Magnetic moment compensated Half-Heusler alloys
ABSTRACT :
Spintronics has attracted great interest among researchers because of the potential to simultaneously tune both charge and spin in solids state materials that may lead to the development of novel multifunctional devices. The operation of a spintronic device in general involves the injection of spin polarized electrons from a magnetic material in to a non-magnetic medium which is then controlled or manipulated and finally detected by another magnetic material. To achieve high spin injection efficiency in these devises, spin injection electrode with high spin polarization is required. Half metallic ferromagnets which have 100% spin polarized charge carriers are ideally suited for such applications. However, half-metallic ferromagnets produce high stray fields and energy losses, which hinder device performance. Hence there is a search for half metal with zero magnetic moment. In 1995, van Leuken and de Groot proposed a new class of materials called half metallic antiferromagnets but symmetry does not allow half-metallic antiferromagnets. However, in the case of crystallograficallly in-equivalent magnetic sub lattices with antiparallel alignment of their spins, half-metallicity combined with a zero net magnetic moment can be achieved giving rise to half-metallic compensated ferrimagnets. Even though there are different materials exhibiting half metallicity, Heusler alloys are interesting because of the high tunability of their magnetic structure due to the existence of one or more magnetic sub lattices. The results on the structural and magnetic properties of two Half Heusler systems with full magnetic moment compensation will be presented.