High-frequency spin transport in thin aluminum calculated by spin drift-diffusion equation

Abstract

Lateral spin valves (LSV) are an essential element in spintronics research and applications. The separation of spin injection and spin detection in the LSV makes it a useful platform for studying fundamental physics (e.g., spin relaxation) and building nanoscale devices (spin transistors, magnetic sensors, etc.). To drive many LSV-based prototypes closer to production, there is a need to evaluate the LSV performance under high-frequency (e.g., gigahertz) operations, especially with information spectra rather than single tones. Here we calculate gigahertz spin transport in a nonmagnetic channel of the LSV using a pseudo-random binary sequence as an input signal to mimic information. We solved the time-dependent spin drift-diffusion equation and provide an integral solution for the transmitted spin polarization. A frequency-dependent spin transport length is found that shows high-frequency spin signals transmit much less efficiently than low-frequency spin signals. An applied electric field consistent with the high resistance of thin films is shown to improve transmission. The transmitted signal strength and its signal-to-noise ratio (SNR) are analyzed with respect to the transmission distance, the diffusion coefficient, and an applied electric field along the channel; these effects can be explained in the frequency domain. Finally, we calculated gigahertz spin transport in a thin aluminum channel and obtained an SNR >20 dB, which is a value that exceeds the SNR of the input signal. This demonstrates the great potential of LSV-based miniaturized spintronic devices to transmit information in high-frequency regimes.