Effect of spin relaxation rate on the interfacial spin depolarization in ferromagnet/oxide/semiconductor contacts

TL;DR

This study investigates how the spin relaxation rate in different semiconductors affects interfacial spin depolarization in ferromagnet/oxide/semiconductor contacts, revealing temperature-dependent variations linked to host material properties.

Contribution

It introduces a model that explains the temperature and bias dependence of interfacial spin depolarization considering spin relaxation and local magnetic fields in the semiconductor.

Findings

Large ISD in CoFe/MgO/Si at room temperature

Small ISD in CoFe/MgO/Ge at room temperature

Increased ISD in CoFe/MgO/Ge at low temperature

Abstract

Combined measurements of normal and inverted Hanle effects in CoFe/MgO/semiconductor (SC) contacts reveal the effect of spin relaxation rate on the interfacial spin depolarization (ISD) from local magnetic fields. Despite the similar ferromagnetic electrode and interfacial roughness in both CoFe/MgO/Si and CoFe/MgO/Ge contacts, we have observed clearly different features of the ISD depending on the host SC. The precession and relaxation of spins in different SCs exposed to the local fields from more or less the same ferromagnets give rise to a notably different ratio of the inverted Hanle signal to the normal one. At room temperature, a large ISD is observed in the CoFe/MgO/Si contact, but a small ISD in the CoFe/MgO/Ge contact. The ISD of the CoFe/MgO/Ge contact has been substantially increased at low temperature. These results can be ascribed to the difference of spin relaxation in host SCs. A model calculation of the ISD, considering the spin precession due to the local field and the spin relaxation in the host SC, explains the temperature and bias dependence of the ISD consistently.