The electronic structure of a half-metal. E f {\displaystyle E_{f}} is the Fermi level, N ( E ) {\displaystyle N(E)} is the density of states for spin down (on the left) and spin up (on the right). In this case, the half-metal is conducting in the minority spin channel.

A half-metal is any substance that acts as a conductor to electrons of one spin orientation, but as an insulator or semiconductor to those of the opposite orientation. Although all half-metals are ferromagnetic (or ferrimagnetic), most ferromagnets are not half-metals. Many of the known examples of half-metals are oxides, sulfides, or Heusler alloys. Types of half-metallic compounds theoretically predicted so far include some Heusler alloys, such as Co2FeSi, NiMnSb, and PtMnSb; some Si-containing half–Heusler alloys with Curie temperatures over 600 K, such as NiCrSi and PdCrSi; some transition-metal oxides, including rutile structured CrO2; some perovskites, such as LaMnO3 and SeMnO3; and a few more simply structured zincblende (ZB) compounds, including CrAs and superlattices. NiMnSb and CrO2 have been experimentally determined to be half-metals at very low temperatures.

In half-metals, the valence band for one spin orientation is partially filled while there is a gap in the density of states for the other spin orientation. This results in conducting behavior for only electrons in the first spin orientation. In some half-metals, the majority spin channel is the conducting one while in others the minority channel is.

Half-metals were first described in 1983, as an explanation for the electrical properties of manganese-based Heusler alloys.

Some notable half-metals are chromium(IV) oxide, magnetite, and lanthanum strontium manganite (LSMO), as well as chromium arsenide. Half-metals have attracted some interest for their potential use in spintronics.

In July 2025, researchers reported the first experimental realization of a two-dimensional (2D) half-metal: a bilayer FePd alloy grown on a Pd(001) substrate. This system, composed of only two atomic layers, exhibits complete spin polarization at the Fermi level, as demonstrated by momentum and spin-resolved photoelectron spectroscopy. The half-metallicity is confined to the two-atomic-layer limit and modulated by the Fe-Pd content within the bilayer. The FePd bilayer remains half-metallic at room temperature, is structurally robust, and exhibits tunable electronic properties through variation in Fe content. These features make it a promising platform for nanoscale spintronic applications such as spin filters and spin–orbit torque devices.

Further reading

  • Guezlane, M; Baaziz, H; El Haj Hassan, F; Charifi, Z; Djaballah, Y (2016). "Electronic, magnetic and thermal properties of Co2CrxFe1−xX (X=Al, Si) Heusler alloys: First-principles calculations". Journal of Magnetism and Magnetic Materials. 414: 219–26. Bibcode:. doi:.
  • Son, Young-Woo; Cohen, Marvin L; Louie, Steven G (2006). "Half-metallic graphene nanoribbons". Nature. 444 (7117): 347–9. arXiv:. Bibcode:. doi:. PMID . S2CID .
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