Magnon-assisted transport and thermopower in ferromagnet-normal metal tunnel junctions

Abstract

We develop a theoretical model of magnon-assisted transport in a mesoscopic tunnel junction between a ferromagnetic metal and a normal (non-magnetic) metal. The current response to a bias voltage is dominated by the contribution of elastic processes rather than magnon-assisted processes and the degree of spin polarization of the current, parameterized by a function $P({\Pi }_{\uparrow (\downarrow )},{\Pi }_N)$, $0\le P\le 1$, depends on the relative sizes of the majority ${\Pi }_{\uparrow }$ and minority ${\Pi }_{\downarrow }$ band Fermi surface in the ferromagnet and of the Fermi surface of the normal metal ${\Pi }_N$. On the other hand, magnon-assisted tunneling gives the dominant contribution to the current response to a temperature difference across the junction. The resulting thermopower is large, $S\sim -(k_B/e)(k_{B}T/{\omega }_D{)}^{3/2}P({\Pi }_{\uparrow (\downarrow )},{\Pi }_N)$, where the temperature dependent factor $(k_{B}T/{\omega }_D{)}^{3/2}$ reflects the fractional change in the net magnetization of the ferromagnet due to thermal magnons at temperature $T$ (Bloch's $T^{3/2}$ law) and ${\omega }_D$ is the magnon Debye energy.

arXiv comment7 pages, 2 eps figures

References in corpus (9)

• Random-Matrix Theory of Quantum Transport
• Basic obstacle for electrical spin-injection from a ferromagnetic metal into a diffusive semiconductor
• Theory of electrical spin injection: Tunnel contacts as a solution of the conductivity mismatch problem
• Spin flip scattering in magnetic junctions
• Assisted Tunneling in Ferromagnetic Junctions and Half-Metallic Oxides
• Giant magnetothermopower of magnon-assisted transport in ferromagnetic tunnel junctions
• Subgap transport in ferromagnet-superconductor junctions due to magnon-assisted Andreev reflection
• Magnetothermopower and magnon-assisted transport in ferromagnetic tunnel junctions
• Magnon-assisted Andreev reflection in a ferromagnet-superconductor junction

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