Aling Michael - EUREKA Poster - 2

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Transcript of Aling Michael - EUREKA Poster - 2

  • TNel

    TMIT

    Abhijit Biswas, et al. 4

    The unintended height of a

    crystal placed in a powder x-

    ray diffractometer shifts

    the Bragg peak locations3:

    2 c sin H

    Rcos = L

    x = 0x = 0.34

    where H is the height offset and R is the diffractometer radius.

    Two samples

    peaks differing at

    the (00L)-type

    peak 0010

    Motivation

    Magnetic and Electronic Transitions in a Highly-Doped Mott InsulatorMichael Aling, Dr. Julian Schmehr, Prof. Stephen D. Wilson

    UCSB Department of Materials

    It is hoped that this study will reveal new

    phases in an electronically-useful material.

    Cousins of this Ruddlesden-Popper ruthenium-

    doped strontium iridate become superconducting at

    low temperatures, while also exhibiting other rich

    physical phenomena: fermi liquid ground states,

    metamagnetism, colossal magnetoresistance, and

    multiple electronic transitions. Sr3Ir2O7s relation to

    cuprate high-temperature superconductors is

    further motivation for study.1

    The Parent Compounds Previous Work1

    Continuing and Future Work

    Doping Sr3(Ir1-xRux)2O7

    References

    Identifying Electronic & Magnetic Phases

    Unusual percolative phase transitions in

    Sr3(Ir1-xRux)2O7 impact properties:

    300

    10000

    Tem

    pera

    ture

    (K

    )

    Ru level (%)

    *

    Interaction strengthens AF order

    when it would otherwise die off (*)

    Cro

    ss sectio

    n sch

    em

    atic

    (a single

    crystal)

    Adapting x-ray diffraction to save time and preserve samples

    Paramagnetism

    (PM)

    Antiferromagnetism

    (AF)

    Resistivity Analysis Reveals TransitionsStudying little-known region: 40% to 60% Ru

    (Will add error bars)(Should also add powder points)

    Sr3Ir2O7 (327), a Mott insulator, has a smaller

    bandgap than its 214 cousin, making it an ideal

    candidate to be doped in order to probe the

    combination of crystal field splitting, spin-orbit

    coupling, and small Coulomb interaction which

    together make it insulating.1, 2 Sr3Ru2O7 is a metal

    with paramagnetic disorder (contrasting the iridates

    low-temperature antiferromagnetism) near a

    magnetic instability.1

    No transitions observed

    at x=0.62

    Progress on Phase

    Diagram

    When this material

    becomes metallic,

    it is only because a

    network of

    metallic pockets

    begins to join

    (percolative

    threshold.) In

    both the insulating

    and metallic

    regimes, regions of

    both phases

    coexist on a

    nanometer scale.

    Utilizing Lattice Parameter Contraction

    Dopant Distribution in Growths(Each point represents one crystal)

    About 5 samples found in desired range, across 3 growths

    Dopant level varies greatly in flux

    growths. X-ray diffraction (XRD)

    is faster and less costly than

    EDX (energy-dispersive x-ray

    spectroscopy). While EDX

    directly analyzes concentrations,

    this technique offers an indirect

    method.

    Nonlinearity caused by

    pull of competing

    nanometer-scale

    regions

    A MATLAB program translates

    information about peak location into

    the lattice parameter c by solving the system numerically.

    The results from this single-crystal

    method are as accurate as powder

    results from the previous study.

    Lattice Parameter by Dopant Level(Each point represents one sample)

    Tem

    pera

    ture

    (K

    )M

    etal

    -in

    sula

    tor

    Mag

    net

    ic

    Lattice Parameter Solver

    The MATLAB program will be

    expanded into a full Rietveld

    refinement capable of overcoming

    the primary challenge associated

    with a single-crystal technique:

    resolving peak splitting due to

    uneven crystal surfaces. Human

    error will also be reduced by the

    further automation of the process.

    After first completing the survey of

    the x=0.4 to 0.6 region by gathering

    heat capacity, magnetization, and

    sub-Kelvin resistivity (temperatures

    at which cousin compounds become

    superconducting), further growths

    focused around x=0.75 will push

    forward into a regime even less-

    studied.

    People

    Michael Aling

    Sophomore

    Mechanical Engineering

    Julian Schmehr

    Postdoctoral Scholar

    Materials Science

    Stephen D. Wilson

    Principal Investigator

    Materials Science

    1. Dhital, C. et al. Carrier localization and electronic phase separation in a

    doped spin-orbit-driven Mott phase in Sr3(Ir1-xRux)2O7. Nat. Commun.

    (2014).

    2. Dhital, C. et al. Spin ordering and electronic texture in the bilayer iridate

    Sr3(Ir1-xRux)2O7. Physical Review B 86, 100401(R) (2012).

    3. Jesche, A. et al. X-Ray diffraction on large single crystals using a powder

    diffractometer. Philosophical Magazine (2016).

    4. Abhijit Biswas, Ki-Seok Kim and Yoon Hee Jeong (2016). MetalInsulator

    Transitions and Non-Fermi Liquid Behaviors in 5d Perovskite Iridates,

    Perovskite Materials - Synthesis, Characterisation, Properties, and

    Applications, Dr. Likun Pan (Ed.), InTech, DOI: 10.5772/61285.

    Both adapted from 1

    Supported by NSF CAREER-Award DMR-1056625