Paul Crowell
Associate Professor
349 Tate, 624-4828/626-9371, email crowell @ physics.umn.eduhttp://www.physics.umn.edu/groups/fastspin/
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Research Areas: Spin dynamics and transport in ferromagnets and ferromagnet-semiconductor heterostructures.
Current Research
My research focuses on spin dynamics and transport in ferromagnets and ferromagnet-semiconductor heterostructures. In one of our projects, my group is exploring the excitation spectra of patterned ferromagnetic films using time-resolved Kerr microscopy. In these systems, the geometric confinement creates a non-uniform internal field profile that can lead to unique excitations, including localized spin waves. A low-temperature version of this experiment is probing the dynamics of ferromagnetic semiconductors. Our second principal project, in collaboration with Chris Palmstrom's group, addresses the difficult problem of injecting spins from a ferromagnetic metal into a semiconductor. Although semiconductors are in a sense an ideal environment for spin, an efficient means of introducing spin-polarized carriers electronically has not been developed. Among the interesting physics problems associated with this are understanding spin transport at interfaces between dissimilar materials, spin relaxation of hot electrons, and spin dynamics in large internal electric fields.
Selected Publications
X. Lou, C. Adelmann, S. A. Crooker, E. S. Garlid, J. Zhang, S. M. Reddy, S. D. Flexner, C. J. Palmstrøm, and P. A. Crowell, Electrical Detection of Spin Transport in Lateral Ferromagnet-Semiconductor Devices, Nature Physics 3, 197 (2007)
R. L. Compton and P. A. Crowell, Dynamics of a Pinned Magnetic Vortex, Phys. Rev. Lett. 97, 137202 (2006)
C. Adelmann, J. L. Hilton, B. D. Schultz, S. McKernan, C. J. Palmstrøm, X. Lou, H.-S. Chiang, and P. A. Crowell, Spin Injection from Perpendicular Magnetized Ferromagnetic δ-MnGa into (Al,Ga)As Heterostructures, Appl. Phys. Lett. 89, 112511 (2006)
X. Lou, C. Adelmann, M. Furis, S. A. Crooker, C. J. Palmstrøm, and P. A. Crowell, Electrical Detection of Spin Accumulation at a Ferromagnet-Semiconductor Interface, Phys. Rev. Lett. 96, 176603 (2006).
J. Strand, X. Lou, C. Adelmann, B. D. Schultz, A. F. Isakovic, C. J. Palmstrøm, and P. A. Crowell, Electron Spin Dynamics and Hyperfine Interactions in Fe/Al0.1Ga0.9As/GaAs Spin Injection Heterostructures, Phys. Rev. B 72, 155308 (2005).
J. P. Park and P. A. Crowell, Interactions of Spin Waves with a Magnetic Vortex, Phys. Rev. Lett. 95, 167201 (2005)
S. A. Crooker, M. Furis, X. Lou, C. Adelmann, D. L. Smith, C. J. Palmstrøm, and P. A. Crowell, Imaging spin injection and accumulation in lateral ferromagnet/semiconductor devices, Science 309, 2191(2005)
C. Adelmann, X. Lou, J. Strand, C. J. Palmstrøm, and P. A. Crowell, Spin Injection and Relaxation in Ferromagnet-Semiconductor Heterostructures, Phys. Rev. B 71 121301(R) (2005).
C. Bayer, J. P. Park, H. Wang, M. Yan, C. E. Campbell, and P. A. Crowell, Spin Waves in an Inhomogeneously Magnetized Stripe, Phys. Rev. B 69, 134401 (2004)
J. Strand, A. F. Isakovic, X. Lou, P. A. Crowell, B. D. Schultz, and C. J. Palmstrom, Nuclear Magnetic Resonance in a Ferromagnet-Semiconductor Heterostructure, Appl. Phys. Lett. 83, 3335 (2003)
Education