Preparation And Study On The Spin Transport Properties Of Magnetic Half-metals And Diluted Magnetic Semiconductors

Spin electrons were introduced by spintronics, which extend research domain of traditional electronics. It is a promising candidate for the application of magnetic sensors, high density magnetic recording materials, read-out magnetic heads and magnetic random access memories. Researching the electronic transportation properties of half-matal material, fabrication of films with high MR at room temperature and exploring the origin of ferromagnetic in deluited magnetic semiconductors has becomes one focus in the field of condensed matter physics. This is also the aim and major work in this thesis.Polycrystalline Fe₃O₄ films and Cr-doped TiO₂ films were deposited by using reactive magnetron sputtering apparatus. We investigate theirs microcosmic structure, ingredient, resistivity, magnetoresistance, hysteresis loop and Hall effects.Polycrystalline Fe₃O₄ grain films deposited at room temperature and acquire a biggish MR value about -9% in 80K in it. The measurements of hysteresis loop, resistivity, magnetoresistance and Hall effects suggest a spin polarized tunnelling mechanism is the main mechanism in polycrystalline Fe₃O₄ films.Electronic transportation properties variety with the oxygen contents of films compared with nonstoichiometric structure Fe₃O₄ films. This illuminate magnetism between adjacent grains strongly influenced the electronic transportation properties of the films. Diluted magnetic semiconductors Cr-doped TiO₂ films were deposited by usingmagnetron sputtering apparatus in room temperature. Effect of sputtering power of the Cr and annealing temperature on structure and transport properties of films was also studied. We proved that Cr is dopant atoms in amorphous CrxTi1?xO2. Magnetic moments of Cr atoms decreasing with Cr content increasing. After annealing, the structure of the films change to anatase and the magnetism disappeared. These phenomenons show that ferromagnetism of diluted magnetic semiconductor Cr-doped TiO₂ films belong to itselfs. The structure defects of the material strongly influence the magnetism of the films.