| Summary: | 碩士 === 國立雲林科技大學 === 材料科技研究所 === 101 === In this study, we used the Sub/Ta (5)/Co40Fe40B20 (X)/MgO (1)/Ta (5) (parenthetical units are in nm) as the structures to investigate the source and physical mechanism of perpendicular magnetic anisotropy (PMA) in ultrathin CoFeB films. The samples were annealed at temperature ranging from 200 °C to 350 °C after deposition, and their magnetic properties were measured by alternating gradient magnetometer (AGM). To have a deeper insight into the relationship between the film thickness and PMA, we used the x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD), which is conducted by National Synchrotron Radiation Research Center (NSRRC) in Hsinchu, to measure the magnetic as element contributions of the sample. The results from AGM show that the PMA of CoFeB films depends sensitively on film thickness and annealing temperature. The CoFeB films of thickness 1.4 nm have higher squareness and coercivity. After annealing at 350 °C, the coercivity can increases up to two times greater than the as-deposited one. Moreover, results by XAS and XMCD show that the ratios of orbital and spin moment had an pronounced effect on PMA, and the residual magnetization was the key factor of perpendicular that also had an influence on the ratio of orbital and spin moment.
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