Center for Advanced Materials (CAM) PI: Gang Cao, University of Kentucky Co-PIs: Joseph W. Brill, University of Kentucky William P. Crummett, Centre College Lance E. DeLong, University of Kentucky William R.Grisé, Morehead State University Bruce J. Hinds, University of Kentucky Amer Lahamer, Berea College Kwok-Wai Ng, University of Kentucky Sean Parkin, University of Kentucky CAM New Hires: Beth Guiton, Ribhu Kaul and Doug Strachan, University of Kentucky Other participating faculty members: Y.T. Cheng, Richard Eitel, Todd Hastings and Haluk Karaca, University of Kentucky Outlook of the Center Center for Advanced Materials as a multidisciplinary research institution is to design, synthesize and characterize novel electronic materials in either single crystal or thin-film form. (Currently, we focus on single crystal oxides, multilayer films, inorganic/organic hybrid systems and single-molecule magnets.) It is widely recognized that whoever controls the synthesis and discovery of novel materials controls technologies. The CAM is timely especially when the traditional U.S. leadership in materials research has eroded in recent years due in part to the lack of scientists who possess skills in both the synthesis and characterization of new materials The CAM will create complementary expertise and facilities that will optimize the proposed program The CAM will generate synergies and funding opportunities to initiate new materials research efforts among several colleges and universities in the Commonwealth and National Laboratories. In summary, the scope of CAM research can be aggressively expanded to explore emerging or unanticipated research topics and interdisciplinary areas, and will eventually have experimental, theoretical, and computational components. The CAM will pursue research grants from Federal and private funding agencies, and will fund promising, high-risk projects to facilitate the preparation of major grant proposals for external funding. Highlights of Year 1 (2008-2009) CAM New Faculty Hires: Doug Strachan (CMP Exp), Rubhul Kaul (CMP Theory) and Beth Guiton (Solid State Chemistry). CAM New Faculty Lab: Strachen’s lab is being built. CAM Infrastructure: A Linde’s helium liquefier, a central piece of CAM equipment, is being installed in UK Chem-Phys building. The installation is expected to be complete in September, 2009. CAM Space: CAM will be located in UK Chem-Phys Building. Omni Architects is designing CAM lab space. The renovation funded by UK will start in summer, 2010. CAM at Centre College: A closed-cycle displex cryostat operating from 4 K to 400 K is built for measurements of ferroelectric properties in co-PI Crummett lab. CAM RAs: Four graduate students are supported by CAM via UK match CAM Seminar: The CAM Seminars are given by distinguished scientists working in areas of materials physics, chemistry and engineering. The Kickoff Seminar was held on February 6, 2009 International Workshop: The 2nd Workshop on Novel Electronic Materials, University of Kentucky, May 14-17, 2008, Highlight of Year 1 (2008-2009) CAM Research: It covers a wide spectrum of materials and experimental probes, such as bulk spin-valve effect, giant magneto- electric effect, pnictide superconductors, novel phenomena in charge density waves, new ferromagnetic semiconductor, design and construction of a two dimensional piezoelectric micro-positioner, etc. Publications, New Grants, Awards, etc (incomplete) *6 papers published or submitted * 3 invited talks at major international conferences (including APS March Meeting) * 1 NSF grant and 1 DoE grant *UK 2009-2010 University Research Professor Award Strachan Lab Strachan Lab Helium Liquefier Being Installed CAM Layout (First Floor in Chem-Phys Building, ~1850 sq ft) CAM Crummett Lab at Centre College Center for Advanced Materials Kick-off Seminar Insulator to Correlated-Metal Transition in doped VO2 Robert J. Cava Princeton University Friday, February 6, 2009 at 3:30 PM (Refreshments in CP-137 at 3:00 PM) Chem-Phys Building CP-139 (Chemistry Auditorium) Abstract : Materials that should be metallic conductors by simple electron counting and yet are electrical insulators have been of interest for decades as embodiments of strong electron-electron and electron-lattice interactions in solids. Among the most iconic of such materials is Rutile structure VO2, a 3d1 compound whose crystal structure is based on chains of edge-sharing VO6 octahedra. VO2 undergoes a structural distortion that creates V-V pairs along the chains when it is cooled through its metal to insulator transition. The V-V pairs localize the a 3d1 electrons in spin singlets. First addressed in the 1970s, the current understanding is that neither of the most common scenarios – the Mott state, in which Coulombic repulsion between electrons attempting to occupy the same site introduces an energy gap, or the Peierls state, in which electrons on neighboring sites form localized spin singlets and metal-metal pairs – is alone sufficient to explain VO2 ’s electronic properties. In this talk, I will describe the electronic and magnetic properties of the V1-xMox O2 solid solution. The Mo doping of VO2 , which introduces electrons, first results in the formation of localized magnetic states, due to breaking up the spin singlets and releasing their moments. These localized states then hybridize on continued doping to form an intermediate mass metal with substantial remnant magnetic character. The results will be discussed in the context of the literature on metal-insulator transitions in solids. The 2nd Workshop on Novel Electronic Materials University of Kentucky, May 14-17, 2008 Novel Spin-Valve Effect in Bulk Single Crystal Ca3(Ru,Cr)2O7 (Cao Group) 30 3 B || a [ (B)- (0)]/ (0) (%) c b (a) (b) 20 M B C2 x = 0.17 2 c B Mb (B/f.u.) Ru-O 10 T = 40 K C1 Ca-O Ru-O c 0 c Ru-O 1nm Soft Ca-O 1 b Cr-O Ca-O c -10 Ca-O Ru-O b Hard Ru-O a -20 0 0 1 2 3 4 5 6 7 B (T) Due to different coercivities, the switching of the magnetic layers occurs at different magnetic fields, providing a change in the relative orientation of the magnetizations, thus spin-valve effect Technological potential: magnetic sensors, read-heads for hard drives, etc GC et al PRL, 2008 Giant Magneto-electric Effect in Sr2IrO4 (Cao Group) 0 50 100 150 200 250 300 120 0.06 400 0.04 (a) T=50 K Dielectric Constant ' [ '(H)- '(0)/ '(0)] (%) (a) 100 kHz 0.05 c 100 M (1.7K) 300 c 0.03 80 0.04 M ( /Ir) c 600 kHz H c M( /Ir) c 500 kHz 60 H||c-axis 0.03 200 B 150 kHz M (0.1T) 0.02 B c a 100 kHz 40 0.02 M (0.2T) T=110 K 100 c 0.01 10 kHz 20 100 kHz 0.01 c T M 500 kHz 0 0 0 0 0 2 4 6 8 10 0.3 O O 100 kHz H (T) o 0.2 Ir Ir 500 kHz 1/ ' 0.03 c Ir Ir 110 K (b) M ( /Ir) 0.1 (b) I II 0.02 B IrO6 octahedra 00 50 100 150 200 250 300 0.01 5K c T(K) 50 K c-axis 0 80 K 0 0.5 H (T) 1 1.5 o The figures show strong coupling between magnetization and dielectric properties Technological potential: magnetic field sensors, information storage, etc. Magnetic Field Dependence of Specific Heat of LaFeAsO (Brill Group) We studied the specific heat of pnictide superconductors and 10.0 their undoped precursors. LaFeAsO 9.5 Shown here is shown the specific heat of the undoped parent cP / R compound, LaFeAsO near its 9.0 magnetic and structural phase Tstruc transitions. The field B=0 8.5 independence of the magnetic Tmag B = 11 T transition temperature (Tmag) suggests that the magnetic 8.0 120 130 140 150 160 170 180 ordering is for very anisotropically coupled local moments, rather T (K) than itinerant (spin-density-wave) electrons, as usually assumed 66 64 PrFeAsO Voltage Induced Torsional Strain in TaS3 (Brill Group) We have studied the dynamics of “voltage-induced torsional strain” (VITS) in the charge-density-wave conductor (CDW), TaS3. Shown here are hysteresis loops in the torsional strain (i.e. twist angle, approximately 1o) as functions of frequency traversing the loop (at T = 77 K). For transit times less than ~ 10 s, the strain does not fully develop. We have also found that he strain begins at a voltage below the threshold at which the CDW becomes depinned, suggesting that the VITS is not caused by CDW current but by polarization of the CDW interacting with defects in the lattice. Single-Crystal H II ab-plane T2 = 171 K 0.025 ZFC BaMn2.49Ru3.51O11 T3 = 128 K (De Long Group) 0.020 Three magnetization anomalies m (emu/g) 0.015 signal competing FM and AFM 0.010 correlations, magnetic frustration T1 = 183 K within Kagomé plane. 0.005 Few frustrated systems are available 0.000 0 50 100 150 200 250 in single crystals. T (K) Little is known about PT in 2.0 0.01 T disordered Kagomé lattices of spins 0.05 T 0.1 T S > ½. Here, Mn is S = 2. 1.5 (emu/mole) 0.5 T FM correlations: 171 < T < 183 K 1T 1.0 AFM correlations: 128 < T < 171 K 0.5 FM correlations: T < 128 K In-plane H destroys AFM peak. 0.0 0 50 100 150 200 250 T(K) Nanoscience: Design and construction of a two dimensional piezoelectric micro-positioner (Ng Group) F y z x F Schematic diagram showing principle of operation. Viewing the motion of the micro-positioner under a microscope. The micropositioner. The scanner of the STM will be installed inside one of the tube. Planned Activities in Year 2 (2010-2011) CAM New Faculty Hire: We plan on hiring either a thin-film or neutron scattering expert to fill the fourth faculty position. CAM Infrastructure: (1) Operate the helium liquefier and the helium recovery system. (2) Purchase and install a 14 T magnet system for a wide range of measurements at ultralow temperatures (mK) (Quantum Design PPMS). (3) Renovate the CAM space and move in. CAM Summer Internships: 5 undergraduate students will work in PIs’ labs CAM International Workshop: The 3rd Workshop on Novel Electronic Materials (the 2nd Workshop held at UK in May 15-17, 2008 drew more than 80 leading scientists from the US and around world) CAM RAs: Pursue more funding to support more graduate students (besides the UK match for 4 graduate students) CAM Seminar: The monthly seminar is given by distinguished scientists world wide. Goals and Milestones in 2011-2012 and Beyond Install 18/20 T magnet with ultralow temperatures and high pressure functions x-ray diffractometer with variable temperature stage, pressure cell and magnetic field Submit major research and education proposals to funding agencies for programs such as MRSEC or IGERT at NSF Implement the new courses and program for graduate students. Summer program for high school science teachers and students. Develop a user program and encourage external scientists to use the CAM facilities as well as collaborate with CAM scientists Develop a visitor program that sponsors two Distinguished Scientists for a six-month visit to the CAM each year Develop devices using materials developed at the CAM Identify and transfer technologies developed at the CAM Establish broad and productive collaborations or partnerships with national labs as a leading materials institution in the nation. Management, Evaluation and Assessment The progress of each participant will be reviewed by the Executive Committee before the Annual Meeting. The Executive Committee will prepare a summary of activities of the year as well as the budget for the next year. Each PI will receive a written evaluation of his or her progress and proposal, including a statement of funds to be allocated during the next year. We will also solicit new proposals from the Faculty. We will support a part-time Administrative Assistant to the Director, responsible for all budgetary issues, reports and publications. An External Advisory Committee consisting of three prominent scientists, selected for their academic accomplishments, international recognition and administrative experience, will evaluate all research and educational activities of the Center. The External Advisory Committee will conduct a site visit each year, review the summary annual reports, and provide feedback to the Executive Committee. The evaluation for each PI and the CAM as a whole will be based upon the following criteria: (1) Publications, invited talks, patents and other recognition (2) Individual research grants sought and awarded (3) Collaborative research among the PI’s and with external scientists (4) Graduate student research, fellowships awarded, and other recognition (5) Undergraduate research, summer internships, publications involving undergraduate students (6) Other outreach activities with local schools and industrial contacts (7) Efforts contributed to enhancing CAM facilities (8) Interpersonal relations and team work.
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