Enhancement of superconducting parameters of MgB2 by low energy carbon ion implantation

Highlights: • More grain connectivity observed after irradiation. • MgB₂ samples become more magnetic resistive after ion irradiation. • Critical current density (J_c) has improved fourfold after irradiation from 1 × 10⁴ A/cm² to 4 × 10⁴ A/cm² measured at 5 K. • Peak corresponding to E_2g mode in Raman Spectra found to follow red shift with increase in fluence. -- Abstract: The aim of work is to study the effects of carbon ion implantation on enhancement of superconducting properties of MgB₂. Pure MgB₂ bulk samples are irradiated by carbon ion beam of energy 40 keV (beam current 1 µA) at different fluences. After irradiation, there is enhancement in superconducting properties viz., critical current density (J_c), critical magnetic field (H_c2), comparing to pristine sample. Estimated with Ginzburg-Landau theory method at zero kelvin, the critical magnetic field H_c2(0) for irradiated sample shows an increase of 47 T than that of 38 T reported for pristine sample. There is also a four times increase in J_c after implantation. Improvement in grain connectivity with ion fluence is found in surface morphological studies. Raman spectroscopic studies show a shift in resonance peak related with E_2g phonon modes after irradiation. This shifting is caused due to improvement in scattering and alteration of Fermi surface in implanted samples. These results are explained in correlation with the lattice disorder.