| AVS 62nd International Symposium & Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuP |
| Session: | Electronic Materials and Processing Poster Session |
| Presenter: | Masaaki Araidai, Nagoya University, Japan |
| Authors: | M. Araidai, Nagoya University, Japan T. Yamamoto, Tokyo University of Science, Japan K. Shiraishi, Nagoya University, Japan |
| Correspondent: | Click to Email |
Investigation of magnetic tunnel junction (MTJ) is a key issue for the development of advanced magnetoresistive random access memories (MRAMs). MTJs consist of two metal ferromagnets, thick magnetization-fixed and thin magnetization-free layers, separated by a thin insulator, and they exhibit two resistances, low or high, depending on the relative direction of the magnetizations of fixed and free layers, parallel (P) or antiparallel (AP) configuration. The simplest way to reverse the magnetization of free layer is switching by external magnetic fields. However, absolute currents required for the magnetic-field switching do not scale with reducing the junction size. At present, current-induced magnetization switching (CIMS) proposed by Slonczewski [1] and Berger [2] is drawing attention as the most promising candidate for a mechanism of magnetization reversal of free layer, owing to the scalability of CIMS [3]. Although CIMS has been successfully applied to the operation of MRAM, it has not been sufficiently understood yet.
In this work, we investigated electron scattering processes in CIMS of a MTJ by the non-equilibrium Green's function technique coupled with the density-functional theory [4]. We employed a Fe/MgO/Fe MTJ sandwiched between ferromagnetic Fe and paramagnetic Ta electrodes, as a typical MTJ model. The current-voltage characteristics indicated high tunnel magnetoresistance of the MTJ (about 600% at zero bias) and was highly antisymmetric with respect to the bias voltage, originating from the antisymmetric structure and the magnetization configuration. We found from the current density dependence of magnetization of the free layer that the switching from AP to P configuration could be realized by lower electrical power than P-to-AP case. From detailed analyses of the density of states subject to a finite bias voltage, we clarified that the asymmetric behavior originates from the difference in the electron scattering processes between switching directions.
[1] J. C. Slonczewski, J. Magn. Magn. Mater. 159, L1 (1996).
[2] L. Berger, Phys. Rev. B 54, 9353 (1996).
[3] Ikeda et al., IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 54, 991 (2007).
[4] M. Araidai, T. Yamamoto, and K. Shiraishi, Appl. Phys. Express 7, 045202 (2014).