"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."
The synthesis and crystal growth of novel materials will focus on dilute magnetic semiconductors and frustrated magnets with the preparation of these materials as powders, single crystals, and thin films. The powders will yield information on the extent of solid solution formation; diffusion or ion implantation of transition metals into single crystal substrates will allow for compositional mapping of ferromagnetism; flux growth of single crystals will provide a route to synthesize materials for characterization by neutron scattering; and thin film deposition at low temperatures will permit the study of compositions which typically demonstrate phase separation. The two classes of materials to be investigated, dilute magnetic semiconductors and frustrated magnets, are chosen due to the intense interest in spintronic applications and multiferroic behavior, respectively. Semiconductor crystal lattices will be substituted with various first row transition metal magnetic ions including vanadium, chromium, manganese, iron, cobalt and nickel. The transition metal substitution will have concentrations around five atomic percent such that there is negligible direct interaction between magnetic ions (dilute). These dilute magnetic semiconductor materials demonstrate long range magnetic coupling (ferromagnetism) due to interaction with electronic carriers in the semiconductor. Based on theories of carrier-induced ferromagnetism, several variables, including the bandgap energy, carrier density and exchange coupling strength, affect the ferromagnetic Curie temperature. Therefore, ternary phosphide, arsenide, selenide and telluride materials are predicted to be strong candidate host lattices for carrier-mediated ferromagnetism. For the frustrated magnetic materials, the growth of single crystals from high temperature fluxes will be explored for the following compounds: ACr2S4, where A= Zn, Cd or Hg, in order to study the magnetic properties (and possible structural properties in the case of CdCr2S4) which depend on the interplay between the nearest and next nearest neighbor Cr interactions and Cs2Cu3ZrF12 to investigate strong geometrical frustration which leads to unusual magnetic phenomena.
NON-TECHNICAL SUMMARY:
The discovery and understanding of dilute magnetic semiconductors and frustrated magnets can advance the microelectronics and photonics industries, possibly leading to new devices based on spintronics. In addition, the members of the research group, which consists of high school students, undergraduate and graduate students, and postdoctoral associates will receive research training in the Science, Technology, Engineering and Mathematics (STEM) disciplines. Due to the demographics at The City College of New York (CCNY) of the City University of New York (CUNY), many female students and students from underrepresented ethnic groups will be trained in research. Multi-group meetings involving the chemistry and physics departments at CCNY will promote internal collaboration; a symposium for solid state chemistry in the New York City area will initiate communication and dissemination of results; and magnetic materials will be shared with other laboratories within the United States and around the world to pursue the understanding of the magnetic interactions. To further supplement the science and educational aspects, the local public will be introduced to crystal chemistry on open house days, science fairs and campus visitations by local high school groups.
