Materials

Document Sample
Materials Powered By Docstoc
					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.

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:6
posted:8/11/2011
language:English
pages:24