Half-metallicity and Slater-Pauling behavior in the ferromagnetic Heusler alloys

Half-metallic ferromagnets represent a new class of materials which attracted a lot of attention due to their possible applications in spintronics (also known as magnetoelectronics) [1]. Adding the spin degree of freedom to the conventional electronic devices has several advantages like non-volatility, increased data processing speed, decreased electric power consumption and increased integration densities [2]. The current advances in new materials and especially in the half-metals are promising for engineering new spintronic devices in the near future [2]. In these materials the two spin bands show a completely different behavior. While the majority spin band (referred also as spin-up band) shows the typical metallic behavior, the minority spin band (spin-down band) exhibits a semiconducting behavior with a gap at the Fermi level. Therefore such half-metals are ferromagnets and can be considered as hybrids between metals and semiconductors. A schematic representation of the density of states of a half-metal as compared to a normal metal and a normal semiconductor is shown in figure 1. The spinpolarization at the Fermi level is 100% and therefore these compounds should have a fully spinpolarised current and might be able to yield a 100% spininjection and thus to maximize the efficiency of magnetoelectronic devices [3].