Anomalous magnetic properties of Mn-implanted InN thin films

Anomalous magnetic properties of C-axis-oriented Mn-implanted InN thin films on GaN/sapphire substrates are reported. X-ray diffraction analysis revealed Mn-implanted InN films of a high-quality crystal phase with wurtzite structure. All samples show n-type conductivity by Hall measurements. The un-implanted InN/GaN/Al2O3 sample with a carrier concentration of 1.6 × 1021 cm− 3 (n2D = 8 × 1016 cm− 2) exhibits increasing magnetization with decreasing temperature and did not appear superconductive above 1.8 K. After Mn-ion implantation, the appearance of the Meissner effect with superconducting onset temperature near 2.4 K was observed. The superconducting volume fraction χ is near 36% at 2.2 K. Moreover, type-II behavior was further characterized by field-dependent magnetization measurement.