Probing Magnetism in Insulating Cr₂Ge₂Te₆ by Induced Anomalous Hall Effect in Pt

Abstract

Two-dimensional ferromagnet Cr 2 Ge 2 Te 6 (CGT) is so resistive below its Curie temperature that probing its magnetism by electrical transport becomes extremely difficult. By forming heterostructures with Pt, however, we observe clear anomalous Hall effect (AHE) in 5 nm thick Pt deposited on thin (< 50 nm) exfoliated flakes of CGT. The AHE hysteresis loops persist to ~ 60 K, which matches well to the Curie temperature of CGT obtained from the bulk magnetization measurements. The slanted AHE loops with a narrow opening indicate magnetic domain formation, which is confirmed by low-temperature magnetic force microscopy (MFM) imaging. These results clearly demonstrate that CGT imprints its magnetization in the AHE signal of the Pt layer. Density functional theory calculations of CGT/Pt heterostructures suggest that the induced ferromagnetism in Pt may be primarily responsible for the observed AHE. Our results establish a powerful way of investigating magnetism in 2D insulating ferromagnets which can potentially work for monolayer devices.

Efficient Spin‐Orbit Torque Switching of the Semiconducting Van Der Waals Ferromagnet Cr2Ge2Te6

“…A stack consisting of HMs such as Pt or W deposited on an insulating FM such as Tm 3 Fe 5 O 12 (TMIG) has shown to result in an induced anomalous Hall effect in the metal, thus providing an electrical path toward reading the magnetization of insulating FMs . In fact, a recent study has used a similar approach to characterize a CGT/Pt heterostructure . In this article, we utilize the induced AHE in Ta to study the magnetization properties of CGT for various thicknesses.…”

Van der Waals magnets: Wonder building blocks for two‐dimensional spintronics?

“…D, Kerr angle measured at 40 K at negative (upper panel) and positive gate (lower panel) voltages, respectively . E, Optical micrograph of CGT/Pt heterostructure . F, Anomalous Hall hysteresis loop at 4 K for the CGT/Pt device…”

“…E, Optical micrograph of CGT/Pt heterostructure . F, Anomalous Hall hysteresis loop at 4 K for the CGT/Pt device…”

“…The magnetism of CGT has also been studied electrically by anomalous Hall effect . It has been shown that CGT devices gated near the ferromagnetic, metallic region showed marked resistance changes at ~±0.2 T .…”

“…For its bilayer, the characteristic Raman peaks are observed to shift from its original positions after 90 minutes of air exposure. The group of Shi et al has further studied the thermal effects on the oxidation of CGT flakes . No obvious sign of oxidation‐related degradation can be observed until the flakes are heated beyond 120 K.…”