Manifestation of two-channel nonlocal spin transport in the shapes of the Hanle curves

TL;DR

This paper investigates how two-channel nonlocal spin transport influences the shape of Hanle curves in coupled wires, revealing dependence on tunneling, diffusion, and geometry, with implications for spintronic device analysis.

Contribution

It introduces a detailed analysis of Hanle curve shapes in coupled wires, considering tunneling, geometry, and diffusive trajectories, advancing understanding of spin transport phenomena.

Findings

Hanle curve shapes depend on tunneling and diffusion parameters.

Differences in intra- and inter-wire Hanle curves reflect diffusive trajectory statistics.

Loop geometry influences Hanle curves through random walk statistics.

Abstract

Dynamics of charge-density fluctuations in a system of two tunnel-coupled wires contains two diffusion modes with dispersion iw=Dq^2 and iw =Dq^2+2/tau_t, where D is the diffusion coefficient and tau_t is the tunneling time between the wires. The dispersion of corresponding spin-density modes depends on magnetic field as a result of spin precession with Larmour frequency, w_L. The presence of two modes affects the shape of the Hanle curve describing the spin-dependent resistance, R, between ferromagnetic strips covering the non-magnetic wires. We demonstrate that the relative shapes of the R(w_L)-curves, one measured within the same wire and the other measured between the wires, depends on the ratio tau_t/tau_s, where tau_s is the spin-diffusion time. If the coupling between the wires is local, i.e. only at the point x=0, then the difference of the shapes of intra-wire and inter-wire Hanle curves reflects the difference in statistics of diffusive trajectories which "switch" or do not switch near x=0. When one of the coupled wires is bent into a loop with a radius, a, the shape of the Hanle curve reflects the statistics of random walks on the loop. This statistics is governed by the dimensionless parameter, a/(D tau_s)^(1/2).