Dynamic detection of electron spin accumulation in ferromagnet-semiconductor devices by ferromagnetic resonance

TL;DR

This paper introduces a novel ferromagnetic resonance-based method for detecting electron spin accumulation in ferromagnet-semiconductor devices, effective at room temperature and capable of measuring very short spin lifetimes.

Contribution

The study presents a new electrical detection technique using ferromagnetic resonance to observe spin accumulation, overcoming limitations of traditional Hanle effect methods.

Findings

Effective detection of spin accumulation from 30 to 300 K.

Ability to measure spin lifetimes shorter than 100 picoseconds.

Verification of the method through comparison with traditional techniques.

Abstract

A distinguishing feature of spin accumulation in ferromagnet-semiconductor devices is precession of the non-equilibrium spin population of the semiconductor in a magnetic field. This is the basis for detection techniques such as the Hanle effect, but these approaches become less effective as the spin lifetime in the semiconductor decreases. For this reason, no electrical Hanle measurement has been demonstrated in GaAs at room temperature. We show here that by forcing the magnetization in the ferromagnet (the spin injector and detector) to precess at the ferromagnetic resonance frequency, an electrically generated spin accumulation can be detected from 30 to 300 K. At low temperatures, the distinct Larmor precession of the spin accumulation in the semiconductor can be detected by ferromagnetic resonance in an oblique field. We verify the effectiveness of this new spin detection technique by comparing the injection bias and temperature dependence of the measured spin signal to the results obtained using traditional methods. We further show that this new approach enables a measurement of short spin lifetimes (< 100 psec), a regime that is not accessible in semiconductors using traditional Hanle techniques.