Symmetry selective resonances in Fe-MgO-ZnO-MgO-Fe

Abstract We propose the physics of symmetry-selective resonance of the ∆1 states in the Fe/MgO/ZnO/MgO/Fe heterostructures, that offers a broad landscape to design magnetic tun- nel junctions (MTJs). These MTJs yield a towering tunnel magnetoresistance (TMR) upto 3.5×104% with the resistance area (RA) product dipping down till a minimum of 0.05Ω-µm2 , while maintaining a nearly perfect (99%) spin polarization. Our predictions are based on the self-consistent coupling of the non-equilibrium Green’s function(NEGF) with the density func- tional theory(DFT). We also present the charge current, spin current and TMR of a prototype(p) Fe/MgO(3-layer(l))/ZnO(3l)/MgO(3l)/Fe-MTJ(abbreviated as p-∆R1 -MTJ), which provides a pro- nounced advancement in the TMR(1.3×104%), RA product(0.45Ω-µm2 ) and spin polarization(99%) over its Fe/MgO(6l)/Fe-based counterpart(TMR ≈ 3.4 × 103%, RA product≈ 23Ω-µm2 ). A marked improvement in RA product with 99% spin polarization while maintaining 4 times higher TMR in p- ∆R1 -MTJ over the regular(r)-MTJ is a strong indicator of a momentous improvement in spin-transfer torque(STT). Using the non-equilibrium finite bias characteristics, we estimate 54-fold improvement in STT-switching energy of the p-∆R1 -MTJ over r-MTJ. We substantiate our findings by combin- ing the transmission eigenchannel analysis, spectral density, and Fe-contact band structure in the p-∆R1 -MTJ, thereby elucidating the physics of symmetry-selective resonances.