Regensburg 2010 – scientific programme

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MA: Fachverband Magnetismus

MA 28: Spin-dependent Transport Phenomena

MA 28.12: Talk

Thursday, March 25, 2010, 18:15–18:30, H3

Spin dependent transport of hot electrons in bcc Fe(100) and bcc Fe₃₄Co₆₆(100) — •Emanuel Heindl, Johann Vancea, and Christian H. Back — Department of Physics, University of Regensburg, 93040 Regensburg, Germany

We investigate hot electron spin filtering in thin bcc Fe(100) and bcc Fe₃₄Co₆₆(100) layers using Ballistic Electron Emission Microscopy. An STM tip is used as a tunable constant current source of hot electrons being injected into single crystalline metallic spin valve structures. The subsequent ballistic hot electron transport is recorded and separated from thermalized electron transport by means of a metal semiconductor junction whose Schottky barrier acts as a spectrometer. Electron transport is carried out with the main transport axis along the [100]-axis of the ferromagnetic layers at electron energies between 1 eV and 2.5 eV above the Fermi level. Parallel and antiparallel magnetization configurations of the spin valve are readily adjustable with an external magnetic field as revealed by Kerr effect and magnetocurrent measurements.

When the Fe₃₄Co₆₆ electrode is replaced by Fe the spin contrast drops by more than a factor of 5 in the studied energy interval. We interpret this observation to the spin asymmetry of unoccupied states and to the electron velocity being distinct for majority and minority spins. By cooling down from room temperature to 130 K ballistic currents become significantly enhanced for both materials in the parallel and the antiparallel magnetization configuration, while hot electron spin polarization is enhanced for Fe₃₄Co₆₆, only.