Spin-glass states generated in a van der Waals magnet by alkali-ion intercalation

TL;DR

This study demonstrates that alkali-ion intercalation in a van der Waals magnet induces magnetic frustration, leading to spin-glass states, increased Curie temperature, and altered magnetic anisotropy, revealing a new method to control magnetic ground states.

Contribution

It introduces intercalation as a novel approach to generate frustrated spin states and manipulate magnetic properties in layered van der Waals materials.

Findings

Intercalation of Na atoms induces spin-glass states in Cr2Ge2Te6.

Curie temperature increases from 66 K to 240 K due to intercalation.

Magnetic easy-hard axis switching occurs after intercalation.

Abstract

Tuning magnetic properties in layered van der Waals (vdW) materials has captured a significant attention due to the efficient control of ground-states by heterostructuring and external stimuli. Electron doping by electrostatic gating, interfacial charge transfer and intercalation is particularly effective in manipulating the exchange and spin-orbit properties, resulting in a control of Curie temperature ($T_{\text{C}}$) and magnetic anisotropy. Here, we discover an uncharted role of intercalation to generate magnetic frustration. As a model study, we intercalate Na atoms into the vdW gaps of pristine Cr$_2$Ge$_2$Te$_6$ (CGT) where generated magnetic frustration leads to emerging spin-glass states coexisting with a ferromagnetic order. A series of dynamic magnetic susceptibility measurements/analysis confirms the formation of magnetic clusters representing slow dynamics with a distribution of relaxation times. The intercalation also modifies other macroscopic physical parameters including the significant enhancement of $T_{\text{C}}$ from 66\,K to 240\,K and the switching of magnetic easy-hard axis direction. Our study identifies intercalation as a unique route to generate emerging frustrated spin states in simple vdW crystals.