Pinning effects and current density broadening of resistance on MgB 2

We prepared the indium doped MgB ₂ bulk sample by conventional solid state reaction. Systematic measurements of resistance versus temperature were performed on the sample with different transport current and different applied magnetic field. The curves of resistance in opposition to temperature are broadened with different transport current in transmitting temperature range. We present a method for the first time to analyze the experimental data and explore the pinning mechanisms of MgB ₂ for such kind of experiments. By analyzing on the experimental data, we found that the effective potential U_eff( T, H, J) is of logarithmic form in our experimental temperature and applied magnetic field regime. The curve U₀( T, J) is linear dependent on temperature but the slope coefficient is changing lower near onset critical temperature.