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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 20.73: Poster

Tuesday, March 28, 2006, 15:15–19:15, P1

Effect of Rare Earth Dopands in Permalloy Films and Multilayers — •Georg Woltersdorf¹, Jan-Ulrich Thiele², Manfred Schabes², Gereon Meyer ³, Matthias Kißling¹, Michael Binder¹, and Christian Back¹ — ¹Universität Regensburg, Institut für Experimentelle und Angewandte Physik — ²Hitatchi Global Storage Technologies — ³Stanford University, Department of Physics

We investigated the influence of rare earth dopands on the magnetic relaxation. In our experiments Permalloy (Ni₈₁Fe₁₉) films were doped with various concentrations of the rare earth ions Dy, Ho, and Tb. The magnetization dynamics of these films was studied using ferromagnetic resonance (FMR) and time resolved magneto optic Kerr effect (TR-MOKE) in a frequency range from 1 to 35 GHz. In agreement with earlier work [1] we find that the rare earth doping of Permalloy leads to a large increase of the damping parameter α. Our measurements can be well described using the Gilbert damping term in the equation of motion. This strongly suggests that the increased damping is due to an increased rate of transfer of angular momentum from the spin system to the lattice.

In addition, we studied a series of samples where the doped Py layer was exchange coupled to a ferromagnetic layer without rare earth doping. In such samples the doped layer acts as an additional drain for the angular momentum and leads to a faster relaxation of the magnetization dynamics of the undoped layer.
W. Bailey et al. IEEE Trans. Mag. 37, 1749(2001)