Effect of the interface resistance in non-local Hanle measurements

Abstract

We use lateral spin valves with varying interface resistance to measure non-local Hanle effect in order to extract the spin-diffusion length of the non-magnetic channel. A general expression that describes spin injection and transport, taking into account the influence of the interface resistance, is used to fit our results. Whereas the fitted spin-diffusion length value is in agreement with the one obtained from standard non-local measurements in the case of a finite interface resistance, in the case of transparent contacts a clear disagreement is observed. The use of a corrected expression, recently proposed to account for the anisotropy of the spin absorption at the ferromagnetic electrodes, still yields a deviation of the fitted spin-diffusion length which increases for shorter channel distances. This deviation shows how sensitive the non-local Hanle fittings are, evidencing the complexity of obtaining spin transport information from such type of measurements.

Anisotropic Hanle line shape via magnetothermoelectric phenomena

“…2(c) and (d)). These Hanle data were fitted with an analytical expression obtained by solving the Bloch equation considering spin precession, diffusion and relaxation for transparent contacts [13,21] and taking into account the out-of-plane rotation of the Py magnetization [3]. From the fitting, we obtained λ Al to be 688 nm at 4.2 K and 544 nm at 80 K, which are comparable to the values obtained from the spin-valve measurements ( Fig.…”

“…The electrical resistivities of the Al and Py wires were measured to be 7.6 × 10 −8 Ω.m (1.15 × 10 −7 Ω.m) and 3.35 × 10 −7 Ω.m (4.76 × 10 −7 Ω.m) at 4.2 K (300 K), respectively. The contact resistances of the Py/Al junctions were accurately measured by the 4-probe method where the current was sourced between one end of the Al channel and one end of the ferromagnet wire, while the voltage was measured between the other end of the Al channel and the other end of the same ferromagnet wire, and found to be less than 10 −15 Ω.m 2 , thus confirming their transparent nature [13].…”

“…The Hanle data was fitted with an analytical expression taking into consideration the transparent nature of the contacts [13,21] and the out-of-plane rotation of the Py magnetization [3]:…”

“…The device preparation is described in detail in the supplementary material [15] and follows Refs. [6,13,14]. Fig.…”

“…But curiously, corresponding spin precession studies in such systems are scarce. Only recently a few groups have demonstrated spin precession in NLSVs with transparent FM/NM interfaces [12,13], with the NM channel being either silver or copper. More importantly, these few experiments have been done only at low temperatures (T ≤ 10 K), with no reports on Hanle measurements at room temperature for transparent FM/NM interfaces.We demonstrate, through non-local spin precession experiments on Py/Al NLSVs with transparent interfaces, an anomalous Hanle lineshape for T > 150 K, in which the in-plane and out-of-plane spin signals are unequal.…”