RUI: Pressure And Chemical Modulation Of Nanoscale Magnetic Interactions In Metal-Organic Polymers

Eastern Washington University, Cheney WA

Investigators

Abstract

****NON-TECHNICAL ABSTRACT**** Superconductors, materials which conduct electricity without any loss due to resistance, have the potential to revolutionize the energy demands of our society in the future. However, scientists need to increase the working temperatures of the superconductors in order for them to be useful. Despite much study, in many instances the mechanism behind the superconducting behavior remains a mystery. In an attempt to develop a better understanding of their complex behaviors, this award supports a project aiming to synthesize and characterize molecular materials that mimic the magnetic properties of oxide and pnictide superconductors, two classes of superconductors that may work at higher temperatures. The challenge in directly studying such systems lies in the large magnetic interactions that exist between the magnetic sites they contained. Through a variety of chemical methods, attempts will be made to reduce the scale of these interactions by controlling the molecular assembly of model compounds using particular combinations of chemical bonds. This structural control will enable a systematic approach to vary distances between atoms, the number of magnetically-active electrons, and other properties of the material. The application of pressure may lead to other unusual discoveries. The materials discovery effort will be complemented by extensive characterization and theoretical work. The highly collaborative nature of this project makes use of several national and international user facilities and will provide unique opportunities for the undergraduate students to travel to facilities to participate in the experiments, as well as to attend professional conferences. Undergraduate student involvement in every aspect of the project will stimulate the students? growth and enthusiasm as young scientists, as well as provide them with the necessary background to begin graduate work in the future or to go on to careers in the physical sciences. This research project receives support from the Division of Materials Research and the Chemistry Division. ****TECHNICAL ABSTRACT**** This award to a Predominately Undergraduate Institution will support research focusing on the design, synthesis, and characterization of low-dimensional (1- and 2D) quantum magnets, in particular square lattices, as they may mimic the structural and magnetic properties of analogous cuprate and iron-pnictide superconductors. Using specific combinations of coordinate covalent bonds and strong hydrogen bonds, the molecular positioning of components will be controlled and tuned and the magnitude/sign of the intralayer (J) and interlayer (J') magnetic interactions and their relative ratio (J'/J) will be systematically varied. The magnetic tunability of the systems will be achieved by: (a) ion-exchange (either positive or negative), (b) chemical doping, (c) application of hydrostatic or chemical pressure (i.e., isotopic substitution) and (d) co-ligand variation. Control of inter- and intralayer couplings will enable the modulation of the exchange anisotropy, critical temperatures (TN), and critical magnetic fields (Bc). In addition, the single-ion anisotropy in these systems will be manipulated by modifying the spin quantum number. The materials discovery effort will be complemented by extensive characterization and theoretical work. Magnetic-field and/or pressure-induced quantum criticality may lead to unusual phases, such that abrupt changes in behavior can occur due to instabilities in the magnetic system which ultimately drive phase transitions. Undergraduate student involvement in every facet of the project will stimulate their growth and enthusiasm as young scientists, as well as provide them with the necessary background to begin graduate work in the future or to go on to careers in the physical sciences. This research project receives support from the Division of Materials Research and the Chemistry Division.