Giant coercivity enhancement in a room-temperature van der Waals magnet through substitutional metal-doping.

Fe x GeTe 2 ( x = 3, 4, and 5) systems, two-dimensional (2D) van der Waals (vdW) ferromagnetic (FM) metals with high Curie temperatures ( T C ), have been intensively studied to realize all-2D spintronic devices. Recently, an intrinsic FM material Fe 3 GaTe 2 with high T C (350-380 K) has been reported. As substitutional doping changes the magnetic properties of vdW magnets, it can be a powerful means for engineering the properties of magnetic materials. Here, the coercive field ( H c ) is substantially enhanced by substituting Ni for Fe in (Fe 1- x Ni x ) 3 GaTe 2 crystals. The introduction of a Ni dopant with x = 0.03 can enhance the value of H c up to ∼200% while maintaining the FM state at room temperature. As the doping level increases, T C decreases, whereas H c increases up to 7 kOe at x = 0.12, which is the highest H c reported so far. The FM characteristic is almost suppressed at x = 0.68 and a spin glass state appears. The enhancement of H c resulting from Ni doping can be attributed to domain pinning induced by substitutional Ni atoms, as evidenced by the decrease in magnetic anisotropy energy in the crystals upon Ni doping. Our findings provide a highly effective way to control the H c of the 2D vdW FM metal Fe 3 GaTe 2 for the realization of Fe 3 GaTe 2 based room-temperature operating spintronic devices.