Dependence on annealing temperatures of tunneling spectra in high-resistance CoFeB/MgO/CoFeB magnetic tunnel junctions
- 作者：Rie Matsumoto ; Shingo Nishioka ; Masaki Mizuguchi ; Masashi Shiraishi ; Hiroki Maehara ; Koji Tsunekawa ; David D. Djayaprawira ; Naoki Watanabe ; Yuichi Otani ; Taro Nagahama ; Akio Fukushima ; Hitoshi Kubota
- 关键词：A. Magnetic films and multilayers ; D. Electronic band structure ; D. Electronic transport ; D. Tunneling
- 刊名：Solid State Communications
- 出版年：2007
- 期刊代码：101_00381098
- 类别：ms
- 出版时间：September 2007
- 卷：143
- 期：11-12
- 页码：574-578
- 文件大小：531 K
摘要
We investigated the annealing temperature dependence of differential tunneling conductance spectra (
as a function of V) in CoFeB/textured MgO(001)/CoFeB magnetic tunnel junctions (MTJs) that exhibit the giant tunneling magnetoresistance (TMR) effect at room temperature. The spectra were strongly affected by annealing the MTJs. A reduction in 
at around ±300 mV was observed only in annealed MTJs in which the CoFeB electrodes were crystallized in a bcc(001) structure. Because the reduction in conductance was observed in both MTJs that have a 1.8-nm-thick MgO barrier and MTJs that have a 3.2-nm-thick MgO barrier, we concluded that 
and 
evanescent states, which rapidly decay in the MgO tunneling barrier, are not the cause of the reduction in conductance. We believe the cause of the reduction is either the electronic structure of the interfaces between MgO(001)/bcc CoFeB(001) after annealing or a particular feature of 
states in MgO(001) or bcc CoFeB(001).