Fe_5−<i>x</i>Ge₂Te₂—a New Exfoliable Itinerant Ferromagnet with High Curie Temperature and Large Perpendicular Magnetic Anisotropy

Abstract

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 Fe 3− x GeTe 2 (FGT) has gained prominence recently due to its high T C (220 K) and strong PMA. Herein, a new metallic vdW ferromagnet, Fe 5− x Ge 2 Te 2 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.