Abstract
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.
