My research has been in the experimental investigation of solid state materials that
contain nuclear magnetic moments. The main experimental methods are nuclear magnetic
resonance (NMR), recoil-less gamma ray absorption spectroscopy (Mössbauer spectroscopy),
x-ray diffraction, bulk magnetization measurements (hysteresis, Meissner effect), thermal
measurements (heat capacity, calorimetry), and computer simulation/modeling. The
investigated materials include amorphous alloys, high TC superconductors,
rare-earth permanent magnets, membranes containing drug molecules, and Fe-based
nanocrystalline alloys. Research results have been reported at international
conferences and regional seminars, and published in scientific journals and research
monographs.
My research laboratory on the Holy Cross campus has a Mössbauer spectrometer,
in which a gamma ray source, cobalt-57 in a sealed rhodium matrix, is mechanically
modulated by an ultra-linear constant-acceleration driving motor with a typical maximum
velocity of 12 mm/s. A laser in a Michelson interferometer is used to monitor the
velocity profile. Sample temperature may be continuously regulated down to cryogenic
temperatures of about 15 K or raised to high temperatures up to 700 K. Proportional
detection of the transmitted gamma rays is synchronized with the source motion, and the
data are registered in a multi-channel analyzer in a computer. Mössbauer spectra are
recorded and analyzed to provide information on the atomic and electronic structures of the
material. Techniques such as high vacuum, high pressure helium gas, cryogenic
temperature, high voltage, and digital electronics are used, but each component of the
apparatus is made accessible, suitable for engaging undergraduate students. So far,
there have been five students who have worked in the laboratory during two summer periods
and three regular semesters. The Mössbauer spectrometer has also been used for
teaching in the Experimental Solid State Physics course.
