Half-metal

A half-metal is any substance that acts as a conductor to electrons of one spin orientation, but as an insulator to those of the opposite orientation.

Conduction in magnetic materials is due to two types of electron, i.e., electrons with spin up and electrons with spin down.

In half-metals, the valence band related to one type of these electrons is fully filled and the other is partially filled. So only one type of electrons (the spin type with the partially filled band) can pass through it, because full bands have a net conductance of zero.

A schematic diagram of the band structure of a half-metal is shown below.

Some notable half-metals are chromium(IV) oxide and Perovskite lanthanum strontium manganite (LSMO); as well as chromium arsenide.

References

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