磁性グラニュラー薄膜を用いた人工微小構造におけるスピン依存単電子トンネル現象

概要

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Spin-dependent single clectron tunneling was investigated in microfabricated granular systems. Two types of sample structures were fabricated : granular nanobridges and CPP geometry structures. The granular nanobridge consists of electrodes separated by a nanometer-sized gap filled with a thin insulating Co_<36>Al_<22>O_<42> granular film. Coulomb blockade with a clear threshold voltage (V_<th>) is observed at 4.2 K, and the tunnel magnetoresistance (TMR) is cnhanced at a voltage slightly above V_<th>. This enhancement is explained by the orthodox theory of single-electron tunneling in ferromagnetic multiple junctions. The CPP geometry structure consists of a thin Co_<36>Al_<22>O_<42> granular film sandwiched by top and bottom electrodes with a submicron-sized contact area. Clear Coulomb staircases are observed as a result of the addition of an Al-O bottleneck layer. which leads to an asymmetric configuration of tunnel resistances. Furthermore, the TMR shows oscillatory behavior associated with the Coulomb staircase.
社団法人日本磁気学会の論文
2003-03-01