The fabrication and characterization of MgB2 thin films carrying ferromagnetic pinning centers deposited on different substrates

In this study, MgB2 thin films with a thickness of about 600 nm were deposited on the MgO (100) and r-plane Al2O3 ( ) substrates using a ?two-step? synthesis technique. Firstly, deposition of boron was performed by rf magnetron sputtering on substrates and followed by a post deposition annealing at 850 ºC in magnesium vapour. In order to investigate the effect of Fe2O3 nanoparticles on the structural and magnetic properties of films, MgB2 films were coated with different concentrations of Fe2O3 nanoparticles by a spin coating process. The effects of different concentrations of ferromagnetic Fe2O3 nanoparticles on superconducting properties of obtained films were carried out by using structural (XRD, SEM, AFM), electrical (R-T) and magnetization (M-H, M-T and AC Susceptibility) measurements. It was calculated that anisotropic coefficients were about ? = 1.2 and coherence lengths of 5 nm for the uncoated films on both substrates. As a result of coherence length, the appropriate diameters of Fe2O3 nanoparticles were found to be 10 nm, indicating that these nanoparticles served as the pinning centers. Based on the data obtained from this study, it can be said that the coated films indicated the presence of artificial pinning centers created by Fe2O3 nanoparticles. All the results demonstrated that the films deposited on MgO substrates exhibited better superconducting properties than that of films deposited on r-plane Al2O3 substrates.