Dresden 2014 – scientific programme

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MA: Fachverband Magnetismus

MA 7: ThyssenKrupp Electrical Steel Dissertationspreis der AG Magnetismus

MA 7.2: Talk

Monday, March 31, 2014, 12:50–13:10, HSZ 04

Spin waves in thin films — •Rajeswari Jayaraman — Peter Grünberg Institut, Forschungszentrum Jülich

Wave packets of spin waves o_er the unique capability to transport quantum information without the transport of charge or mass. In this context, large wave-vector spin waves are of particular interest as they admit spin localization within a few nanometers. By using our recently developed electron energy loss spectrometer, we could study such spin waves in ultra-thin films with an unprecedented energy resolution of 4 meV. Due to the high energy resolution we discovered standing spin waves in addition to the well known surface spin waves. We have performed a systematic study of these standing spin waves as function of layer thickness for fcc Co films deposited on Cu(100). By comparing the dispersion of the standing mode and the surface mode dispersion to theory, we obtain information on the layer dependence of the exchange coupling constants.

Due to elaborate electron optical calculations, our spectrometer is calibrated in terms of the accepted solid angle and the transmission probability. Exploiting this fact, we convert the measured intensities into probabilities of spin wave excitations. The scattering probability as function of energy exhibits a peak around 7 eV for fcc cobalt and 3 eV for hcp cobalt. For electron energies beyond 10 eV the scattering probability becomes immeasurably small which is in stark contrast to theoretical predictions.