電子ビーム蒸着法により作製したMgB₂薄膜のピンニングセンター

抄録

We prepared MgB₂ thin films on polished sapphire C-plane single-crystal substrates using an electron beam evaporation technique and various deposition conditions in order to investigate the flux pinning centers in MgB₂. We confirmed that the grain boundaries of MgB₂ crystals act as effective pinning centers by comparing the magnetic properties of the thin films prepared at different substrate temperatures while maintaining the stoichiometric composition. We also found that the Mg deficiencies or the B substitutions on Mg sites in MgB₂ crystals could be effective pinning centers by comparing the magnetic properties of the thin films prepared at the same substrate temperatures while changing the chemical composition. Evaluating the MgB₂ films deposited with O₂ gas in the chamber, we found that MgO in the MgB₂ films may also act as effective pinning centers.