Suppression of spin rectification effects in spin pumping experiments

Sergi Martin-Rio,Lluis Balcells,Carlos Frontera,Alberto Pomar,Benjamin Martinez

doi:10.1038/s41598-021-04319-z

Sergi Martin-Rio, Lluis Balcells + Show 3 more

Open Access

https://doi.org/10.1038/s41598-021-04319-z

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Abstract

Spin pumping (SP) is a well-established method to generate pure spin currents allowing efficient spin injection into metals and semiconductors avoiding the problem of impedance mismatch. However, to disentangle pure spin currents from parasitic effects due to spin rectification effects (SRE) is a difficult task that is seriously hampering further developments. Here we propose a simple method that allows suppressing SRE contribution to inverse spin Hall effect (ISHE) voltage signal avoiding long and tedious angle-dependent measurements. We show an experimental study in the well-known Py/Pt system by using a coplanar waveguide (CPW). Results obtained demonstrate that the sign and size of the measured transverse voltage signal depends on the width of the sample along the CPW active line. A progressive reduction of this width evidences that SRE contribution to the measured transverse voltage signal becomes negligibly small for sample width below 200 μm. A numerical solution of the Maxwell equations in the CPW-sample setup, by using the Landau-Lifshitz equation with the Gilbert damping term (LLG) as the constitutive equation of the media, and with the proper set of boundary conditions, confirms the obtained experimental results.

Highlights

Spin pumping (SP) is a well-established method to generate pure spin currents allowing efficient spin injection into metals and semiconductors avoiding the problem of impedance mismatch
At the resonance frequency an absorption Lorentzian-shaped peak appears in the transmission coefficient of the coplanar waveguide (CPW), S, whose derivative is described by the expression[26]: dS d =
spin rectification effects (SRE) are generated by a microwave eddy current circulating through the sample due to the inductive coupling between the sample and the signal line of the CPW

Summary

Introduction

Spin pumping (SP) is a well-established method to generate pure spin currents allowing efficient spin injection into metals and semiconductors avoiding the problem of impedance mismatch. This method requires a large number of samples and measurements, as well as a proper account of the thickness dependence of different parameters, such as the resistivity of the FM or the spin mixing conductance Separation of both signals by using the different behavior of ISHE and SRE under the inversion of the direction of spin injection has been r eported[24,25]. In this work we propose a new method to suppress the SRE contribution leading to a straightforward measurement of the ISHE transverse voltage signal in SP experiments in FM/NM bilayers This method can be implemented and allows a full suppression of the SRE signal in SP experiments in coplanar waveguide (CPW) and microstrip experimental setups

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