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Field of spintronics is concerned with search for highly spin-polarized materials with the aim of enhancing tunnelling magnetoresistance of magnetic tunnel junctions, which are active members of magnetic random access memory elements. The second application of spintronics is spin transistors and the underlying basic concept of spin injection. Injection of a spin polarized current from a ferromagnet into a semiconductor is also necessary in order to carry out qubit (quantum bit) operations required for quantum computing. The first theoretical demonstration of a spin Field Effect Transistor was done in 1990. It has not yet been realized in experiments, mainly because it requires spin injection from a ferromagnetic metal (for example Fe) into a semiconductor. This has been shown to be practically impossible due to the large conductivity mismatch between a metal and a semiconductor. The use of ferromagnetic materials with a spin polarization as large as possible can help to efficient injection of spin into semiconductor. So called half-metallic ferromagnets are the ultimate materials in this respect since 100% spin polarization is expected from these materials.
Here we present a theoretical and experimental electronic structure study of the recently reinvestigated shandite Co3Sn2S2. Previous experimental results from magnetic susceptibility, specific heat, and resistivity measurements on powder samples showed a phase transition to a ferromagnetic metallic state at 177 K with a saturation moment of 0.87μB/f.u. Full potential electronic structure calculations within LSDA result in a half-metallic ferromagnetic ground state with a moment of 1μB/f.u. and a tiny gap in the minority spin channel. Presented experimental results obtained on polycrystalline Co3Sn2S2 samples by means of ultraviolet as well as x-ray photoelectron spectroscopies were compared with LSDA band structure calculations. Extracted from the experimental spectra, partial and total density of states, are in good agreement with presented theoretical results and give an evidence that this compound can be related to the class of half-metallic ferromagnets. |