Physics:Half-metal

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The electronic structure of a half-metal. [math]\displaystyle{ E_f }[/math] is the Fermi level, [math]\displaystyle{ N(E) }[/math] 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.[1] Types of half-metallic compounds theoretically predicted so far include some Heusler alloys, such as Co
2FeSi, 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 CrO
2; some perovskites, such as LaMnO
3 and SeMnO
3; and a few more simply structured zincblende (ZB) compounds, including CrAs and superlattices. NiMnSb and CrO
2 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.[2]

Half-metals were first described in 1983, as an explanation for the electrical properties of manganese-based Heusler alloys.[3]

Some notable half-metals are chromium(IV) oxide, magnetite, and lanthanum strontium manganite (LSMO),[1] as well as chromium arsenide. Half-metals have attracted some interest for their potential use in spintronics.

References

  1. ↑ 1.0 1.1 Coey, J.M.D.; Venkatesan, M. (2002). "Half-metallic ferromagnetism: Example of CrO2". Journal of Applied Physics 91 (10): 8345–50. doi:10.1063/1.1447879. Bibcode: 2002JAP....91.8345C. 
  2. ↑ Rostami, Mohammad; Afkani, Mohammad; Torkamani, Mohammad Reza; Kanjouri, Faramarz (2020-07-01). "Bulk and surface DFT investigations of the electronic and magnetic properties of CsXNO (X = Mg, Ca and Sr) quaternary Heusler alloys". Materials Chemistry and Physics 248: 122923. doi:10.1016/j.matchemphys.2020.122923. ISSN 0254-0584. https://www.sciencedirect.com/science/article/pii/S0254058420302996. 
  3. ↑ de Groot, R. A.; Mueller, F. M.; Engen, P. G. van; Buschow, K. H. J. (20 June 1983). "New Class of Materials: Half-Metallic Ferromagnets". Physical Review Letters 50 (25): 2024–2027. doi:10.1103/PhysRevLett.50.2024. Bibcode: 1983PhRvL..50.2024D. https://pure.rug.nl/ws/files/3419075/1983PhysRevLettdeGroot.pdf. 

Further reading




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