Dresden 2006 – wissenschaftliches Programm
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MA: Magnetismus
MA 20: Poster: Films(1-36) Transp(37-56) Ex.Bias(57-67) Spindyn(68-80) Micromag(81-95) Particle(96-109) Imag.+Surface(110-113) Spinelectr(114-122) Theory+Micromag(123-131) Spinstr+Aniso(132-142) MagMat(143-156) Meas(157,158) MolMag+Kondo(159-162) Postdead(163-)
MA 20.72: Poster
Dienstag, 28. März 2006, 15:15–19:15, P1
Laser induced magnetization dynamics: precession modes and damping parameter — •J. Walowski1, M. Djordjevic1, G. Eilers1, A. Parge1, M. Münzenberg1, and J. S. Moodera2 — 1IV. Phys. Institute, University of Goettingen, Germany — 2Francis Bitter Magnet Laboratory, MIT, Cambridge, USA
The development of spintronics requires coherent optical control of magnetization in thin ferromagnetic films on sub ns timescale. Time resolved magneto-optical Kerr effect is used to follow the magnetization dynamics upon ultrafast laser excitation with 50 fs resolution. We will present a detailed study of the dominant magnetic relaxation modes and the energy dissipation processes through both intrinsic and non-local Gilbert damping in thin Ni films. We were able to trigger the magnetization dynamics with a laser induced change in the anisotropy field and control the precession modes with the amplitude and the orientation of the external field, as well as with the pump laser fluence. The frequency spectrum are in the ranges from 1.5 GHz up to 13 GHz. They describe the characteristic homogeneous mode as well as the intrinsic standing spin wave modes. The corresponding intrinsic Gilbert damping parameter has been found to be dependent on the precession mode, taking values from α=0.05 up to α=0.25. The non-local Gilbert damping, due to emission of spin waves, is investigated at Ni/NM double layers (NM=Cu, Al, Ti, Cr, Pd, Dy). Enhancement in the Gilbert damping parameter of more than one order of magnitude is observed for materials with strong spin-orbit coupling and we present for the first time a coherent study.