Noise Measurements of Low-impedance NiFe/Al2O3/NiFe Tunnel Junctions.

  • Kinoshita H.
    Graduate School of Science, Tokyo Metropolitan Univ.
  • Mizuno T.
    Graduate School of Science, Tokyo Metropolitan Univ.
  • Aoki Y.
    Graduate School of Science, Tokyo Metropolitan Univ.
  • Sugawara H.
    Graduate School of Science, Tokyo Metropolitan Univ.
  • Sato H.
    Graduate School of Science, Tokyo Metropolitan Univ.
  • Matsuda K.
    Functional Materials Research Lab., NEC Corporation
  • Mitsuzuka T.
    Functional Materials Research Lab., NEC Corporation
  • Kamijo A.
    Functional Materials Research Lab., NEC Corporation
  • Tsuge H.
    Functional Materials Research Lab., NEC Corporation

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Other Title
  • 低インピーダンス強磁性トンネル接合NiFe/Al2O3/NiFeのノイズ測定
  • テイインピーダンス キョウジセイ トンネル セツゴウ NiFe Al2O3 NiFe ノ ノイズ ソクテイ

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This paper reports noise measurements of low-impedance NiFe/Al2O3/NiFe tunnel junctions. For samples with a junction area of 4 × 4 μm2, the noise spectrum density shows 1/f-like increase at low frequencies. of the 1/f-like noise depends on bias as V2 and decreases with decreasing temperature as (300 K)/ (77 K)∼4. In an external magnetic field of 60 Oe, where coupling of the two ferromagnetic layers changes from parallel to antiparallel, 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 μm2), (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 1μm2.

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