Tunnel-barrier-enhanced dc voltage signals induced by magnetization dynamics in magnetic tunnel junctions

TL;DR

This paper provides a theoretical analysis of how tunnel barriers enhance dc voltage signals generated by magnetization dynamics in magnetic tunnel junctions, revealing two mechanisms that produce measurable voltages without significant spin relaxation effects.

Contribution

It introduces two novel mechanisms for voltage generation in magnetic tunnel junctions due to magnetization precession, emphasizing the role of tunnel barriers and spin accumulation.

Findings

Voltage signals are enhanced by tunnel barriers.

Two mechanisms: charge pumping and spin accumulation conversion.

Signals are robust against spin relaxation effects.

Abstract

We theoretically study the recently observed tunnel-barrier-enhanced dc voltage signals generated by magnetization precession in magnetic tunnel junctions. While the spin pumping is suppressed by the high tunneling impedance, two complimentary processes are predicted to result in a sizable voltage generation in ferromagnet (F)|insulator (I)|normal-metal (N) and F|I|F junctions, with one ferromagnet being resonantly excited. Magnetic dynamics in F|I|F systems induces a robust charge pumping, translating into voltage in open circuits. In addition, dynamics in a single ferromagnetic layer develops longitudinal spin accumulation inside the ferromagnet. A tunnel barrier then acts as a nonintrusive probe that converts the spin accumulation into a measurable voltage. Neither of the proposed mechanisms suffers from spin relaxation, which is typically fast on the scale of the exponentially slow tunneling rates. The longitudinal spin-accumulation buildup, however, is very sensitive to the phenomenological ingredients of the spin-relaxation picture.