Magnetic properties of ion-implanted diamond

Single crystalline diamond samples of type IIa were implanted with boron and CVD diamond samples with fluorine or iron ions. Defect rich surface layers extending to a depth of about 300 nm for boron and 1 mu m for fluorine and iron were produced by multiple energy implantation. The ion concentrations at the implanted regions were between 30 and 600 ppm for iron and fluorine and 0.5 to 1.5 at.% for boron. In all samples the magnetic properties were dominated by the diamagnetism of pure diamond. The main influence of iron and fluorine implantation on the magnetic properties of diamond is the creation of paramagnetic centres induced by disorder. Whereas diamond implanted with boron at a temperature of 900 degrees C does not show detectable paramagnetism. After subtraction of the linear background all implanted samples show small ferromagnetic-like loops. Although these signals are clearly above the detection limit and appear to be caused by ferromagnetism, we show that the measured loops are mainly caused by a SQUID artefact. We did not find any evidence for the existence of superconductivity in boron-doped diamond samples prepared under the used conditions. (c) 2007 Elsevier B.V. All rights reserved.