Large magnetoresistance in bcc Co/MgO/Co and FeCo/MgO/FeCo tunnel junctions

By X.-G. Zhang, W. Butler. 2004

305 citations recorded by the source corpus.

By use of first-principles electronic structure calculations, we predict that the magnetoresistance of the bcc $\mathrm{Co}(100)∕\mathrm{Mg}\mathrm{O}(100)∕\mathrm{bcc}\mathrm{Co}(100)$ and $\mathrm{Fe}\mathrm{Co}(100)∕\mathrm{Mg}\mathrm{O}(100)∕\mathrm{Fe}\mathrm{Co}(100)$ tunneling junctions can be several times larger than the very large magnetoresistance predicted for the $\mathrm{Fe}(100)∕\mathrm{Mg}\mathrm{O}(100)∕\mathrm{Fe}(100)$ system. The origin of this large magnetoresistance can be understood by considering the electrons at the Fermi energy traveling perpendicular to the interfaces. For the minority spins there is no state with ${\ensuremath{\Delta}}_{1}$ symmetry whereas for the majority spins there is only a ${\ensuremath{\Delta}}_{1}$ state. The ${\ensuremath{\Delta}}_{1}$ state decays much more slowly than the other states within the MgO barrier. In the absence of scattering which breaks the conservation of momentum parallel to the interfaces, the electrons traveling perpendicular to the interfaces undergo total reflection if the moments of the electrodes are antiparallel. These arguments apply equally well to systems with other well ordered tunnel barriers and for which the most slowly decaying complex energy band in the barrier has ${\ensuremath{\Delta}}_{1}$ symmetry. Examples include systems with (100) layers constructed from Fe, bcc Co, or bcc FeCo electrodes and Ge, GaAs, or ZnSe barriers.

Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics

View Paper: https://www.semanticscholar.org/paper/2b1f3a665c82e825738301417b78a834ac0c5a28

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Citations in the corpus

Spin-transfer effects in nanoscale magnetic tunnel junctions (2004, background): “This includes CoFe, CoFeB, and even bcc Co (which is ordinarily hcp or fcc) [31].”
Spin-torque building blocks. (2014, background): “The resistance variations are today limited to TMR ratios of about 100 %, but the theoretical limit for RAP/RP is much higher, close to 300 [47].”
Nobel Lecture: Origin, development, and future of spintronics (2008, background): “In such MTJ, the single crystal barrier filters the symmetry of the wave functions of the tunneling electrons Mathon and Umerski, 1999; Mavropoulos et al., 2000; Zhang and Butler, 2004 , so that the TMR depends on the spin polarization of the electrodes for the selected symmetry.”
Oxide Spintronics (2007, background): “multiferroic materials [276] is circumvented by the emerging field of artificial multiferroics that combine ferroelectric and magnetic materials in the same heterostructure [73], [277].”
Magnetic Tunnel Junctions for Spintronic Memories and Beyond (2007, unknown): “Employing a double-barrier structure has also been shown effective in increasing ∆V [76].”
Tunnel Magnetoresistance Over 100% in MgO-Based Magnetic Tunnel Junction Films With Perpendicular Magnetic L1$_{0}$-FePt Electrodes (2008, unknown): “bcc-Fe(001), bcc-Co(001), and bcc-FeCo(001) electrodes [4], [5].”
Spin-polarised currents and magnetic domain walls (2005, background): “was predicted to have even greater scope for large TMR ratios than pure Fe electrodes [42].”