an out-of-plane itinerant ferromagnet. Further, a maximum entropy change of -$\Delta S_{M}^{max}\approx$ 2.08 $J/kg-K$ is estimated around $T_C$ for the fields applied parallel to the $c$-axis.