Ferromagnetic resonance study of sputtered Co|Ni multilayers

J-M. L. Beaujour; W. Chen; K. Krycka; C-C. Kao; J. Z. Sun; A. D. Kent

doi:10.1140/epjb/e2007-00071-1

paper

Ferromagnetic resonance study of sputtered Co|Ni multilayers

arXiv:cond-mat/0611027 · doi:10.1140/epjb/e2007-00071-1

Abstract

We report on room temperature ferromagnetic resonance (FMR) studies of [ $t$ Co $∣2 t$ Ni] $\times$ N sputtered films, where $0.1 \leq t \leq 0.6$ nm. Two series of films were investigated: films with same number of Co $∣$ Ni bilayer repeats (N=12), and samples in which the overall magnetic layer thickness is kept constant at 3.6 nm (N=1.2/ $t$ ). The FMR measurements were conducted with a high frequency broadband coplanar waveguide up to 50 GHz using a flip-chip method. The resonance field and the full width at half maximum were measured as a function of frequency for the field in-plane and field normal to the plane, and as a function of angle to the plane for several frequencies. For both sets of films, we find evidence for the presence of first and second order anisotropy constants, $K_{1}$ and $K_{2}$ . The anisotropy constants are strongly dependent on the thickness $t$ , and to a lesser extent on the total thickness of the magnetic multilayer. The Landé g-factor increases with decreasing $t$ and is practically independent of the multilayer thickness. The magnetic damping parameter $α$ , estimated from the linear dependence of the linewidth, $△ H$ , on frequency, in the field in-plane geometry, increases with decreasing $t$ . This behaviour is attributed to an enhancement of spin-orbit interactions with $t$ decreasing and in thinner films, to a spin-pumping contribution to the damping.

18 pages, 13 figures

Ferromagnetic resonance study of sputtered Co|Ni multilayers

Abstract

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