Imaging current control of magnetization in Fe₃GeTe₂ with a widefield nitrogen-vacancy microscope

Abstract

Van der Waals (vdW) magnets are appealing candidates for realising spintronic devices that exploit current control of magnetization (e.g. switching or domain wall motion), but so far experimental demonstrations have been sparse, in part because of challenges associated with imaging the magnetization in these systems. Widefield nitrogen-vacancy (NV) microscopy allows rapid, quantitative magnetic imaging across entire vdW flakes, ideal for capturing changes in the micromagnetic structure due to an electric current. Here we use a widefield NV microscope to study the effect of current injection in thin flakes (∽10 nm) of the vdW ferromagnet Fe3GeTe2 (FGT). We first observe current-reduced coercivity on an individual domain level, where current injection in FGT causes substantial reduction in the magnetic field required to locally reverse the magnetisation. We then explore the possibility of current-induced domain-wall motion, and provide preliminary evidence for such a motion under relatively low current densities, suggesting the existence of strong current-induced torques in our devices. Our results illustrate the applicability of widefield NV microscopy to imaging spintronic phenomena in vdW magnets, highlight the possibility of efficient magnetization control by direct current injection without assistance from an adjacent conductor, and motivate further investigations of the effect of currents in FGT and other vdW magnets.

Broken Inversion Symmetry in Van Der Waals Topological Ferromagnetic Metal Iron Germanium Telluride

“…Recent investigations [29,34] discover the gigantic intrinsic spinorbit torque by current in a single FGT without any heavy-metal layer, which has also been confirmed by sequential works [35][36][37][38][39] from different research groups. But in principle, spin-orbit torque cannot be generated by current in a centrosymmetric system like FGT since inversion symmetry breaking is required for producing the current-driven spin polarization.…”

Quantum sensing of radio-frequency signal with NV centers in SiC

“…Among them, negatively charged nitrogen-vacancy (NV) centers in diamond have shown prominent spin properties and attracted extensive studies (6)(7)(8). NV in diamond has been used to detect individual proteins and image magnetic domains in van der Waals materials (9,10). Furthermore, it has demonstrated high-resolution nuclear magnetic resonance spectroscopy of biological structures at both nano-and micrometer spatial domains using a synchronized readout technique (11)(12)(13).…”

Imaging the Magnetic Anisotropy in Ultrathin Fe4GeTe2 with a Nitrogen-Vacancy Magnetometer

“…The discovery of two-dimensional (2D) van der Waals (vdW) magnets has opened up new possibilities for studying low-dimensional magnetic phase transitions and designing 2D spintronic devices. − However, the applications of most vdW magnets are limited by the relatively low critical temperatures ( T c ). In recent years, 2D Fe n GeTe 2 ( n = 3, 4, 5) has attracted significant attention. ,− With increasing n , the spin-exchange interaction and anisotropy increase. Accordingly, the fluctuation effect is suppressed, leading to enhanced T c , with T c values of ∼220, 270, and 300 K for bulk materials with n = 3, 4, and 5, respectively.…”