Temperature Dependence of the Flux Jump Upper Threshold Field in MgB_2 Thin Films(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

概要

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The origin of the magnetic flux noise in MgB_2 thin films is believed to be a thermo-magnetic instability, where the local dissipation created by vortex motion leads to reduced pinning, and forms a positive feedback loop which can develop into a thermo-magnetic runaway. However, only the lower threshold field (H_1) for the appearance of this noise was investigated by the magneto-optics (MO) technique due to the field limit of the MO indicator. In this paper, we report the upper threshold field, (H_u) which is successfully obtained by different technique using a vibrating sample magnetometer while varying temperature and the field interval. After the analysis of magnetic hysteresis curves, we found that H_u is strongly depends on sample geometry and temperature. This is consistent with the phenomenological model mentioned above.
社団法人日本物理学会の論文
2008-10-15