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HL: Fachverband Halbleiterphysik

HL 40: Transport: Spintronics and magnetotransport (organized by TT)

HL 40.1: Vortrag

Dienstag, 1. April 2014, 09:30–09:45, BEY 81

Spin-population inversion in Co/Pd heterojunctions — •Torsten Pietsch, Stefan Egle, and Elke Scheer — Department of Physics, Universitätstraße 10, University of Konstanz, 78457 Konstanz, Germany

Herein, we investigate experimentally the magneto-transport properties of nanosized Co/Pd hetero contacts and show that a spin-population inversion can be created by resonantly exciting magnetic heterojunctions with high-frequency waves in the GHz and THz regime. Recently, spin-flip photoemission in such metallic, magnetic heterojunctions was predicted theoretically but has not been observed experimentally. When an external magnetic field is applied the Zeeman splitting in the normal metal lifts the spin-degeneracy. Under a large current bias, hot electrons from the ferromagnet can be injected into the upper Zeeman level, thus creating a spin-population inversion in the normal metal. This non-equilibrium spin-population inversion decays via spin-flip transitions, which results in the creation of magnons, scattering at magnetic impurities and, under certain circumstances, photoemission. In the later, case, the energy of the emitted photon corresponds to the Zeeman energy, which can be tuned by the external magnetic field; typical frequencies are in the range of 0.1GHz to 60GHz. By resonantly exciting the Co/Pd point contacts using an external RF source while monitoring the transport properties, we evaluate the parameter space, where a spin-population inversion can be created at the ferromagnet-normal metal interface.