Boron diffusion induced symmetry reduction and scattering in CoFeB/MgO/CoFeB magnetic tunnel junctions

被引：30
|
作者：
Bai, Zhaoqiang [1 ,2 ]
Shen, Lei [1 ]
Wu, Qingyun [1 ]
Zeng, Minggang [1 ]
Wang, Jian-Sheng [1 ]
Han, Guchang [2 ]
Feng, Yuan Ping [1 ]
机构：
[1] Natl Univ Singapore, Dept Phys, Singapore 117542, Singapore
[2] Agcy Sci Technol & Res, Data Storage Inst, Singapore 117608, Singapore
来源：
PHYSICAL REVIEW B | 2013年 / 87卷 / 01期
关键词：
ROOM-TEMPERATURE; MAGNETORESISTANCE;
D O I：
10.1103/PhysRevB.87.014114
中图分类号：
T [工业技术];
学科分类号：
08 ;
摘要：
By first-principles analysis, we investigate the effect of thermal annealing on structural stability of CoFeB/MgO(thin)/CoFeB magnetic tunnel junctions. The calculated phonon dispersion indicates that Mg3B2O6 (kotoite) is a stable spacer after annealing due to B diffusion into MgO. The calculated tunneling magnetoresistance (TMR) of CoFe/kotoite/CoFe is 210%, which is in good agreement with the available experimental value and 2 orders of magnitude lower than the predicted values of CoFe/MgO/CoFe junctions. The physics of this more realistic TMR value is the change in symmetry from C-4v of MgO to C-2v of kotoite. Such symmetry reduction induces scattering and weakens the tunneling transmission of the Delta(1)-like Bloch states. Our calculations also reveal that the tunneling transmission is sensitive to the electrode/spacer interfacial chemical bonding. Residual boron, localized at the interface due to insufficient annealing temperature, can further reduce the TMR. DOI: 10.1103/PhysRevB.87.014114
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页数：6
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