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Critical-field anisotropy and fluctuation conductivity in granular aluminum films

Critical-field anisotropy and fluctuation conductivity in granular aluminum films We have measured the upper critical field H c 2 ( θ ) for extreme type-II granular aluminum films much thicker than the coherence length and have found them to display a strong temperature-dependent anisotropy ( H ∥ H ⊥ ≫ 1 ). The temperature dependence of the parallel critical field, H ∥ ( T ) , shows an infinite slope near T c , which we interpret as an indication that these films have a layered structure. The perpendicular critical field, H ⊥ ( T ) , has an upward curvature, reminiscent of the behavior observed in ( SN ) x and some layered compounds. As a result, the anisotropy ratio decreases strongly as the temperature is lowered. We interpret this behavior as a transition towards zero dimensionality (decoupled grains). We have also measured the fluctuation conductivity σ s above T c . We find that, for films with high values of normal-state resistivity, σ s follows a power law characteristic of zero dimensionality far above T c , and characteristic of two dimensionality closer to T c , in agreement with the proposed interpretation of the critical-field data. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Physical Review B American Physical Society (APS)

Critical-field anisotropy and fluctuation conductivity in granular aluminum films

Physical Review B , Volume 16 (9) – Nov 1, 1977
7 pages

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Publisher
American Physical Society (APS)
Copyright
Copyright © 1977 The American Physical Society
ISSN
1095-3795
DOI
10.1103/PhysRevB.16.3936
Publisher site
See Article on Publisher Site

Abstract

We have measured the upper critical field H c 2 ( θ ) for extreme type-II granular aluminum films much thicker than the coherence length and have found them to display a strong temperature-dependent anisotropy ( H ∥ H ⊥ ≫ 1 ). The temperature dependence of the parallel critical field, H ∥ ( T ) , shows an infinite slope near T c , which we interpret as an indication that these films have a layered structure. The perpendicular critical field, H ⊥ ( T ) , has an upward curvature, reminiscent of the behavior observed in ( SN ) x and some layered compounds. As a result, the anisotropy ratio decreases strongly as the temperature is lowered. We interpret this behavior as a transition towards zero dimensionality (decoupled grains). We have also measured the fluctuation conductivity σ s above T c . We find that, for films with high values of normal-state resistivity, σ s follows a power law characteristic of zero dimensionality far above T c , and characteristic of two dimensionality closer to T c , in agreement with the proposed interpretation of the critical-field data.

Journal

Physical Review BAmerican Physical Society (APS)

Published: Nov 1, 1977

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