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

摘要

Combined measurements of normal and inverted Hanle effects inCoFe/MgO/semiconductor (SC) contacts reveal the effect of spin relaxation rateon the interfacial spin depolarization (ISD) from local magnetic fields.Despite the similar ferromagnetic electrode and interfacial roughness in bothCoFe/MgO/Si and CoFe/MgO/Ge contacts, we have observed clearly differentfeatures of the ISD depending on the host SC. The precession and relaxation ofspins in different SCs exposed to the local fields from more or less the sameferromagnets give rise to a notably different ratio of the inverted Hanlesignal to the normal one. At room temperature, a large ISD is observed in theCoFe/MgO/Si contact, but a small ISD in the CoFe/MgO/Ge contact. The ISD of theCoFe/MgO/Ge contact has been substantially increased at low temperature. Theseresults can be ascribed to the difference of spin relaxation in host SCs. Amodel calculation of the ISD, considering the spin precession due to the localfield and the spin relaxation in the host SC, explains the temperature and biasdependence of the ISD consistently.