Zhaoqiang Bai, Lei Shen, Yongqing Cai, Qingyun Wu, Minggang Zeng, Guchang Han, Yuan Ping Feng
There are two significant challenges, the thermal stability (both structure and magnetization) and spin polarization (both material and transport), for the development of magnetic tunnel junction (MTJ)-based non-volatile magnetoresistive random access memory (MRAM) currently. Using first principles calculations, we study the thermal stability of the interfacial structure and magnetization, as well as the interfacial and transport spin polarization of Co2FeAl (CFA)/MgO/Co2FeAl (001) MTJs. It is found that the architecture of FeAl-O is the most thermally stable interfacial structure. Investigation on the interfacial magnetization demonstrates a perpendicular-anisotropy at the CFA/MgO interface, which is attributed to the hybridization of the Fe-dz2 and O-pz orbitals. This perpendicular magnetocrystalline anisotropy (MCA) provides the magnetic thermal stability, which can be further tuned using an external electric field via the magnetoelectric effect. Based on the spin polarization calculations, the half-metallicity of CFA electrodes can be quickly recovered within only a few atomic layers back away from the interface to the bulk, indicating the reserve of high spin polarization in the ultra-thin CFA ferroelectric layer. Compared with CoFe/MgO/CoFe and FePt/MgO/FePt MTJs, our transport calculations show that CFA/MgO/CFA MTJs have better MR properties (MR ratio and {\Delta}RA). Our systematical study on CFA/MgO/CFA junctions provides a useful guide for the experimental development of high-performance MTJs, and then non-volatile MRAM.
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http://arxiv.org/abs/1303.3473
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