Spin Resonance in Neutron-Irradiated Graphite

Abstract

The carrier spin-resonance line of neutron-irradiated single crystals of graphite at 300°K has been observed as a function of the thermal neutron flux up to a dose of 9.6×${10}^{18}$ nvt. From the intensity increase and the $g$ shift for $H$ parallel to the $c$ axis, it is concluded that on the average 30 holes become mobile per nvt per ${\mathrm{cm}}^3$. This is in agreement with earlier work of Hennig and Hove which was based on electrical measurements. It is shown that the line they reported in spin-resonance experiments on polycrystalline graphite was due to mobile charge carriers and not to paramagnetic carbon centers as they assumed. The number of holes created is compared to a recent electron transmission microscopy investigation of Bollmann where the damage has been observed directly. It is estimated that about one hole per displaced carbon atom is freed.