Effects of Hole Doping by Neutron Irradiation on Magnetic-Field Induced Electronic Phase Transitions in Graphite

We have investigated effects of hole doping by fast-neutron irradiation on the magnetic-field induced phase transitions in graphite using specimens irradiated with fast neutrons. Resistance measurements have been done in magnetic fields of up to above 50 T and at temperatures down to about 1.5 K. The neutron irradiation creates latticed effects acting as acceptors, affecting the imbalance of the electron and hole densities and the Fermi level. We have found that there entrant transition field shifts towards lower fields with hole doping, suggestive of the participation of the electron subband in the magnetic-field induced state.