Magnetic Surface States in High Polarization Materials

Surfaces are often different materials, and typically have a different electronic structure from the bulk and since the dawn of surface science, surface-localized electronic states, surface states, have been extensively studied and investigated with growing accuracy. Of particular importance to spintronics are magnetic surface states. Interfaces will play a very important role in many spintronics devices, yet the interface properties are often ignored, poorly understood or badly characterized. For many nominally half metal materials, materials that in some ground state calculations exhibit 100% spin polarization, the magnetic surface states may significantly reduce the effective spin polarization. We review the magnetic surface states of several well known and often highly touted high spin polarized materials such as NiMnSb, Fe3O4, CoS2 and CrO2. Finally, we summarize surface state measurements of magnetoelectric antiferromagnets Cr2O3, which has electrically controllable net surface spins, a major complication to the study of CrO2 by photoemission.