Flux Pinning Centers in ${\rm MgB}_{2}$ Thin Films Prepared by an Electron Beam Evaporation Technique

Abstract

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.