| Summary: | 碩士 === 國立雲林科技大學 === 材料科技研究所 === 102 === In this thesis, we focused on switching pMTJ’s magnetic moments by the spin Hall effect (SHE). The spin current can be generated in nonmagnetic materials by theSHE, which spin up and spin down currents accumulate on the surface by charge current. We incooperated the perpendicular magnetic tunnel junctions (pMTJ) with SHE of structure CoFeB / MgO / CoFeB, which have the advantages of high magnetoresistance, small writing current and good thermal stability. To increase the spin current amplitude, Ta served as the bottom electrode.
The pMTJ structure is SiOx / Ta (X nm) / Co40Fe40B20 (1.2 nm) / MgO (2nm) / Co20Fe60B20 (2.3 nm) / Ta (5 nm) / Ru (5 nm), where Co40Fe40B20 served as free layer while Co20Fe60B20 served as fixed layer. Both the thickness of Ta and annealing procedure were varied to improve the magnetic properties. The samples were then patterned into 6x8 m2 devices to make resistance measurements.
The magnetoresistance (MR) measurements show that the samples of different Ta thicknesses, 25 and 15 nm, result in different MR ratio 33% and 27%, respectively. The resistance and current measurement of three-terminal SHE device. We prepare the electrical components with bottom electrode Ta 25 nm, the result shows that the ratio between high and low resistance is about 31% when pass into a maximum current in 8 mA. In this experiment, we transferred the spin torque successfully by spin Hall effect, and it shows that the resistance changed significantly with increasing currents.
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