Theory of the ac spin-valve effect

TL;DR

This paper models the ac spin-valve effect in symmetric ferromagnet/normal metal/ferromagnet junctions, revealing oscillatory magnetoresistance behavior that can help determine spin transport parameters without magnetic fields.

Contribution

It provides a theoretical analysis of the ac spin-valve effect using the drift-diffusion model, predicting oscillatory and Lorentzian behaviors in magnetoresistance.

Findings

Oscillatory ac magnetoresistance in wide junctions

Lorentzian line shape in thin tunnel junctions

Potential method to measure spin parameters without magnetic fields

Abstract

The spin-valve complex magnetoimpedance of symmetric ferromagnet/normal metal/ferromagnet junctions is investigated within the drift-diffusion (standard) model of spin injection. The ac magnetoresistance---the real part difference of the impedances of the parallel and antiparallel magnetization configurations---exhibits an overall damped oscillatory behavior, as an interplay of the diffusion and spin relaxation times. In wide junctions the ac magnetoresistance oscillates between positive and negative values, reflecting resonant amplification and depletion of the spin accumulation, while the line shape for thin tunnel junctions is predicted to be purely Lorentzian. The ac spin-valve effect could be a technique to extract spin transport and spin relaxation parameters in the absence of a magnetic field and for a fixed sample size.