Magnetic relaxation in metallic films: Single and multilayer structures

Abstract

The intrinsic magnetic relaxations in metallic films will be discussed. It will be shown that the intrinsic damping mechanism in metals is caused by incoherent scattering of itinerant electron-hole pair excitations by phonons and magnons. Berger ͓L. Berger, Phys. Rev. B 54, 9353 ͑1996͔͒ showed that the interaction between spin waves and itinerant electrons in multilayers can lead to interface Gilbert damping. Ferromagnetic resonance ͑FMR͒ studies were carried out using magnetic single and double layer films. The FMR linewidth of the Fe films in the double layer structures was found to always be larger than the FMR linewidth measured for the single Fe films having the same thickness. The increase in the FMR linewidth scaled inversely with the film thickness, and was found to be linearly dependent on the microwave frequency. These results are in agreement with Berger's predictions.

Role of dynamic exchange coupling in magnetic relaxations of metallic multilayer films (invited)

“…2,26,27 The in-plane ferromagnetic resonance ͑FMR͒ experiments were carried out using 10, 24, 36, and 72 GHz systems. 3 Single Fe ultrathin films with thicknesses of 8,11,16,21, and 31 monolayers ͑MLs͒ were grown directly on GaAs͑001͒.…”

Semiclassical theory of spin transport in magnetic multilayers

“…The internal magnetic field is treated by employing Maxwell's equations. A precessing magnetization in FM creates a spin current which is described by spin pumping proposed by Tserkovnyak et In our recent ferromagnetic resonance ͑FMR͒ studies [1][2][3][4] it was shown that the transfer of the spin momentum across ferromagnetic ͑FM͒/normal metal ͑NM͒ interfaces can result in nonlocal interface Gilbert damping GЈ. The generation of spin momentum in magnetic ultrathin films was theoretically described by Tserkovnyak et al 5 and the effect was called ''spin pumping.''…”

“…The presence of a second magnetic layer creates a spin sink. 3,4,6,7 The combination of spin pump and spin sink in the ballistic limit leads to an additional interface Gilbert damping. In this article we extend the spin pump and spin sink mechanisms to the nonballistic electron transport which includes a full treatment of the Landau-Lifshitz ͑LL͒ equation of motion in FM and diffusion equation in NM and Maxwell's equations accounting for a finite penetration of the rf fields.…”

Temperature dependence of Gilbert damping in manganite/normal metal heterostructure

“…The Gilbert damping α is the times scale for relaxation which can take place in two different ways: either the spin angular momentum is transferred to non-magnetic degrees of freedom, which is called direct, homogenous damping; or the spin angular momentum is transferred to other magnetic degrees of freedom such as spin waves, impurity, which is called indirect Inhomogeneous dampingm Significant relaxation processes in thin ferromagnetic films [12] are spin-orbit relaxation damping, two-magnon scattering and eddy current damping.…”