Thom Mason

Condensed Matter Physics (Experimental)

B.Sc., Dalhousie (1986), Ph.D., McMaster (1990), NSERC Postdoctoral Fellow, AT&T Bell Laboratories, Murray Hill (1990-1991), Senior Scientist, Risų National Laboratory, Denmark (1992-1993), Assistant & Associate Professor, University of Toronto (1993-1998), Associate of the Canadian Institute for Advanced Research - Superconductivity Program (1993-present), Alfred P. Sloan Research Fellow (1997-1999), Director: Experimental Facilities Division, Spallation Neutron Source, (1998-2001), Associate Laboratory Director for the Spallation Neutron Source, Oak Ridge National Laboratory, (2001-present).

Experimental condensed matter; magnetism; neutron scattering; highly correlated electron systems - high temperature and heavy fermion superconductors; frustrated magnetic systems.

Telephone: (865) 241-1499

Fax: (865) 576-3041

E-mail: masont at sns.gov

Research Interests

Because the neutron has a magnetic moment it is able to probe the magnetic moments found in many solids. The energy and wavelength of neutrons in the moderator of a nuclear reactor are well matched to the energy and length scales relevant in condensed matter, giving us a probe of unique power. The capabilities range from the determination of the nature of magnetic ordering below a phase transition to directly probing the magnetic fluctuations of electrons in metals.

This last technique has recently been very successful in providing details of the behaviour of systems in which correlations between electrons are of particular importance, such as high temperature superconductors and heavy fermion systems. Both systems are particularly interesting because they have in common a failure of conventional descriptions based on the assumption that the electrons can be viewed as effectively non-interacting. To the left is a multicrystal mount of seven aligned single crystals used to study the high energy magnetic excitations in La2CuO4.

The figure below shows a map of the inelastic magnetic neutron scattering from a high temperature superconductor at 297 K as a function of momentum transfer. This gives us a detailed picture of the spacial distribution of magnetic fluctuations which are responsible for the anomalous properties of these materials.

The neutron scattering research is carried out at large facilities in North America and Europe. The European facilities used are Risų National Lab near Copenhagen and ISIS (the world's highest flux spallation neutron source) near Oxford. The highest flux neutron source in the U.S. is the HFIR reactor at Oak Ridge which is currently being upgraded by the addition of a cold neutron source and new instrumentation. For information about other neutron scattering sources try the Neutron Scattering Home Page .

Some recent preprints are available from the Los Alamos Preprint Archive.

Lectures on Neutron Sources, Neutron Detectors, and Neutron Instrumentation for the Neutron and X-ray Scattering Summer School:
(these are large powerpoint files):

A recent talk on neutron scattering studies of spin fluctuations in high temperature superconductors:

Return to Spallation Neutron Source or Oak Ridge National Laboratory homepage.

This page is maintained by Thom Mason.

Last modified March 24, 2004.

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