TY - JOUR
T1 - Dependence on annealing temperatures of tunneling spectra in high-resistance CoFeB/MgO/CoFeB magnetic tunnel junctions
AU - Matsumoto, Rie
AU - Nishioka, Shingo
AU - Mizuguchi, Masaki
AU - Shiraishi, Masashi
AU - Maehara, Hiroki
AU - Tsunekawa, Koji
AU - Djayaprawira, David D.
AU - Watanabe, Naoki
AU - Otani, Yuichi
AU - Nagahama, Taro
AU - Fukushima, Akio
AU - Kubota, Hitoshi
AU - Yuasa, Shinji
AU - Suzuki, Yoshishige
N1 - Funding Information:
This work was supported by a Grant-in-Aid for Scientific Research (A) from the Japan Society for the Promotion of Science. We would like to thank Ms. M. Yamamoto for her help with micro-fabricating our samples.
PY - 2007/9
Y1 - 2007/9
N2 - 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 Δ5 and Δ2′ 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 Δ1 states in MgO(001) or bcc CoFeB(001).
AB - 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 Δ5 and Δ2′ 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 Δ1 states in MgO(001) or bcc CoFeB(001).
KW - A. Magnetic films and multilayers
KW - D. Electronic band structure
KW - D. Electronic transport
KW - D. Tunneling
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U2 - 10.1016/j.ssc.2007.07.001
DO - 10.1016/j.ssc.2007.07.001
M3 - Article
AN - SCOPUS:34548040393
SN - 0038-1098
VL - 143
SP - 574
EP - 578
JO - Solid State Communications
JF - Solid State Communications
IS - 11-12
ER -