Dr. Michael Graf
associate chairperson and professor of physics
Office: Higgins Hall 230B
Lab: Higgins Hall 110
Ph.D., Physics, Brown University
B.S., Physics/Math minor, Rensselaer Polytechnic Institute
My current research focuses mainly on magnetism and spin dynamics in correlated electronic systems, and properties of Bi nanowires. Primary experimental techniques include bulk probes such as thermal measurements, electronic transport, and magnetization, and the local probe technique of muon spin spectroscopy (µSR). Recent collaborative efforts involve colleagues at the Paul Scherrer Institute (Switzerland), ISIS Muon Facility (UK), University of California at Santa Barbara, Nehru Centre for Advanced Scientific Research (India), Cardiff University (UK), and the University of Pavia (Italy).
Studies include correlation effects and magnetic frustration in complex iridate oxides (Na4Ir3O8, A2Ir2O7, A = Y or a lanthanide), spin dynamics and onset of correlations in single ion magnets (LiY1-xHoxF4) and single molecule magnets (LnPc2, Ln = lanthanide and Pc = phthalocyaninato complex), and the characterization of surface states in Bi nanowires.
My lab facilities include 3He and dilution refrigerators equipped with 9 and 8 T superconducting magnets, respectively, and a Quantum Design Evercool Magnetic Properties Measurement System. I am also a regular user of muon beam facilities in Switzerland and the UK.
Short-Range Correlations in the Magnetic Ground State of Na4Ir3O8 , R. Dally, T. Hogan, A. Amato, H. Leutkens, C. Baines, J. Rodriguez-Rivera, M. J. Graf, and S. D. Wilson, Phys. Rev. Lett. 113, 247601 (2014).
Magnetization and Hall effect studies on the pyrochlore iridate Nd2Ir2O7 , S. M. Disseler, S. R. Giblin, C. Dhital, K. C. Lukas, S. D. Wilson, and M. J. Graf, Phys. Rev. B 87, 060403 (Rapid) (2013).
Magnetic Order in the Pyrochlore Iridates A2Ir2O7 (A = Y, Yb), S. M. Disseler, C. Dhital, A. Amato, S. R. Giblin, C. de la Cruz, S. D. Wilson, and M. J. Graf, Phys. Rev. B 86, 014428 (2012).
Evolution of spin relaxation processes in LiY1-xHoxF4 with increasing x studied via ac-susceptibility and muon spin relaxation, R. C. Johnson, B. Z. Malkin, J. S. Lord, S. R. Giblin, A. Amato, C. Baines, A. Lascialfari, B. Barbara, and M. J. Graf, Phys. Rev. B 86, 014427 (2012).
Magnetic order and the electronic ground state in the pyrochlore iridate Nd2Ir2O7 , S. M. Disseler, C. Dhital, T. C. Hogan, A. Amato, S. R. Giblin, C. de la Cruz, A. Daoud-Aladine, S. D. Wilson, and M. J. Graf, Phys. Rev. B 85, 174441 (2012).
Thermoelectric prospects of nanomaterials with spin-orbit surface bands, T. E. Huber, K. Owusu, S. Johnson, A. Nikolaeva, L. Konopko, R. C. Johnson, and M. J. Graf, J. Appl. Phys. 111, 043709 (2012)
Competing interactions and magnetic frustration in Yb4LiGe4 , S. M. Disseler, J. N. Svensson, S. C. Peter, C. P. Byers, C. Baines, A. Amato, S. R. Giblin, P. Carretta, and M. J. Graf , Phys. Rev. B 84, 174429 (2011).
µSR study of spin dynamics in LiY1-xHoxF4 , R. C. Johnson, K. H. Chen, S. R. Giblin, J. S. Lord, A. Amato, C. Baines, B. Barbara, B. Z. Malkin, and M. J. Graf, Phys. Rev. B 83, 174440 (2011).
Surface state band mobility and thermopower in semiconducting bismuth nanowires, T. E. Huber, A. Adeyeye, A. Nikolaeva, L. Konopko, R. C. Johnson, and M. J. Graf, Rev. B 83, 235414 (2011).
Spin and charge dynamics in [TbPc2]0 and [DyPc2]0 single-molecule magnets, F. Branzoli, P. Carretta, M. Filibian, M. J. Graf, S. Klyatskaya, M. Ruben, F. Coneri, and P. Dhakal, Physical Review B 82, 134401 (2010).
Observation of three-dimensional behavior in surface states of bismuth nanowires and the evidence for bulk-Bi surface quasiparticles, T.E. Huber, A. Nikolaeva, L. Konopko, and M.J. Graf, Phys. Rev. B 79, 201304 (Rapid) (2009).
Spin Dynamics in the Negatively Charged Terbium(III) bis-Phthalocyaninato Complex, F. Branzoli, P. Carretta, M. Filibian, G. Zoppellaro, M. J. Graf, J. R. Galan-Mascaros, O. Fuhr, S. Brink, and M. Ruben, J. Am. Chem. Soc. 131, 4387 (2009).
19F nuclear spin relaxation and spin diffusion effects in the single ion magnet LiYF4:Ho3+, B.Z. Malkin, M.V. Vanyunin, M. J. Graf, J. Lago, F. Borsa, A. Lascialfari, A.M. Tkachuk, B. Barbara, European Physical Journal B 66, 155 (2008).
Role of boundary roughness in the electronic transport of Bi nanowires, T. E. Huber, A. Nikolaeva, D. Gitsu , L. Konopko , and M. J. Graf, J. Appl. Phys. 104, 123704 (2008).
Muon Spin Rotation Studies of Spin Dynamics at Avoided Level Crossings in LiY0.998Ho0.002F4, M. J. Graf, J. Lago, A. Lascialfari, A. Amato, C. Baines, S. R.Giblin, J. S. Lord, A. M. Tkachuk, and B. Barbara, Phys. Rev. Lett. 99, 267203 (2007).
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