Iron germanide

Electron spins in this material show dissimilar, yet regular spatial arrangements at different values of applied magnetic field.

They can be controlled not only by temperature and magnetic field, but also by electric current, and the current density required for manipulating skyrmions (~106 A/m2) is approximately one million times smaller than that needed for moving magnetic domains in traditional ferromagnets.

[2] The helical, conical and skyrmion structures are not unique to FeGe; they are also found in MnSi, MnGe and similar compounds, but contrary to those materials, the observation of magnetic ordering patterns in FeGe does not require cryogenic cooling.

[2] The disadvantage of FeGe over MnSi is its polymorphism, which hinders the growth of large homogeneous crystals.

[1] Polycrystalline FeGe is produced by vacuum arc remelting, spark plasma sintering, or high-pressure high-temperature treatment of a mixture of elemental iron and germanium.

Experimental phase diagrams when the applied magnetic field H is directed perpendicular or parallel to a FeGe thin film. With increasing magnetic field, the magnetic ordering of FeGe spins changes from helical (H) to skyrmion (SkL), conical (C) and field polarized (FP, i.e. regular ferromagnetic).
Simulated and measured (by STXM ) images of helical, skyrmion and conical phases. Scale bar: 200 nm