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"Beta-NMR: magnetic resonance from thin films and buried interfaces."

Relatore: Andrew MacFarlane- Chemistry Department, Vancouver, Canada

Aula Newton
04 Febbraio 2004 ore 16.30

By virtue of the easy detectability of the high energy decay products of nuclear disintegrations, radioactive nuclei have found many applications in the study of condensed matter, particularly in situations where conventional methods are hampered by the relative scarcity of the atoms of interest, for example dilute impurities in semiconductors. Recently we have developed a pair of beta-detected-NMR spectrometers employing the intense low energy spin-polarized beams of radioactive ions available at the new ISAC facility at TRIUMF. In this method, the nuclear magnetic resonance or relaxation is detected through the anisotropic beta decay of the probe nucleus, yielding the detailed local magnetic information familiar from conventional NMR experiments, but using approximately 10 orders of magnitude fewer nuclei. By electrostatic deceleration of the ion beam from its nominal energy of 30 keV, we can vary the average implantation depth of the ions from a few hundred nanometres down to a few nm. We plan to use this capability to study ultrathin films and nanostructured materials, where there are many interesting questions regarding, for example, the electronic and magnetic properties of buried interfaces and nanoscale electronic confinement effects. I will summarize our progress in this direction, and present an outlook for the future of the technique.