Flux Pinning Centers in MgB2 Thin Films Prepared by an Electron Beam Evaporation Technique

We prepared MgB₂ thin films by an electron beam evaporation technique and found that either vacancies and/or B substitutions on Mg sites worked as effective pinning centers in MgB₂. We also found that the grain boundaries formed by the columnar grains work as effective pinning centers, by measuring transport J _c´s by changing the relative angle between grain boundaries and the applied magnetic field. We also found that introduced MgO nano-particles in MgB₂ work as effective pinning centers.