PNNL

Abstract

The existence of a new class of magnetic materials displaying metallic character for one electron spin population and isulating character for the other was first populated by DeGroot et al. in 1983 based on theoretical band structure calculations of the ferromagnetic Heusler alloy NiMnSb. Since then such half metallic materials, which by definition possess 100% electron polarization at the Fermi energy, have attracted considerable theoretical, experimental, and technological interest as potential pure spin sources for use in spintronic devices. In addition to Heusler alloys (e.g. NiMnSb, PtMnSb), half metallic character has also been predicted to occur in a wide range of manganites (e.g. La1-xCaxMnO3, La1-x-SrxMnO3), metallic oxides (e.g. Fe3O4, CrO2) and CMR systems. However, such predictions have proven to be extremely difficult to confirm experimentally. Possible reasons for this include the theoretical limitations arising from the complex crystallographic structure of many such materials and limitations in applying the single electron picture to materials where strong electron correlation may be present; this is compounded by experimental difficulties posed by their structural complexity and issues such as surface contamination, segregation, and reconstruction.