Theory for Tunnel Magnetoresistance Oscillation

Abstract

The universal oscillation of the tunnel magnetoresistance (TMR) ratio as a function of the insulating barrier thickness in crystalline magnetic tunnel junctions (MTJs) is a long-standing unsolved problem in condensed matter physics. To explain this, we here introduce a superposition of wave functions with opposite spins and different Fermi momenta, based on the fact that spin-flip scattering near the interface provides a hybridization between majority- and minority-spin states. In a typical Fe/MgO/Fe MTJ, we solve the tunneling problem and show that the TMR ratio oscillates with a period of $\sim 3$Å by varying the MgO thickness, consistent with previous and present experimental observations.

12 pages, 10 figures

References in corpus (10)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Slater-Pauling Behavior of the Half-Ferromagnetic Full-Heusler Alloys
• Ballistic conductance of magnetic Co and Ni nanowires with ultrasoft pseudo-potentials
• Half-metallic ferromagnets for magnetic tunnel junctions
• A first-principles study of tunneling magnetoresistance in Fe/MgAl2O4/Fe(001) magnetic tunnel junctions
• Exceeding 400% tunnel magnetoresistance at room temperature in epitaxial Fe/MgO/Fe(001) spin-valve-type magnetic tunnel junctions
• Bias voltage effects on tunneling magnetoresistance in Fe/MgAl${}_2$O${}_4$/Fe(001) junctions: Comparative study with Fe/MgO/Fe(001) junctions
• Enhanced Tunnel magnetoresistance in Fe/Mg4Al-Ox/Fe(001) Magnetic Tunnel Junctions
• Crucial role of interfacial $s$-$d$ exchange interaction in the temperature dependence of tunnel magnetoresistance
• First-principles study on magnetic tunneling junctions with semiconducting CuInSe${}_2$ and CuGaSe${}_2$ barriers