Studies of spin-valve IrMn/CoFeB/Ta/CoFeB structure by Transmission electron microscopy

• Main Author: 蔡慧敏
• Other Authors: 洪連輝
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/64715691033457071444

碩士 === 國立彰化師範大學 === 物理學系 === 99 === We have investigated the interlayer coupling in IrMn/CoFeB/Ta /CoFeB spin valve structure by using the tunnelling electron microscopy (TEM). In this study, we observe antifrerromagnetic coupling properties when Ta spacers are 0.92 nm and 1.30 nm. Then we fixed Ta thickness of 1 nm, and changed IrMn thickness to observe the exchange coupling between IrMn and bottom CoFeB. We find it still has pining effect until IrMn thickness greater than 14 nm. Thermal annealing process also has an influence on IrMn pinning effect. We investigate the exchange coupling in bottom pinned structure IrMn/CoFeB/Ta/CoFeB with different annealing temperatures. The results show that thermal annealing enhances IrMn pining effect, and the exchange bias exists after higher thermal annealing with IrMn thickness greater than 20 nm. Besides, the exchange bias exists at 300 oC thermal annealing with IrMn thickness 20 nm, but in IrMn 25 nm structure, exchange bias exist at 350 oC. IrMn(111) structure can enhance exchange bias, and by TEM analysis, we can find IrMn have a good (111) twxture after higher thermal annealing.