[Prof. Jun Sung Kim]Tunable high-temperature itinerant antiferromagne…

Caption (Center) Crystal structure of a newly-synthesized van der Waals magnet (Fe,Co)₄GeTe₂ and the optical image of the single crystal. (Left and Right) Four different magnetic states with the ferromagnetic/antiferromagnetic spin configurations and the out-of-plane/in-plane spin orientations.

[Prof. Jun Sung Kim]Tunable high-temperature itinerant antiferromagnetism in a van der Waals magnet 

Discovery of two dimensional (2D) magnets, showing intrinsic ferromagnetic (FM) or antiferromagnetic (AFM) orders, has accelerated development of novel 2D spintronics, in which all the key components are made of van der Waals (vdW) materials and their heterostructures. High-performing and energy-efficient spin functionalities have been proposed, often relying on current-driven manipulation and detection of the spin states. In this regard, metallic vdW magnets are expected to have several advantages over the widely-studied insulating counterparts, but have not been much explored due to the lack of suitable materials. Here, we report tunable itinerant ferro- and antiferromagnetism in Co-doped Fe4GeTe2 utilizing the vdW interlayer coupling, extremely sensitive to the material composition. This leads to high TN antiferromagnetism of TN ~ 226 K in a bulk and ~210 K in 8 nm-thick nanoflakes, together with tunable magnetic anisotropy. The resulting spin configurations and orientations are sensitively controlled by doping, magnetic field, and thickness, which are effectively read out by electrical conduction. These findings manifest strong merits of metallic vdW magnets as an active component of vdW spintronic applications.