Relative strength of thermal and electrical spin currents in a ferromagnetic tunnel contact on a semiconductor

Abstract

The relative magnitude of electrical and thermal spin currents is investigated for a ferromagnetic tunnel contact on a semiconductor. A direct quantitative comparison is made by simultaneously generating electrical and thermal spin currents of opposite sign and determining the compensation point at which the sum of both spin currents vanishes. This avoids the need to determine the magnitude of each spin current. Surprisingly, it is found that in a $\mathrm{C}{\mathrm{o}}_{70}\mathrm{F}{\mathrm{e}}_{30}/\mathrm{MgO}/\mathrm{Si}$ tunnel contact, the thermal spin current driven by a temperature difference of less than 1 K across the contact is comparable to the electrical spin current induced by a bias voltage of about 22 mV. This suggests that the thermal generation of spin current is more efficient than hitherto assumed and should be considered in the design and analysis of spintronic devices that use spin current or spin transfer torque.