Tuning the Exchange Bias Effect in 2D van der Waals Ferro‐/Antiferromagnetic Fe₃GeTe₂/CrOCl Heterostructures

Abstract

The exchange bias effect is extremely expected in 2D van der Waals (vdW) ferromagnetic (FM)/antiferromagnetic (AFM) heterostructures due to the high-quality interface. CrOCl possesses strong magnetic anisotropy at 2D limit, and is an ideal antiferromagnet for constructing FM/AFM heterostructures to explore the exchange bias effect. Here, the exchange bias effect in Fe 3 GeTe 2 (FGT)/CrOCl heterostructures through both anomalous Hall effect (AHE) and reflective magnetic circular dichroism (RMCD) measurements is studied. In the AHE measurements, the exchange bias field (H EB ) at 3 K exhibits a distinct increase from ≈150 Oe to ≈450 Oe after air exposure, and such variation is attributed to the formation of an oxidized layer in FGT by analyzing the cross-sectional microstructure. The H EB is successfully tuned by changing the FGT/CrOCl thickness and the cooling field. Furthermore, a larger H EB of ≈750 Oe at 1.7 K in FGT/CrOCl heterostructure through RMCD measurements is observed, and it is proposed that the larger H EB in RMCD measurements is related to the distribution of uncompensated spins at the interface. This work reveals several intriguing phenomena of the exchange bias effect in 2D vdW magnetic systems, which paves the way for the study of related spintronic devices.

Room-temperature spin-valve devices based on Fe3GaTe2/MoS2/Fe3GaTe2 2D van der Waals heterojunctions

“…Since the Hall device was not encapsulated, the surface layer of Fe 3 GaTe 2 maybe oxidized before testing, forming an O-Fe 3 GaTe 2 /Fe 3 GaTe 2 interface (antiferromagnet/ferromagnet) and thus causing the exchange bias. 31 The coercivities ( H C ) extracted from the AHE results (Fig. 1d) were temperature-dependent, and they declined as the temperature increased as a result of intensifying thermal fluctuations.…”

Exchange Bias State at the Crossover to 2D Ferromagnetism

“…EB in 2D materials is detected by various means such as measuring the magneto-optic Kerr effect, ,, the anomalous Hall effect, ,,,, or the reflectance magnetic circular dichroism. , The large area of the samples produced by MBE allows for direct magnetization measurements of the samples by a SQUID magnetometer. These measurements are accompanied by a study of electron transport in GdSi 2 films (see Methods for technical details).…”

“…It is not a surprise that the recent upsurge of 2D magnetism has fueled interest in the 2D limit of EB . The research is dominated by heterostructures of FGT (Fe n GeTe 2 , n = 3, 5), including FGT/CrCl 3 , FGT/CrOCl, FGT/FePS 3 , FGT/MnPS 3 , and FGT/MnPSe 3 . The number of possibilities is immense: to produce EB, FGT has been coupled with molecular layers, a non van der Waals AFM material, sandwiched between two AFM materials. , EB can also be induced by chemical modification such as surface oxidation or protonation of FGT nanoflakes; proton intercalation provides gate-tunable EB in FGT/FePS 3 .…”

2D Magnetic Semiconductor Fe3GeTe2 with Few and Single Layers with a Greatly Enhanced Intrinsic Exchange Bias by Liquid-Phase Exfoliation

“…Comparing the EB effect between liquid-phase exfoliated FGT/O-FGT nanoflakes and other vdW magnetic systems. ,,,,,,− The freshly prepared FGT/O-FGT nanoflakes possess a larger H EB value than most others, and f months later H EB is significantly enhanced to over 250% higher than the best value among the previous reports, which may be due to the more continuous O-FGT film and enough anisotropy energy to powerfully pin FGT magnetization. The related data of the references are collected at a temperature <10 K, except for the FGT/O-FGT and FGT/FePS 3 systems, which are counted at 72 and 80 K, respectively.…”