page_title: Iron germanide
section_title: Magnetism
hierarchical_section_title: Iron germanide / Magnetism
caption_attribution_description: Spin textures and magnetic phase diagrams of an FeGe lamella: a, b Phase diagrams of the ~120 nm FeGe lamella for out-of-plane and in-plane applied magnetic field, respectively, as determined magnetic x-ray diffraction. Schematics of each field configuration are shown as insets. In a, boundaries between the helical (H) and skyrmion lattice (SkL) states are displayed by yellow and magenta dots. The expected boundary between the indistinguishable conical (C) and field polarised (FP) states is estimated by the purple dashed line. The zero-field cooling (ZFC) and field cooling (FC) procedures are indicated. In b, yellow, magenta and purple dots boundaries indicate the boundaries between the helical (H), helical rotation transition (T), conical (C) and field polarised (FP) states. c–e Schematic illustrations of the spin textures as they are expected to appear in a thin lamella.
context_page_description: Iron germanide is an intermetallic compound, a germanide of iron. At ambient conditions it crystallizes in three polymorphs with monoclinic, hexagonal and cubic structures. The cubic polymorph has no inversion center, it is therefore helical, with right-hand and left-handed chiralities.
context_section_description: FeGe is extensively studied for its unusual magnetic properties. Electron spins in this material show dissimilar, yet regular spatial arrangements at different values of applied magnetic field. Those arrangements are named helical, skyrmion lattice, and conical. 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. As a result, skyrmions have potential application in ultrahigh-density magnetic storage devices. 
  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. The disadvantage of FeGe over MnSi is its polymorphism, which hinders the growth of large homogeneous crystals.
caption: 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).
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