Charge and Spin Transport in Magnetic Tunnel Junctions: Microscopic Theory

Abstract

We study the charge and spin currents passing through a magnetic tunnel junction (MTJ) on the basis of a tight-binding model. The currents are evaluated perturbatively with respect to the tunnel Hamiltonian. The charge current has the form $A[{\mathbf{M}}_1(t)\times {\dot{\mathbf{M}}}_1(t)]\cdot {\mathbf{M}}_2+B{\dot{\mathbf{M}}}_1(t)\cdot {\mathbf{M}}_2$, where ${\mathbf{M}}_1(t)$ and ${\mathbf{M}}_2$ denote the directions of the magnetization in the free layer and fixed layer, respectively. The constant $A$ vanishes when one or both layers are insulators, {while the constant $B$ disappears when both layers are insulators or the same ferromagnets.} The first term in the expression for charge current represents dissipation driven by the effective electric field induced by the dynamic magnetization. In addition, from an investigation of the spin current, we obtain the microscopic expression for the enhanced Gilbert damping constant $\Delta \alpha$. We show that $\Delta \alpha$ is proportional to the tunnel conductance and depends on the bias voltage.

13 pages, 1 figure, accepted for publication in Journal of the Physical Society of Japan

References in corpus (7)

• Microscopic Calculation of Spin Torques in Disordered Ferromagnets
• Tunnel barrier enhanced voltage signals generated by magnetization precession of a single ferromagnetic layer
• Diffusive versus local spin currents in dynamic spin pumping systems
• Spin and charge pumping in magnetic tunnel junctions with precessing magnetization: A nonequilibrium Green function approach
• Charge and Spin Currents Generated by Dynamical Spins
• Tunnel-barrier-enhanced dc voltage signals induced by magnetization dynamics in magnetic tunnel junctions
• Charge pumping in magnetic tunnel junctions: Scattering theory

Cited by in corpus (1)

• Tunable Spin Seebeck Diode with Magnonic Spin Tunneling Junction