Patterning-Induced Ferromagnetism of FeGeTe van der Waals Materials beyond Room Temperature.

Magnetic van der Waals (vdW) materials have emerged as promising candidates for spintronics applications, especially after the recent discovery of intrinsic ferromagnetism in monolayer vdW materials. There has been a critical need for tunable ferromagnetic vdW materials beyond room temperature. Here, we report a real-space imaging study of itinerant ferromagnet FeGeTe and the enhancement of its Curie temperature well above ambient temperature. We find that the magnetic long-range order in FeGeTe is characterized by an unconventional out-of-plane stripe-domain phase. In FeGeTe microstructures patterned by a focused ion beam, the out-of-plane stripe domain phase undergoes a surprising transition at 230 K to an in-plane vortex phase that persists beyond room temperature. The discovery of tunable ferromagnetism in FeGeTe materials opens up vast opportunities for utilizing vdW magnets in room-temperature spintronics devices.