Investigation of critical properties in MgB2/SiC/Si thin films prepared under varied conditions

Critical magnetic properties of MgB2 thin films grown on SiC/Si substrate are investigated with different preparation conditions. MgB2 films were prepared by sequential evaporation of boron and magnesium on SiC buffered Si substrate. The substrate temperature and the amount of supplied boron was varied and influence of varied conditions is investigated. The maximum superconducting transition temperature obtained is 34.5 K. The upper critical field H-c2 is estimated from the onset of AC diamagnetic susceptibility. The temperature dependence is generally linear, being fitted with vertical bar dH(c2)/dT vertical bar around 3 similar to 7 kOe/K depending on the substrate temperature during in situ annealing as well as the magnetic field direction. The critical current density is evaluated from DC magnetization hysteresis to be more than 10(6) A/cm(2) at lower temperatures. Irreversibility field scales with [1 - (T/T-c)(2)](n) with critical exponents n of 3 similar to 7. Correlations among critical properties, crystal qualities and sample preparation conditions are discussed.