Origin of The Enhanced Perpendicular Anisotropy of Dual Barriermagnetic Tunnel Junction
CoFeB/MgO based magnetic tunnel junction (MTJ) was highlighted for its great potential on magnetic random access memory (MRAM) technology owing to tunable perpendicular magnetic anisotropy (PMA). We found significant enhancement of PMA by inserting additional MgO into the MTJ structure. The dual-MgO structure appeared to favor B diffusion but prevent capping-layer (Ta) penetration across the interface. This suppressed the dead-layer effect but promoted PMA as well as spin-polarization level, due to improved CoFeB/MgO crystallinity compared to the single-MgO structure. For the single-MgO, reducing CoFeB thickness promoted PMA but scarified spin-polarization inevitably. However, the dual-MgO could restore the spin-polarization by preferentially populating spin electrons into Fe/Co minority states. The dual-MgO displayed exclusive thickness-controlled natures in PMA, spin-polarization, dead-layer, and spin-dependent transport properties. These findings suggest that the dual-MgO structure is promising for tailoring the CoFeB/MgO’s physical properties in MRAM technology.
Keywords- Magnetic tunnel junction, magnetic random access memory