Functional Inorganic Materials at UMD
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July 2016 Congratulations to Dan for winning the Margeret C. Etter Student Lecturer Award in Powder Diffraction. Left, Dan receiving his award from Dr. Ashfia Huq (SNS, Oak Ridge National Labs).
July 2016 Congratulations to Amber for winning the Margeret C. Etter Student Lecturer Award in Neutron Scattering. Right, Amber receiving her award from Prof. Branton Campbell (BYU Physics).
June 2016 Our article on the superconductors (Li1-xFexOH)FeSe was selected as a Hot Paper and for the backcover of a special edition of the Journal of Materials Chemistry C. The issue was on Emerging Investigators 2016: Novel design strategies for new functional materials..
Research area 1: Late transition metal chalcogenides for superconductivity and "Hund metallicity"
Our goal is to prepare new two-dimensional and three-dimensional chalcogenides of the late transition metals (iron, cobalt, and nickel) for manipulating charge, spin, and orbital degrees of freedom. In all of our compounds, we are focused on materials that are either metallic or semimetallic, and where some d-orbitals exhibit localized behavior while others itinerant. Hund's coupling between the two sets leads to a new way of understanding magnetism in these metals. In all of these chalcogenides, the M2+ ions are in tetrahedral coordination, and those MCh4 tetrahedra are edge-sharing. For the 2D materials, we are primarily interested in how to build new heterestructures to manipualte the magnetism and superoconductivity. For the 3D materials, we are interested in the fundamental interactions between the magnetism and itinerant electrons. In all cases, we are looking to find new synthetic routes towards new materials and single crystal growth. (Click here) to see our our latest papers on these materials. Below, a schematic of the topochemical reactions to achieve different phases of layered iron chalcogenides.
Research area 2:Mixed-valence microporous oxides for novel magnetism and energy-related applications
Our goal is to prepare new metal oxides with microporous and mesoporous structures, some of which are known from naturally occurring minerals such as hollandite and todorokite. The 1D channels are constructed purely of edge-sharing MO6 octahedra where M is a transition metal and cations such as K+ and Ba2+ reside in those channels. We have focused on Mn-based oxides for magnetic properties, Ti-based oxides for catalytic and energy storage applications, and V-based oxides for electrical transport properties such as metal-to-insulator transitions. The hollandite-type structure is especially versastile and can readily accomodate several members of the transition metal series, which allows for facile doping to tune the electronic and magnetic properties. Click here to see our our latest paper on titanate holldandites and here for the Mn-based hollandites. Below, a schematic demonstrating the various structurally-related transition metal oxides possible in this family of compounds.
Research area 3: Anion manipulation of transition metal oxides and in-situ neutron and X-ray diffraction studies
Our goal is to perform soft chemistry on oxides to manipulate their anionic structure. Ultimately, we would like to understand the criteria that leads to either anion substitution or complete anion removal such as reductive de-intercalation with electropositive metal hydrides. We perform in-situ studies with X-rays and neutrons to understand these topotactic reactions. Potential applications include chemical looping cycles for combustion of fuels and tuning of magnetic properties via anion manipulation as opposed to cation substitution. Below, a schematic of a a chemical looping reaction involving a perovskite oxide and the the in-situ synchrotron diffraction with patterns collected every 6 seconds.
Research area 4: Uncovering Ferrotoroidic Ordering through Targeted Materials Synthesis and Polarized Neutron Diffraction
Our goal is to prepare and study the magneto-structural properties of what have been considered the missing fourth class of primary ferroics--ferrotoroidics. In these materials, the magnetic space groups allow simultaneous magnetic ordering and electric polarization, i.e. breaking both time-reversal and space-inversion symmetries. In addition, the spins of the magnetic moments in the crystal lattice arranged head-to-tail, which induces a perpendicular toroidal moment. Since this toroidization produces ferroic domains, ferrotoroidicity is consequently considered a primary ferroic order. Our work is to explore the materials that exhibit ferrotoroidicity by synthesizing those that possess the required symmetries and magneto-electric properties, and developing the polarized neutron diffraction instrumentation needed to elucidate this type of order.