Spin Glass Behavior in Amorphous Cr₂Ge₂Te₆ Phase-Change Alloy

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, it is demonstrated 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 CrTeCr bonds, connecting chromium-centered octahedra, and to the overall increase in disorder upon amorphization. The tunable magnetic properties of Cr₂Ge₂Te₆ can be exploited for multifunctional, magnetic phase-change devices that switch between crystalline and amorphous states.