Properties of MgB2 Thin Films Deposited on Different Substrates Prepared by Ex-Situ Annealing Process

Abstract

MgB2 thin films were deposited on MgO (100) substrate and r-plane Al2O3 (1102) substrate by ex-situ annealing of boron film in magnesium vapor. The thickness of ex-situ annealed MgB2 films is approximately 600 nm according to data observation by ellipsometer. The magnetic properties of samples were determined using a vibrating sample magnetometer. The magnetic field dependence of the critical current density J c was calculated from M–H loops and also the magnetic field dependence of F p was compared for the different temperature ranges from 5 to 25 K. The critical current density J c was found to be around 1.0×106 A/cm2 and 1.7×106 A/cm2 in zero field at 5 K for MgB2 films deposited on MgO and r-plane Al2O3 substrates, respectively. It was found that the critical current density of the film deposited on MgO became stronger than that of r-plane Al2O3 in the magnetic field. The superconducting transition temperature was determined by ac susceptibility measurement using physical properties measurement system. acsusceptibility measurements for MgB2 films deposited on MgO and r-plane Al2O3 substrates were performed as a function of temperatures at constant frequency and ac field amplitude in the absence of dc bias field. The critical current densities as a function of temperature were estimated from the ac susceptibility data.