二重強磁性トンネル接合におけるスピン依存伝導特性

概要

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Ferromagnetic double barrier junctions of Co_<75>Fe_<25>/Al_2O_3/Co_<75>Fe_<25>(X)/Al_2O_3/Co_<75>Fe_<25> with discontinuous middle Co_<75>Fe_<25> layers (X=0, 0.7, 1.3, 2.0 nm) were fabricated, and magnetoresistance of these junctions was measured by a dc-4-probe method. At low temperature, the resistance and TMR ratio increased rapidly. This result implies the existence of a charging effect due to the Coulomb-blockade. At temperatures below 50 K, an ac-modulation method was used to measure bias-voltage dependence of the TMR ratio. We observed an increase in TMR ratio for the case of dc transport at low bias voltage. On the other hand, the TMR ratio decreased for the case of ac transport. At high bias voltage and at high temperature, however, we observed no difference between these methods. Such transport properties could be explained by a co-tunneling process.
社団法人日本磁気学会の論文
2001-04-15