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Flux Noise in MgB2 Thin Films

Orjan Festin·Peter Svedlindh·W. N. Kang·Eun-Mi Choi·Sung-Ik Lee
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Abstract

We have performed flux noise and AC-susceptibility measurements on two 400 nm thick MgB$_2$ films. Both measurement techniques give information about the vortex dynamics in the sample, and hence the superconducting transition, and can be linked to each other through the fluctuation-dissipation-theorem. The transition widths for the two films are 0.3 and 0.8 K, respectively, and the transitions show a multi step-like behavior in the AC-susceptibility measurements. The same phenomenon is observed in the flux noise measurements through a change in the frequency dependence of the spectral density at each step in the transition. The results are discussed and interpreted in terms of vortices carrying an arbitrary fraction of a flux quantum as well as in terms of different macroscopic regions in the films having slightly different compositions, and hence, different critical temperatures.

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Orjan Festin, Peter Svedlindh, W. N. Kang, Eun-Mi Choi, Sung-Ik Lee. 2003-03-27. Flux Noise in MgB2 Thin Films. https://doi.org/10.1117/12.490189

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