# Magnetic Anisotropy and Low Field Magnetic Phase Diagram of Quasi Two-Dimensional Ferromagnet Cr$_2$Ge$_2$Te$_6$

## TL;DR

This study explores the magnetic anisotropy and phase diagram of Cr$_2$Ge$_2$Te$_6$, revealing a complex interplay of magnetic field, temperature, and anisotropy in a quasi-two-dimensional ferromagnetic system.

## Contribution

It provides the first detailed magnetic phase diagram of Cr$_2$Ge$_2$Te$_6$ under different field orientations, highlighting universal behaviors in similar 2D honeycomb ferromagnets.

## Key findings

- Cr$_2$Ge$_2$Te$_6$ has a Curie temperature of 65 K.
- Anisotropic magnetic behavior with an easy axis perpendicular to layers.
- Identification of a downturn in magnetization under fields in the hard plane.

## Abstract

In this work we present a comprehensive investigation on magnetic and thermodynamic properties of the two-dimensional layered honeycomb system Cr$_2$Ge$_2$Te$_6$. Using magnetization and specific heat measurements under magnetic field applied along two crystallographic directions we obtain the magnetic phase diagram for both directions. Cr$_2$Ge$_2$Te$_6$ is a ferromagnet with a Curie temperature $T_C=65$ K and exhibits an easy magnetization axis perpendicular to the structural layers in the $ab$-plane. Under magnetic fields applied parallel to the hard plane $ab$ below the magnetic saturation, a downturn with an onset temperature $T\textrm{*}$ is observed in the temperature dependent magnetization curve. $T\textrm{*}$ shows a monotonous shift towards lower temperatures with increasing field. The nature of this anisotropic and specific behavior for fields in the hard plane is discussed as an interplay among field, temperature and effective magnetic anisotropy. Similarities to structurally related compounds such as CrX$_3$ (X = Br, I) hint towards a universality of this behavior in ferromagnetic quasi two-dimensional honeycomb materials.