Spin pump and probe in lanthanum strontium manganite/platinum bilayers

G Y Luo,J G Lin,Ching-Ray Chang,Wen-Chung Chiang

doi:10.1038/s41598-017-06861-1

G Y Luo, J G Lin + Show 2 more

Open Access

https://doi.org/10.1038/s41598-017-06861-1

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Abstract

Ferromagnetic resonance driven spin pumping (FMR-SP) is a novel method to transfer spin current from the ferromagnetic (FM) layer into the adjacent normal metal (NM) layer in an FM/NM bilayer system. Consequently, the spin current could be probed in NM layer via inverse spin Hall effect (ISHE). In spite of numerous ISHE studies on FM/Pt bilayers, La0.7Sr0.3MnO3(LSMO)/Pt system has been less explored and its relevant information about interface property (characterized by spin mixing conductance) and spin-charge conversion efficiency (characterized by spin Hall angle) is a matter of importance for the possible applications of spintronic devices. In this work, the technique of FMR-SP has been applied on two series of LSMO/Pt bilayers with the thickness of each layer being varied. The thickness dependences of ISHE voltage allow to extract the values of spin mixing conductance and spin Hall angle of LSMO/Pt bilayers, which are (1.8 ± 0.4) × 1019 m−2 and (1.2 ± 0.1) % respectively. In comparison with other FM/Pt systems, LSMO/Pt has comparable spin current density and spin mixing conductance, regardless its distinct electronic structure from other ferromagnetic metals.

Highlights

Nowadays the conventional, charge-based electronics has reached a bottleneck for further development of miniaturizing the devices due to the fatal issues such as thermal fluctuation-induced noises and energy loss by Joule heating
In either spin Hall effect (SHE) or inverse spin Hall effect (ISHE), the efficiency of spin-charge conversion is characterized by spin Hall angle which is strongly related to the intrinsic electronic structures of materials
The topological information indicates that the LSMO film is rather smooth with a root-mean-square roughness around 0.4 nm within the scanning area of 5 × 5 μm[2]

Summary

Introduction

Charge-based electronics has reached a bottleneck for further development of miniaturizing the devices due to the fatal issues such as thermal fluctuation-induced noises and energy loss by Joule heating. In either SHE or ISHE, the efficiency of spin-charge conversion is characterized by spin Hall angle (θISHE, defined as the ratio of charge current vs spin current) which is strongly related to the intrinsic electronic structures of materials. ISHE has been investigated by means of either nonlocal magneto-transport measurement[12] or spin pumping ferromagnetic resonance (SP-FMR)[10, 13,14,15,16,17]. For the value of θISHE of Platinum (Pt), the techniques of spin-torque-induced ferromagnetic resonance[18] and modulation of damping[19, 20] estimate it from 7.6 to 11%; whereas it varies from 0.67 to 8%13–17, 21–23 derived from FMR-SP technique with either coplanar waveguide or cavity mode. The values of spin mixing conductance in the second last column were mostly obtained with spin pumping technique (refs 48)

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Conclusion