Fe_5-xGe₂Te₂-a New Exfoliable Itinerant Ferromagnet with High Curie Temperature and Large Perpendicular Magnetic Anisotropy

Layered van der Waals (vdW) crystals with intrinsic magnetic properties such as high Curie temperature (T-C) and large perpendicular magnetic anisotropy (PMA) are key to the development and application of spintronic devices. The ferromagnetic vdW metal Fe3-xGeTe2 (FGT) has gained prominence recently due to its high T-C (220 K) and strong PMA. Herein, a new metallic vdW ferromagnet, Fe5-xGe2Te2 or FG2T, is introduced, which is successfully synthesized and fully characterized. FG2T is a metal that orders ferromagnetically with a very sharp transition at 250 K (bulk and single-crystal thin flakes) and shows large PMA, as found by both experimental and computational studies. Novel heterostructure devices with near-room-temperature capabilities using FG2T as a spin injector are enabled by this work.