Exchange-driven spin relaxation in ferromagnet/oxide/semiconductor heterostructures

TL;DR

This study reveals how exchange-driven hyperfine fields influence electron spin relaxation in GaAs near ferromagnetic layers, showing temperature-dependent effects linked to carrier localization, and clarifies the origin of low-temperature spin relaxation.

Contribution

It provides new insights into the role of exchange-driven hyperfine interactions in spin relaxation, especially at low temperatures, advancing understanding of spin dynamics in ferromagnet/oxide/semiconductor heterostructures.

Findings

Spin relaxation time depends strongly on exchange-driven hyperfine field strength.

Low-temperature spin lifetime is dominated by hyperfine field inhomogeneity due to carrier localization.

Results clarify the origin of spin relaxation in GaAs under magnetic fields at low temperatures.

Abstract

We investigate electron spin relaxation in GaAs in the proximity of a Fe/MgO layer using spin-resolved optical pump-probe spectroscopy, revealing a strong dependence of the spin relaxation time on the strength of an exchange-driven hyperfine field. The temperature dependence of this effect reveals a strong correlation with carrier freeze out, implying that at low temperatures the free carrier spin lifetime is dominated by inhomogeneity in the local hyperfine field due to carrier localization. This result resolves a long-standing and contentious question of the origin of the spin relaxation in GaAs at low temperature when a magnetic field is present. Further, this improved fundamental understanding paves the way for future experiments exploring the time-dependent exchange interaction at the ferromagnet/semiconductor interface and its impact on spin dissipation and transport in the regime of dynamically-driven spin pumping.