Spin Seebeck effect and thermal spin galvanic effect in Ni80Fe20/p-Si bilayers

TL;DR

This paper demonstrates efficient thermal generation and detection of spin currents in Ni80Fe20/p-Si bilayers, revealing a giant inverse spin-Hall effect and thermal spin-orbit torques that could advance silicon-based spintronics and memory devices.

Contribution

It reports the first observation of giant inverse spin-Hall effect and thermal spin-orbit torques in Ni80Fe20/p-Si bilayers without heavy metals, highlighting new mechanisms for spin detection and manipulation.

Findings

Giant inverse spin-Hall effect observed in Ni80Fe20/p-Si bilayers.

Thermal spin-orbit torques induce collapse of magnetic hysteresis.

Efficient thermal spin current generation and detection in silicon-based structures.

Abstract

The development of spintronics and spin-caloritronics devices need efficient generation, detection and manipulation of spin current. The thermal spin current from spin-Seebeck effect has been reported to be more energy efficient than the electrical spin injection methods. But, spin detection has been the one of the bottlenecks since metals with large spin-orbit coupling is an essential requirement. In this work, we report an efficient thermal generation and interfacial detection of spin current. We measured a spin-Seebeck effect in Ni80Fe20 (25 nm)/p-Si (50 nm) (polycrystalline) bilayers without heavy metal spin detector. The p-Si, having the centosymmetric crystal structure, has insignificant intrinsic spin-orbit coupling leading to negligible spin-charge conversion. We report a giant inverse spin-Hall effect, essential for detection of spin-Seebeck effect, in the Ni80Fe20/p-Si bilayer structure, which originates from Rashba spin orbit coupling due to structure inversion asymmetry at the interface. In addition, the thermal spin pumping in p-Si leads to spin current from p-Si to Ni80Fe20 layer due to thermal spin galvanic effect and spin-Hall effect causing spin-orbit torques. The thermal spin-orbit torques leads to collapse of magnetic hysteresis of 25 nm thick Ni80Fe20 layer. The thermal spin-orbit torques can be used for efficient magnetic switching for memory applications. These scientific breakthroughs may give impetus to the silicon spintronics and spin-caloritronics devices.