Zaven Altounian Ph.D. (McMaster '76) Faculty Professor 398-6535, [email protected]

My research interests are centered on metallic glasses, thin films, and magnetic materials.

Metallic glasses have physical properties distinctly different from those of the corresponding crystalline alloys, arising from the structure of the glassy state. Although glasses have no long range order they do possess short range order. The nature of the short range order depends on the composition as well as the relaxation state of the glass. We study the structure and relaxation using a combination of X-ray and neutron scattering techniques. Some of the physical properties that we study are electrical resistivity, spin-fluctuations, and superconductivity.

We manufacture thin films and magnetic multilayers using a multitarget DC and RF magnetron sputtering system. In particular we study films which consist of alternating layers of magnetic and non-magnetic metals which exhibit giant magnetoresistance and for small saturation fields, the films can be used as magnetoresistance sensors. Identifying simple multilayer systems with appropriate characteristics still remains a problem in this field. Apart from transport property measurements we use polarized neutron reflectometry and X-ray scattering techniques, both wide and small angle, to study the magnetic as well as the crystal structure of the multilayers and to characterize the interlayer roughness as well as the overall roughness.

Giant magnetocaloric materials (GMC) undergo a large change in magnetic entropy upon the application of a magnetic field. GMC materials that exhibit this effect near room temperature, are prime candidates for use as refrigerants in magnetic refrigeration. GMC is observed when a structural transition is coupled to a magnetic transition. We have studied R₅M₄ compounds, where R is a rare-earth element and M is Si, Ge, or Sn. At present we are interested in other compounds that exhibit the GMC effect, such as Laves phases and LaFe₁₃ based compounds.