Spin-to-Charge Conversion in All-Oxide La_2/3Sr_1/3MnO₃/SrIrO₃ Heterostructures

Spin injection and spin-charge conversion processesin all-oxideLa(2/3)Sr(1/3)MnO(3)/SrIrO3 (LSMO/SIO)heterostructures with different SIO layer thickness and interfacialfeatures have been studied. Ferromagnetic resonance (FMR) techniquehas been used to generate pure spin currents by spin pumping (SP)in ferromagnetic (FM) half-metallic LSMO. The change of the resonancelinewidth in bare LSMO layers and LSMO/SIO heterostructures suggestsa successful spin injection into the SIO layers. However, low valuesof the spin mixing conductance, compared to more traditional permalloy(Py)/Pt or yttrium iron garnet (YIG)/Pt systems, are found. A thoroughanalysis of the interfaces by high-resolution scanning transmissionelectron microscopy (HR-STEM) imaging suggests that they are structurallyclean and atomic sharp, but a compositional analysis by energy-dispersiveX-ray spectroscopy (EDS) reveals the interdiffusion of La, Ir, andMn atomic species in the first atomic layers close to the interface.Inverse spin Hall effect (ISHE) measurements evidence that interfacialfeatures play a very relevant role in controlling the effectivenessof the spin injection process and low transversal ISHE voltage signalsare detected. In addition, it is found that larger voltage signalsare detected for the lowest SIO layer thickness highlighting the roleof the spin diffusion length (& lambda;(sd))/SIO layer thicknessratio. The values of ISHE voltage are rather low but allow us to determinethe spin Hall angle of SIO (& theta;(SH) & AP; 1.12% at T = 250 K), which is remarkably similar to that obtainedfor the well-known Py/Pt system, therefore suggesting that SIO couldbe a promising spin-Hall material.