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Joel S. Helton, Assistant Professor

Colossal Magnetoresistance

Materials displaying magnetoresistance, where the electrical conductivity changes due to an applied magnetic field, are currently used in the magnetic field sensors that enable modern magnetic data storage.  Some materials, such as La0.7Ca0.3MnO3, display colossal magnetoresistance.  This effect is important both due to the possibility improved technological devices and also because of the rich physics underlying this effect, which comes from the strong coupling between the magnetic, electric, lattice, and orbital degrees of freedom in these materials as well as phase competition over a variety of length scales.

I am interested in performing inelastic neutron scattering experiments on single-crystal sample of colossal magnetoresistive manganties to better understand the short-range magnetic correlations and structural excitations that are present near the combined ferromagnetic and metal-insulator phase transition that is central to the effect.  Midshipmen interested in this project can participate immediately in analyzing data from previous scattering experiments.  Students will also have the opportunity to collect inelastic neutron scattering data in experiments at the NIST Center for Neutron Research.


The neutron scattering dynamic structure factor for La0.7Ca0.3MnO3, measured using the ARCS spectrometer at Oak Ridge National Lab.

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