Enhancement of the critical current density in FeO-coated MgB₂ thin films at high magnetic fields

The effect of depositing FeO nanoparticles with a diameter of 10 nm onto the surface of MgB₂ thin films on the critical current density was studied in comparison with the case of uncoated MgB₂ thin films. We calculated the superconducting critical current densities (J_c) from the magnetization hysteresis (M–H) curves for both sets of samples and found that the J_c value of FeO-coated films is higher at all fields and temperatures than the J_c value for uncoated films, and that it decreases to ~10⁵ A/cm² at B = 1 T and T = 20 K and remains approximately constant at higher fields up to 7 T.