微小強磁性体におけるスピン依存トンネリングとクーロン・ブロッケイド

概要

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We theoretically study spin-dependent tunneling in a ferromagnetic single-electron transistor (SET) containing ferromagnetic electrodes and a small ferromagnetic island. In the SET, the tunnel resistance depends on the relative orientation of magnetizations between the electrodes and island. In addition, a tunneling electron on the island causes an increase in electrostatic energy due to the charging effect. At high temperatures, sequential single-electron tunneling dominates the tunneling processes in the SET, while at low temperatures it is superseded by cotunneling of electrons through both junctions. Since cotunneling is a higher-order tunneling process, the resistance of the SET in the cotunneling regime becomes sensitive to the relative orientation of magnetizations. Consequently, the tunnel magnetoresistance (TMR) is enhanced in the Coulomb blockade regime. We discuss the TMR of the SET as a function of temperature, bias, and gate voltages in connection with recent experiments in ferromagnetic double junctions and granular films.
社団法人日本磁気学会の論文
1999-04-01