• There is (collinear) magnetic order.
  • Conduction is metallic, like a common metal.
  • The spin susceptibility vanishes, like an insulator. Other contributions to the susceptibility remain.
  • The total (spin) magnetic moment in the primitive cell is an integer.
  • NMR relaxation rate 1/T1 is non-Korringa, because low energy spin flips are disallowed.
  • Spin-polarized spectroscopy at the Fermi level. In practice, there are many complications.
  • Spin-polarized positron annihilation. Also difficult, must identify Fermi surface of one spin and establish that there is no Fermi surface for the other spin.
  • Tunneling: on-off characteristics, ideally. Interfaces can introduce magnetic centers that flip spins, and other non-idealities can occur at the interfaces.
  • Thermodynamic and transport properties(?). This is still an open question, because understanding of the half-metallic state is incomplete.

Physical Properties of Half-Metallic Ferromagnets

See R. E. Rudd and W. E. Pickett, Phys. Rev. B 57, 557 (1998)
The ordered double perovskite crystal structure, also called the elpasolite or cryolite structure. Often the MO6 octrahedra are rotated around a <100>, <110> or <111> axis.