Fe charge state adjustment in ZnO upon ion implantation.

The influence of the ion implantation process on the charge state of dilute (57)Fe impurities implanted as radioactive (57)Mn in ZnO is investigated by (57)Fe emission Mössbauer spectroscopy. One sample is additionally implanted with stable (23)Na impurities. Both Fe(2+) and Fe(3+) charge states are observed, and the Fe(3+)/Fe(2+) ratio is found to increase with the fluence of both (57)Mn/(57)Fe and (23)Na ions, demonstrating that the build-up of Fe(3+) is not related to the chemical nature of the implanted ions.

Magnetism at single isolated iron atoms implanted in graphite.

Mössbauer spectra obtained after implantation of 57Fe into highly oriented pyrolytic graphite (HOPG) show a combined magnetic and quadrupole interaction with a magnetic hyperfine field Bhf = 32.6 T at 14 K. Though magnetic effects in nominally diamagnetic HOPG have been reported recently, no experiment has previously shown the existence of magnetism at the atomic scale.