Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 51: Transport: Nanoelectronics II - Spintronics and Magnetotransport (jointly with HL and MA)

TT 51.7: Talk

Friday, March 30, 2012, 11:15–11:30, BH 243

Investigation of magnetic point contacts irradiated by microwave and THz radiation — •Stefan Egle, Torsten Pietsch, and Elke Scheer — Department of Physics, University of Konstanz

The growing field of spintronics became one of the most intensively studied topics in modern solid-state physics. The possibility not only exploiting the charge of an electron, but also its spin (or magnetic moment), offers the possibility to explore various interesting effects. In this talk, we investigate magnetic point contacts and heterostructures, where a ferromagnet (F) acts as a spin polarizer, injecting hot electrons into a non-magnetic metal (N) or a diluted ferromagnet (f). Thereby, an external magnetic field in case of N is used to generate a Zeeman-splitting between spin-up and spin-down electrons. In case of F/f-contacts, this energy splitting ΔE is given by the exchange energy of f. These energies correspond to electromagnetic frequencies in the GHz (N) and THz regime (f). The highly non-equilibrium spin-population of F is then used to create a spin inversion in N or f, leading to a spin-flip photon emission. By matching the resonant condition hν=ΔE and using an external source in the microwave and THz range, theory predicts an induced spin lasing effect in N/f. Presently, we investigate the influence of the external irradiation on the electronic resistance via transport spectroscopy. In particular, we will present our measurements on the magnetotransport properties, studying the complex interplay between the crucial parameters, namely magnetization, current density and geometry of the point contacts. The results illustrate that a successful spin-population inversion can be detected.