| Summary: | 碩士 === 國立交通大學 === 物理研究所 === 101 === The magnetoresistance change of nonlocal spin valve is currently a hot research topic that has been widely used in the computer’s hard disk read heads.
The geometry of our sample is that a non-magnetic Au film is connected by two ferromagnetic NiFe contacts. One NiFe electrode is spin-injector F1 and another is spin-detector F2. When spin polarization electrons inject from F1 into Au, and a non-equilibrium spin accumulation is induced in Au. The spin accumulation is manifested in the Au band structure as a splitting of the Fermi levels between spin-up and spin-down electrons. The detector is utilized to measure the spin accumulation. Depending on the relative orientations of the detector spin and the spin accumulation, a voltage contrast can be measured between F2 and Au. When F2 is aligned parallel to the spin accumulation, its Fermi level is aligned with the upper Fermi level in Au, and thus exhibits a high resistance. Otherwise a low resistance is measured. The resistance difference (∆R) is our goal to be measured. We can calculate the spin diffusion length when we know the ∆R. In my system, the max ∆R is 30mΩ and the max spin diffusion length is 2.8 micrometer.
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