Author/Authors :
Matsumoto، نويسنده , , Rie and Nishioka، نويسنده , , Shingo and Mizuguchi، نويسنده , , Masaki and Shiraishi، نويسنده , , Masashi and Maehara، نويسنده , , Hiroki and Tsunekawa، نويسنده , , Koji and Djayaprawira، نويسنده , , David D. and Watanabe، نويسنده , , Naoki and Otani، نويسنده , , Yuichi and Nagahama، نويسنده , , Taro and Fukushima، نويسنده , , Akio and Kubota، نويسنده , , Hitoshi and Yuasa، نويسنده , , Shinji and Suzuki، نويسنده , , Yoshishige، نويسنده ,
Abstract :
We investigated the annealing temperature dependence of differential tunneling conductance spectra ( d I / d V 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 d I / d V 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 Δ 5 and Δ 2 ′ 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 Δ 1 states in MgO(001) or bcc CoFeB(001).
Keywords :
A. Magnetic films and multilayers , D. Electronic band structure , D. Electronic transport , D. Tunneling
