電子ビーム蒸着法によってAIテープ基板上に作製したMgB2薄膜の輸送特性

概要

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Transport properties of MgB2 thin films on Al tape substrates by EBE(Electron Beam Evaporation) were measured to investigate the flux pinning properties. The MgB2 thin films prepared on Al tape substrates showed high critical current density Jc in magnetic field for B//c as large as the MgB2 thin films prepared on Si and AlsO2 substrates by EBE. In high magnetic field, the nonstoichiometric MgB2 thin film which has excess boron showed higher Jc than the stoichiometric MgB2 thin film. In field angular dependence of Jc, both of the MgB2 thin films showed large peaks which were attributed to c-axis correlated pinning centers for B//c. The magnetic field dependence of the reduced macroscopic pinning force density F=Fp/Fpmax of the stoichiometric MgB2 thin film collapses into a scaling curve such as f(b)=Ab1.15(1-b)2.0. Therefore, the grain boundary acts as the dominant pinning center in the stoichiometric MgB2 thin film. However, the nonstoichiometric MgB2 thin film did not fit into the scaling curve. This result shows that the magnesium deficiency or the substitution of boron for magnesium site act as additional pinning centers.
熊本大学の論文
2010-03-00