Half-metal

Not to be confused with semi-metal.

Electronic structure of a half-metal that 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.

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.

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.

References

• Son, Y.W.; Cohen, M.L.; Louie, S.G. (2006). Half-metallic graphene nanoribbons Nature 444: 347-349. doi:10.1038/nature05180
• http://www-users.york.ac.uk/~ah566/research/half_metals.html
• http://www.tcd.ie/Physics/People/Michael.Coey/oxsen/newsletter/january98/halfmeta.htm