Cohn Lab

  

Transition-Metal Oxides

Research in our lab in recent years has focused on transport, magnetic, and dielectric properties of correlated-electron systems, particularly transition-metal oxides (TMOs) (magnetic, superconducting, and ferroelectric). We study materials in both bulk (polycrystalline, single-crystalline) and thin-film form (grown by pulsed laser deposition).

  • Low-Dimensional Materials
Bulk materials having reduced-dimensional electronic or magnetic properties have been the focus of attention for decades. Quasi-one-dimensional metallic systems tend to exhibit strongly-correlated electron behavior, manifest in electronic properties that deviate from those of traditional metals. Low-dimensional magnetic insulators can have a significant contribution to heat conduction from magnetic excitations even in the absence of a long-range magnetic ordered state.
  • Perovskite Manganites
Perovskite manganites have attracted much interest due to the complex interplay between lattice, charge, and spin interactions that give rise to phase diagrams rich in novel collective behavior. Ground states incorporating magnetic, charge and orbital order and ranging from insulating to metallic can be tuned during synthesis by chemical substitution that varies charge-carrier density and/or crystallographic structure. While most research in this large subfield has concentrated on Mn3+-rich (hole doped), FM compounds, our effort in the study of this class of materials has been primarily directed at lesser-studied Mn4+-rich (electron-doped) compounds derived from CaMnO3 and SrMnO3 by light doping with La or oxygen vacancies.
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  • Featured Articles

    Spin Seebeck Effect in Cu2OSeO3: Test of Bulk Magnon Spin-Current Theory. Akopyan, Prasai, Trump, Marcus, McQueen, and Cohn, Phys. Rev. B 101, 100407(R) (2020).

    Spin phases of the helimagnetic insulator Cu2OSeO3 probed by magnon heat conduction. Prasai, Akopyan, Trump, Marcus, Huang, McQueen, and Cohn, Phys. Rev. B 99, 020403(R) (2019).

    Ballistic magnon heat conduction and possible Poiseuille flow in the helimagnetic insulator Cu2OSeO3. Prasai, Trump, Marcus, Akopyan, Huang, McQueen, and Cohn, Phys. Rev. B 95, 224407 (2017) (Editor's Suggestion).

    Extreme Thermopower Anisotropy and Interchain Transport in the Quasi-One-Dimensional Metal Li0.9Mo6O17. Cohn, Moshfeghyeganeh, dos Santos, and Neumeier, Phys. Rev. Lett. 112, 186602 (2014).

    Giant Nernst Effect and Bipolarity in the Quasi-One-Dimensional Metal, Li0.9Mo6O17. Cohn, White, dos Santos, and Neumeier, Phys. Rev. Lett. 108, 056604 (2012).

    Giant Electrothermal Conductivity and Spin-phonon Coupling in an Antiferromagnetic Oxide. Chiorescu, Neumeier, and Cohn, Phys. Rev. Lett. 101, 257202 (2008).

    Impurity conduction and magnetic polarons in antiferromagnetic oxides. Chiorescu, Cohn, and Neumeier. Phys. Rev. B 76 020404(R) (2007).

    Polaron transport in the paramagnetic phase of electron-doped manganites. Cohn, Chiorescu, and Neumeier. Phys. Rev. B 72 024422 (2005).

    Low-temperature permittivity of insulating perovskite manganites. Cohn, Peterca, and Neumeier. Phys. Rev. B 70 214433 (2004).

    Heat conduction and magnetic phase behavior in electron-doped Ca1-xLaxMnO3 (0< x <0.2). Cohn and Neumeier. Phys. Rev. B 66, 100404 (2002).

    Possible signatures of magnetic phase segregation in electron-doped antiferromagnetic CaMnO3. Neumeier and Cohn. Phys. Rev. B 61, 14319 (2000).

    Hole localization in underdoped superconducting cuprates near 1/8 doping. Cohn, Popoviciu, Lin, and Chu. Phys. Rev. B 59, 3823 (1999).

    Glasslike Heat Conduction in High-Mobility Crystalline Semiconductors. Cohn, Nolas, Fessatidis, Metcalf, and Slack. Phys. Rev. Lett. 82, 779 (1999).

  • People

    Post-doctoral Fellows


    Former Lab Members

     

    Lab Member

    Dissertation Title

    Currently At

    Dharmendra Shukla

    Low-Temperature Thermal Conductivity in the Metal-Organic Frameworks (MOFs) [C(NH2)3][B(HCOO)3] (B = Cu2+, Zn2+,Ni2+)

    postdoc, Florida State Univ.

    Artem Akopyan

    Low-Temperature Spin Seebeck effect in the Helimagnetic Insulator Cu2OSeO3

    postdoc, Univ. Miami

    Narayan Prasai

    postdoc, 2015-2018

    Visiting Asst. Prof., St. Mary's College, MD

    Saeed Moshfeghyeganeh

    Anisotropic Transport Properties of Low-dimensional Molybdenum Bronzes

    postdoc, Fl. Int.'l Univ.

    Alexandra Cote

    undergrad, 2014-15

    physics graduate student, Univ. Illinois UC

    Narayan Prasai

    Spin-Phonon Coupling And Magnetic Heat Transport In Low-Dimensional Quantum Antiferromagnets (2015)

    postdoc, Univ. Miami

    Alwyn Rebello

    postdoc, 2013-14

    National University of Singapore

    Krishna Neupane

    Studies of the Insulator-Metal Transition in La1-xCaxMnO3 and Thin-Film Growth of Nd0.2Sr0.8MnO3 (2009)

    Corneliu Chiorescu

    Transport Studies of Lightly Electron-Doped Manganese Oxides (2008)

    Mihai Peterca

    M.S. Degree

    Editor, John Wiley and Sons

    Bartosz Zawilski

    postdoc

    Laboratoire Louis Neel, Grenoble

    Roland Maier

    Novel Phase of Thin-Film Iron-Doped Barium Titanate (2002)

    Gymnasium Instructor, Heidelberg, Germany

    Ciprian Popoviciu

    Thermal Transport and Phase Behavior of Cuprate Superconductors (1997)

    CISCO Systems

    Dmitri Litvinov

    University of Houston

  • Photos

  • Publications

    Mary O. Olagunju, Elsayed M. Zahran, Elnaz Zeynaloo, Dharmendra Shukla, Joshua L. Cohn, Bapurao Surnar, Shanta Dhar, Leonidas G. Bachas, and Marc R. Knecht, Design of Pd-Decorated SrTiO3/BiOBr Heterojunction Materials for Enhanced Visible-Light-Based Photocatalytic Reactivity, Langmuir 37, 11986 (2021). (Full Text PDF)

    Mary O. Olagunju, Elsayed M. Zahran, Jacqueline M. Reed, Elnaz Zeynaloo, Dharmendra Shukla, Joshua L. Cohn, Bapurao Surnar, Shanta Dhar, Leonidas G. Bachas, and Marc R. Knecht, Halide Effects in BiVO4/BiOX Heterostructures Decorated with Pd Nanoparticles for Photocatalytic Degradation of Rhodamine B as a Model Organic Pollutant, ACS Applied Nano Materials 4, 3262 (2021). (Full Text PDF)

    Ahmed E. ElMetwally, Elnaz Zeynaloo, Dharmendra Shukla, Bapurao Surnar, Shanta Dhar, Joshua L. Cohn, Marc R. Knecht, and Leonidas G. Bachas, Cu2O Cubes Decorated with Azine-Based Covalent Organic Framework Spheres and Pd Nanoparticles as Tandem Photocatalyst for Light-Driven Degradation of Chlorinated Biphenyls, ACS Applied Nano Materials 4, 2795 (2021). (Full Text PDF)

    Mary O. Olagunju, Xavier Poole, Patricia Blackwelder, Melonie P. Thomas, Beth S. Guiton, Dharmendra Shukla, Joshua L. Cohn, Bapurao Surnar, Shanta Dhar, Elsayed M. Zahran, Leonidas G. Bachas, and Marc R. Knecht, Size-Controlled SrTiO3 Nanoparticles Photodecorated with Pd Cocatalysts for Photocatalytic Organic Dye Degradation, ACS Applied Nano Materials 3, 4904 (2020). (Full Text PDF)

    D. S. Inosov, Y. O. Onykiienko, Y. V. Tymoshenko, A. Akopyan, D. Shukla, N. Prasai, M. Doerr, S. Zherlitsyn, D. Voneshen M. Boehm, V. Tsurkan, V. Felea, A. Loidl, and J. L. Cohn, Magnetic-field dependence of low-energy magnons, anisotropic heat conduction, and spontaneous relaxation of magnetic domains in the cubic helimagnet ZnCr2Se4, Physical Review B 102, 184431 (2020). (Full Text PDF)

    Mahamalage Kusumitha Perera, James D. Englehardt, Joshua L. Cohn, Edward A Dauer, Dharmendra Shukla, Electrohydromodulation for phosphate recovery from wastewater, Separation and Purification Technology 247, 116909 (2020). (Full Text PDF)

    A. Akopyan, N. Prasai, B. A. Trump, G. G. Marcus, T. M. McQueen, and J. L. Cohn, Spin Seebeck Effect in Cu2OSeO3: Test of Bulk Magnon Spin-Current Theory, Physical Review B 101, 100407(R) (2020). (Full Text PDF)

    D. Shukla, N. Prasai, T. M. Carlino, M. M. A. Mazza, A. M. Scott, and J. L. Cohn, Anisotropic Heat Conduction in the Metal Organic Framework Perovskites [C(NH2)3]X(HCOO)3 (X=Cu, Zn), Applied Physics Letters 114, 081907 (2019). (Full Text PDF)

    N. Prasai, A. Akopyan, B. A. Trump, G. G. Marcus, S. X. Huang, T. M. McQueen, and J. L. Cohn, Spin phases of the helimagnetic insulator Cu2OSeO3 probed by magnon heat conduction, Physical Review B 99, 020403(R) (2019). (Full Text PDF)

    D. C. Bell, C. J. Munro, J. M. Slocik, D. Shukla, A. D. Parab, J. Cohn, and M. Knecht, Biomimetic strategies to produce catalytically reactive CuS nanodisks, Nanoscale Advances 1, 2857-2865 (2019). (Full Text PDF)

    C. J. Munro, E. C. Bell, M. O. Olagunju, J. L. Cohn, E. M. Zahran, L. G. Bachas, and M. R. Knecht, Amino Acids for Sustainable Production of Cu2O Materials: Effects on Morphology and Photocatalytic Reactivity, ACS Sustainable Chemistry and Engineering 7, 17055-17064 (2019). (Full Text PDF)

    N. Prasai, A. B. Christian, J. J. Neumeier, and J. L. Cohn, Resonant scattering of phonons in the quasi-one-dimensional spin-chain compounds AB2O6 (A = Ni, Co; B = Sb, Ta) , Physical Review B 98, 134449 (2018). (Full Text PDF)

    N. Prasai, B. A. Trump, G. G. Marcus, A. Akopyan, S. X. Huang, T. M. McQueen, and J. L. Cohn, Ballistic magnon heat conduction and possible Poiseuille flow in the helimagnetic insulator Cu2OSeO3, Physical Review B 95, 224407 (2017). (Full Text PDF)

    S. Moshfeghyeganeh, A. N. Cote, J. J. Neumeier and J. L. Cohn, Anisotropic transport in the quasi-one-dimensional semiconductor Li0.33MoO3, J. Appl. Phys. 119, 095105 (2016). (Full Text PDF)

    S. H. Masunaga, A. Rebello, A. T. Schye, N.Prasai, J. J. Neumeier, and J. L. Cohn, Heat capacity, thermal expansion and heat transport in the Han Blue (BaCuSi4O10): Observation of structural phase transitions, J. Phys. Chem. Sol. 85, 69 (2015). (Full Text PDF)

    N. Prasai, A. Rebello, A. B. Christian, J. J. Neumeier, and J. L. Cohn, Phonon-spin scattering and magnetic heat transport in the quasi-one-dimensional spin-1/2 antiferromagnetic chain compound CuSb2O6, Physical Review B 91, 054403 (2015). (Full Text PDF)

    J. L. Cohn, S. Moshfeghyeganeh, C. A. M. dos Santos, and J. J. Neumeier, Extreme Thermopower Anisotropy and Interchain Transport in the Quasi-One- Dimensional metal Li0.9Mo6O17, Physical Review Letters 112, 186602 (2014). (Full Text PDF)

    J. L. Cohn, P. Boynton, J. S. Triviño, J. Trastoy, B. D. White, C. A. M. dos Santos, and J. J. Neumeier, Stoichiometry, structure, and transport in the quasi-one- dimensional metal Li0.9Mo6O17, Physical Review B 86, 195143 (2012). (Full Text PDF)

    E. J. Moon, J. M. Rondinelli, N. Prasai, B. A. Gray, M. Kareev, J. Chakhalian, and J. L. Cohn, Strain-controlled band engineering and self-doping in ultrathin LaNiO3 films, Physical Review B 85, 121106(R) (2012). (Full Text PDF)

    J. L.Cohn, B. D. White, C. A. M. dos Santos, and J. J. Neumeier, Giant Nernst Effect and Bipolarity in the Quasi-One-Dimensional Metal Li0.9Mo6O17, Physical Review Letters 108, 056604 (2012). (Full Text PDF)

    J. Chakhalian, J. M. Rondinelli, Jian Liu, B. A. Gray, M. Kareev, E. J. Moon, N. Prasai, J. L. Cohn, M. Varela, I. C. Tung, M. J. Bedzyk, S. G. Altendorf, F. Strigari, B. Dabrowski, L. H. Tjeng, P. J. Ryan, and J.W. Freeland, Asymmetric Orbital-Lattice Interactions in Ultrathin Correlated Oxide Films, Physical Review Letters 107, 116805 (2011). (Full Text PDF)

    A. de Campos, M. S. da Luz, C. A. M. dos Santos, A. T. Rice, A. M. Deml, B. D. White, J. J. Neumeier, and J. L. Cohn, Physical properties of quasi-one-dimensional SrNbO3.41 and Luttinger liquid analysis of electrical transport, Physical Review B 82, 125117 (2010). (Full Text PDF)

    K. Neupane, J. J. Neumeier, and J. L. Cohn, Anisotropic in-plane strain and transport in epitaxial Nd0.2Sr0.8MnO3 thin films, Journal of Applied Physics 106, 123904 (2009). (Full Text PDF)

    B. D. White, J. A. Souza, C. Chiorescu, J. J. Neumeier, and J. L. Cohn, Magnetic, transport, and thermodynamic properties of CaMn2O4 single crystals, Physical Review B 79, 104427 (2009). (Full Text PDF)

    C. Chiorescu, J. J. Neumeier, and J. L. Cohn, Giant Electrothermal Conductivity and Spin-Phonon Coupling in an Antiferromagnetic Oxide, Physical Review Letters 101, 257202 (2008). (Full Text PDF)

    C. Chiorescu, J. L. Cohn, and J. J. Neumeier, Impurity conduction and magnetic polarons in antiferromagnetic oxides, Physical Review B 76, 020404(R) (2007). (Full Text PDF)

    K. P. Neupane, J. L. Cohn, H. Terashita, and J. J. Neumeier, Doping dependence of polaron hopping energies in La1-xCaxMnO3 (0 < x < 0.15), Physical Review B 74, 144428 (2006). (Full Text PDF)

    M. A. Pires, C. Israel, W. Iwamoto, R. R. Urbano, O. Agüero, I. Torriani, C. Rettori, P. G. Pagliuso, L. Walmsley, Z. Le, J. L. Cohn, and S. B. Oseroff, Role of oxygen vacancies in the magnetic and dielectric properties of the high-dielectric-constant system CaCu3Ti4O12: An electron-spin resonance study, Physical Review B 73, 224404 (2006). (Full Text PDF)

    C. Chiorescu, J. J. Neumeier, and J. L. Cohn, Magnetic inhomogeneity and magnetotransport in electron-doped Ca1-xLaxMnO3 (0 < x < 0.10) Physical Review B 73, 014406 (2006). (Full Text PDF)

    J. L. Cohn, C. Chiorescu, and J. J. Neumeier, Polaron transport in the paramagnetic phase of electron-doped manganites, Physical Review B 72, 024422 (2005). (Full Text PDF)

    J. L. Cohn, M. Peterca, and J. J. Neumeier, Giant dielectric permittivity of electron-doped manganite thin films, Ca1-xLaxMnO3 (0<=x<=0.03), Journal of Applied Physics 97, 034102 (2005). (Full Text PDF)

    J. L. Cohn, M. Peterca, and J. J. Neumeier, Low-temperature permittivity of insulating perovskite manganites, Physical Review B 70, 214433 (2004). (Full Text PDF)

    G.S. Nolas, J.L. Cohn, J. S. Dyck, C. Uher, G. A. Lamberton, Jr., and T.M. Tritt, Low temperature transport properties of polycrystalline Ba8Ga16Sn30 Journal of Materials Research 19, 3556 (2004).

    R. Maier and J. L. Cohn, Ferroelectric and ferrimagnetic iron-doped thin-film BaTiO3: Influence of iron on physical properties, Journal of Applied Physics 92, 5429 (2002). (Full Text PDF)

    J. L. Cohn and J. J. Neumeier, Heat conduction and magnetic phase behavior in electron-doped Ca1-xLaxMnO3 (0< x <0.2), Physical Review B 66, 100404(R) (2002). (Full Text PDF)

    G. S. Nolas, D. G. Vanderveer, A. P. Wilkinson, and J. L. Cohn, Temperature dependent structural and transport properties of the type II clathrates A8Na16E136 (A = Cs or Rb and E = Ge or Si), Journal of Applied Physics 91, 8970 (2002). (Full Text PDF)

    G. S. Nolas, J. L. Cohn, J. S. Dyck, C. Uher, and J. Yang Transport properties of polycrystalline type-I Sn clathrates, Physical Review B 65, 165201 (2002). (Full Text PDF)

    R. Maier, J. L. Cohn, J. J. Neumeier, and L. A. Bendersky, Ferroelectricity and ferrimagnetism in iron-doped BaTiO3, Applied Physics Letters 78, 2356 (2001). (Full Text PDF)

    J. J. Neumeier and J. L. Cohn, Possible signatures of magnetic phase segregation in electron-doped antiferromagnetic CaMnO3, Physical Review B 61, 14319 (2000). (Full Text PDF)

    J. L. Cohn, Electrical and Thermal Transport in Perovskite Manganites, Journal of Superconductivity: Incorporating Novel Magnetism 13, 291 (2000). (Full Text PDF)

    J. L. Cohn, Heat Conduction and Charge Ordering in Perovskite Manganites, Nickelates and Cuprates, Thermal Conductivity 25, Thermal Expansion 13, ed. by C. Uher and D. T. Morelli, (Technomic Publishing, Lancaster, PA, 2000), pp. 87-97.

    L. A. Bendersky, R. Maier, J. L. Cohn, and J. J. Neumeier, Structural studies of pulsed-laser-deposited Ba4Fe4Ti3O16 oxide films, Journal of Materials Research 15, 1389 (2000).

    G. S. Nolas, T. J. Weakley, J. L. Cohn, and R. Sharma, Structural properties and thermal conductivity of crystalline Ge clathrates, Physical Review B 61, 3845 (2000). (Full Text PDF)


    Selection of Papers Prior to 2000

    1. J. L. Cohn, C. P. Popoviciu, Q. M. Lin, and C. W. Chu, Structural, chemical and transport properties of a new clathrate compound: Cs8Zn4Sn42, Chemistry of Materials 1, 2470 (1999). (Full Text PDF)
    2. J. L. Cohn, G. S. Nolas, V. Fessatidis, T. H. Metcalf, and G. A. Slack, Glasslike Heat Conduction in High-Mobility Crystalline Semiconductors, Physical Review Letters 82, 779 (1999). (Full Text PDF)
    3. J. L. Cohn, C. P. Popoviciu, Q. M. Lin, and C. W. Chu, Hole localization in underdoped superconducting cuprates near 1/8 doping, Physical Review B 59, 3823 (1999). (Full Text PDF)
    4. J. L. Cohn, G. S. Nolas, V. Fessatidis, T. H. Metcalf, and G. A. Slack, Thermal Transport as a Probe of Localized Charge and Lattice Distortions in Manganites and Cuprates, Journal of Superconductivity 12, 281 (1999). (Full Text PDF)
    5. G. S. Nolas, J. L. Cohn, G. A. Slack, and S. B. Schujman, Semiconducting Ge clathrates: Promising candidates for thermoelectric applications, Applied Physics Letters 73, 178 (1998). (Full Text PDF)
    6. J. L. Cohn and J. Karpinski, Anisotropic in-plane thermal conductivity of single-crystal YBa2Cu4O8, Physical Review B 58, 14617 (1998). (Full Text PDF)
    7. G. S. Nolas, J. L. Cohn, and G. A. Slack, Effect of partial void filling on the lattice thermal conductivity of skutterudites, Physical Review B 58, 164 (1998). (Full Text PDF)
    8. J. L. Cohn, J. J. Neumeier, C. P. Popoviciu, K. J. McClellan, and Th. Leventouri, Local lattice distortions and thermal transport in perovskite manganites, Physical Review B 56, R8495 (1997). (Full Text PDF)
    9. C. P. Popoviciu and J. L. Cohn, Thermal transport in YBa2Cu3O6+x: Doping dependence across the phase diagram, Physical Review B 55, 3155 (1997). (Full Text PDF)
    10. S. E. Barnes, J. L. Cohn, and F. Zuo, The Possibility of Flux Flow Spectroscopy, Physical Review Letters 77, 3252 (1996). (Full Text PDF)
    11. Joshua L. Cohn, Superconducting-state enhancement of thermal conductivity in the cuprates: Correlation with the pair density, Physical Review B 53, R2963 (1996). (Full Text PDF)
    12. J. L. Cohn, C. K. Lowe-Ma, and T. A. Vanderah, Anomalous phonon damping and thermal conductivity in insulating cuprates, Physical Review B 52, R13134 (1995). (Full Text PDF)

  • Contact Information

    Joshua L. Cohn
    jcohn@miami.edu

    Department of Physics
    309 Knight Physics Bldg., University of Miami
    Coral Gables, FL 33124-5630
    (305) 284-7123

     

    Lab:

    Knight Physics Bldg.

    Room 123
    University of Miami
    Coral Gables, FL 33146
    Ph: (305) 284-7135
    FAX: (305) 284-4222