Enhanced electron-magnon scattering in ferromagnetic thin films and the breakdown of the Mott two-current model

Abstract

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Electron-magnon spin-flip scattering in thin films was studied by investigating the thickness dependence of the anisotropic magnetoresistance (AMR) effect and spin-wave stiffness. The absolute resistivity change due to the AMR effect ( ρ) in Ni, Ni:V, and Ni:Cr doped films reduced with film thickness. This loss of AMR is due to enhanced spin-flip scattering, dropping at the same thickness irrespective of dopant. The spin-wave stiffness reduced at the same thickness, confirming enhanced electron-magnon spin-flip scattering. The AMR ratio was fitted with a simple model, in which thickness dependence was included in a spin mixing resistivity term. This analysis gives insight into the fundamental contribution of magnon scattering to the resistivity in thin films, which ultimately has relevance to spin coherence in spintronic devices.

Interfacial contribution to thickness dependent in-plane anisotropic magnetoresistance

“…1(c). The decrease in both ∆ρ and the AMR ratio with decreasing FM film thickness is seen in single films, 5,15 and multilayers 3 and is, in general, not entirely due to current shunting through under/overlayers at smaller FM thicknesses, 16 contrary to the suggestion in Ref. 4.…”

“…The crossover at low thickness can not be explained due to magnon scattering. 5 Liu et al 3 studied AMR in multilayers of Ta/(Pt)/NiFe/(Pt)/Ta and observed an enhancement similar to that shown here for Co/Ir in Fig. 1(c), and attributed to interfacial SOI.…”

“…5,15 Recently, an interfacial contribution to the out-of-plane AMR, dubbed anisotropic interfacial magnetoresistance, which manifests as a small thickness-dependent difference between the AMR for magnetization rotated in-plane and out-of-plane has been found in Pt/Co/Pt trilayers 4 multilayers. 16 This anisotropic interface magnetoresistance has since been suggested to be explained in terms of a 'hybrid' magnetoresistance as the result of interfacial proximity polarisation of Pt or Pd adjacent to a FM.…”

“…[3][4][5] In ferromagnetic (FM) metals AMR is considered to be a consequence of the spin-orbit interaction (SOI) within the bulk and is manifest as a dependence of the electrical resistivity, ρ, on the angle θ between current density J and magnetization M. In polycrystalline FM transition-metals it has been shown 2,6 that a simple variation of ρ with θ goes as ρ (θ) = ρ ⊥ + ∆ρcos 2 θ, where ρ ⊥ is the transverse (θ = π/2) resistivity, and ∆ρ is the difference between longitudinal (ρ ∥ = ρ (θ = 0)) and transverse resistivities, ∆ρ = ρ ∥ − ρ ⊥ . Here the AMR ratio is defined as; AMR = ∆ρ/ρ ⊥ , as both ρ ∥ and ρ ⊥ correspond to well-defined saturated magnetization states.…”

Evolution of damping in ferromagnetic/nonmagnetic thin film bilayers as a function of nonmagnetic layer thickness

“…However, the effect of spin pumping should be very limited over the studied thickness range of Pt, as it is comparable or below the spin-diffusion length, λ sd [12,[33][34][35][36]. Hence, d-d hybridization mainly contributes to the intrinsic enhancement of the damping.…”