Observation and modelling of ferromagnetic contact-induced spin relaxation in Hanle spin precession measurements

Abstract

In the non-local spin valve (NLSV) geometry, four-terminal electrical Hanle effect measurements have the potential to provide a particularly simple determination of the lifetime ( ) and diffusion length ( ) of spins injected into non-magnetic materials. Recent work, however, has demonstrated that traditional models typically used to fit such data provide an inaccurate measurement of in ferromagnet/nonmagnetic metal (FM/N) devices with low interface resistance, particularly when the separation of the source and detector contacts is small. In the transparent limit, this shortcoming is due to the backdiffusion and subsequent relaxation of spins within the FM contacts, which is not properly accounted for in standard models of the Hanle effect. Here we have used the separation dependence of the spin accumulation signal in NLSVs with multiple FM/N combinations, and interfaces in the diffusive limit, to determine in traditional spin valve measurements. We then compare these results to Hanle measurements as analyzed using models that either include or exclude spin sinking. We demonstrate that differences between the spin valve and Hanle measurements of can be quantitatively modelled, provided that both the FM contact-induced isotropic spin-sinking and the full three-dimensional geometry of the devices, which is particularly important at small contact separations, are accounted for.We find, however, that considerable difficulties persist, in particular due to the sensitivity of fitting to the contact interface resistance and the FM contact magnetization rotation, in precisely determining with the Hanle technique alone, particularly at small contact separations. † Corresponding author: lao24@cam.ac.uk No's: 72.25.Ba, 72.25.Mk, 72.25.Rb PACS

Detection of the interfacial exchange field at a ferromagnetic insulator-nonmagnetic metal interface with pure spin currents

“…In comparison with EuS capped LSV devices, the devices grown on top of a EuS substrate show no significant d dependence in the low temperature regime. A possible explanation for the observed peak shifts to higher temperatures might originate from effects like spin back flow into Py and anisotropic spin absorption at the Py/Cu interfaces particularly when injector -detector distance d is comparable or shorter than spin diffusion length λ s of Cu [33][34][35]. We believe the anomalous low temperature behavior observed in our case does not originate from these effects, as the shift would show a pronounced dependence of the injector-detector distance d.…”

Synthetic Rashba spin–orbit system using a silicon metal-oxide semiconductor

“…2(a)-2(d). The signals were nicely reproduced by a conventional one-dimensional fitting function 28,29 , where the spin lifetime at  = 90°, i.e., s  P , under V g = 0 V was estimated to be 2.5 ± 0.1 ns, and the precessional motion of the spins dephases at B ex ~ 40 mT (see also Supplemental Information No. 1).…”

Magneto-Optical Trap Field Characterization with the Directional Hanle Effect

“…In 1924, Wilhelm Hanle presented a theory explaining the depolarization of light scattered by an atomic vapor in a magnetic field. This effect, known as the Hanle effect, has been used to determine atomic state lifetimes 1 , to measure magnetic fields [2][3][4] , and to measure phenomena related to magnetic fields 5,6 . Other manifestations associated with the Hanle effect include level-crossing spectroscopy 7,8 , and a "mechanical" Hanle effect 9 .…”