Magnetic Nanostructures Group
What We Do
Our group uses neutron and x-ray scattering to study nanostructured magnetic materials, such as thin films, multilayers, and patterned structures. At present, we primarily use the NG-1 Reflectometer at the NCNR to conduct polarized neutron reflectometry (PNR) measurements. Specular PNR is sensitive to buried interfaces, and can be used to determine depth profiles of both the magnetitzation and the chemical composition of thin films. Therefore, this technique is uniquely useful for investigating properties important to contemporary magnetic materials research, such as interlayer magnetic coupling, distribution of magnetic moment, magnetic dead layers, impurity diffusion, and interlayer roughness (chemical and magnetic). Off-specular PNR is sensitive to magnetic and structural correlations in the plane of thin film samples, making it a powerful technique for investigating patterned magnetic structures. Additionally, we make use a variety of other neutron spectrometers at the NCNR, as well as instruments at other neutron and synchrotron x-ray facilities.
The NCNR magnetic nanostructures group maintains ongoing collaborations with several institutions including the University of Notre Dame, the Universite Henri Poincare-Nancy, MIT, the Italian Institute for Nanostructured Materials, Los Alamos National Laboratory, and the Stanford Linear Accelerator Center (among others). If you are interested in a collaboration, you can apply for beamtime, or contact one of us directly. Monetary assistance may be available for new facility users. Students are especially encouraged to collaborate. Please check out our "Sample FAQ" for info about what sorts of samples are best for PNR, and examples of what an experiment at our beamline can do for you.
Researchers
Brian Kirby: magnetic semiconductors, exchange coupling, superconductor/ferromagnet heterostructures, NG-1 Reflectometer instrument responsible
Brian Maranville: magnetic thin films, MAGIK neutron spectrometer instrument responsible
Shannon Watson: magnetic tunnel junctions, organic/magnetic hybrid heterostructures
At right: Consider polarized neutron reflectometry used to study ferromagnetic GaMnAs layers separated by a non-magnetic spacer layer. The temperature at which the Q-dependent spin asymmetry (the difference in spin-up and spin-down reflectivities divided by the sum) drastically changes frequency corresponds to a change in the magnetic thickness, showing that the two ferromagnetic layers have different transition temperatures.
