Nanometre-thick Si/Al Gradient Materials for Sustainable Spin Current Generation

Abstract Green materials for electron spin manipulation are essential for common spintronic applications. Recent studies have documented the efficient generation of spin torque using spin-orbit interactions (SOIs); however, SOI use relies on the employment of rare metals such as platinum. Here, we demonstrate that a nanometre-thick gradient from silicon to aluminium, which consists of readily available elements from earth resources, can produce a spin torque over three times as large as that of platinum, despite the weak SOI of these compositions. The spin-torque efficiency can be improved by decreasing the thickness of the gradient, while a sharp interface was not found to increase the spin torque. Moreover, the electric conductivity of the gradient material can be up to twice as large as that of platinum, which provides a way to reduce Joule heating losses and signal delays in spintronic device circuits. Our findings represent a pathway for sustainable spin manipulation.