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

摘要

We theoretically study the recently observed tunnel-barrier-enhanced dcvoltage signals generated by magnetization precession in magnetic tunneljunctions. While the spin pumping is suppressed by the high tunnelingimpedance, two complimentary processes are predicted to result in a sizablevoltage generation in ferromagnet (F)|insulator (I)|normal-metal (N) and F|I|Fjunctions, with one ferromagnet being resonantly excited. Magnetic dynamics inF|I|F systems induces a robust charge pumping, translating into voltage in opencircuits. In addition, dynamics in a single ferromagnetic layer developslongitudinal spin accumulation inside the ferromagnet. A tunnel barrier thenacts as a nonintrusive probe that converts the spin accumulation into ameasurable voltage. Neither of the proposed mechanisms suffers from spinrelaxation, which is typically fast on the scale of the exponentially slowtunneling rates. The longitudinal spin-accumulation buildup, however, is verysensitive to the phenomenological ingredients of the spin-relaxation picture.