低インピーダンス強磁性トンネル接合NiFe/Al_2O_3/NiFeのノイズ測定

概要

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This paper reports noise measurements of low impedance NiFe/Al_2O_3/NiFe tunnel junctions. For samples with a junction area of 4×4 μm^2, the noise spectrum density Sv shows 1/f-like increase at low frequencies. Sv of the 1/f-like noise depends on bias as V^2 and decreases with decreasing temperature as Sv (300 K)/Sv (77 K)〜4. In an external magnetic field of 60 Oe, where coupling of the two ferromagnetic layers changes from parallel to antiparallel, Sv at 77 K is strongly enhanced and its frequency dependence has a shoulder-like anomaly. For a sample with a smaller junction area (2×2 μm^2), Sv(f) also shows a shoulder-like anomaly even at room temperature in a zero field. In the time domain, two-level fluctuation (telegraph noise) was observed. This observation indicates the existence of fluctuators with spatial scale of the order of 1 μm^2.
社団法人日本磁気学会の論文
2001-04-15