Spin glass behavior in amorphous Cr2Ge2Te6 phase-change alloy

TL;DR

This study shows that amorphous Cr2Ge2Te6 retains spin polarization but transitions to a spin glass state below 20 K, with potential applications in magnetic phase-change devices.

Contribution

It reveals the magnetic behavior of amorphous Cr2Ge2Te6, including the spin glass transition and its microscopic origin, expanding understanding of phase-change magnetic materials.

Findings

Amorphous Cr2Ge2Te6 preserves spin polarization.

A spin glass transition occurs below 20 K.

Bond distortions cause the magnetic transition.

Abstract

The layered crystal structure of Cr2Ge2Te6 shows ferromagnetic ordering at the two-dimensional limit, which holds promise for spintronic applications. However, external voltage pulses can trigger amorphization of the material in nanoscale electronic devices, and it is unclear whether the loss of structural ordering leads to a change in magnetic properties. Here, we demonstrate that Cr2Ge2Te6 preserves the spin-polarized nature in the amorphous phase, but undergoes a magnetic transition to a spin glass state below 20 K. Quantum-mechanical computations reveal the microscopic origin of this transition in spin configuration: it is due to strong distortions of the Cr-Te-Cr bonds, connecting chromium-centered octahedra, and to the overall increase in disorder upon amorphization. The tunable magnetic properties of Cr2Ge2Te6 could be exploited for multifunctional, magnetic phase-change devices that switch between crystalline and amorphous states.