Hyperfine Interactions and Spin Transport in Ferromagnet-Semiconductor Heterostructures (2009)
Chan, M. K., Hu, Q. O., Zhang, J., Kondo, T., Palmstrøm, C. J., Crowell, P. A.
Measurements and modeling of electron spin transport and dynamics are used to characterize hyperfine interactions in Fe/GaAs devices with $n$-GaAs channels. Ga and As nuclei are polarized by...
Bias-controlled sensitivity of ferromagnet/semiconductor electrical spin detectors (2008)
Crooker, S. A., Garlid, E., Chantis, A. N., Smith, D. L., Reddy, K. S. M., Hu, Q., ...
Using Fe/GaAs Schottky tunnel barriers as electrical spin detectors, we show that both the magnitude and sign of their spin-detection sensitivities are widely tunable with voltage bias applied across...
Electrical Detection of Spin Transport in Lateral Ferromagnet-Semiconductor Devices (2006)
Lou, X., Adelmann, C., Crooker, S. A., Garlid, E. S., Zhang, J., Reddy, S. M., ...
A longstanding goal of research in semiconductor spintronics is the ability to inject, modulate, and detect electron spin in a single device. A simple prototype consists of a lateral semiconductor...
Optical and electrical spin injection and spin transport in hybrid Fe/GaAs devices (2006)
Crooker, S. A., Furis, M., Lou, X., Smith, D. L., Adelmann, C., Palmstrom, C. J., ...
We discuss methods for imaging the nonequilibrium spin polarization of electrons in Fe/GaAs spin transport devices. Both optically- and electrically-injected spin distributions are studied by...
Dynamics of Pinned Magnetic Vortices (2006)
Compton, R. L., Crowell, P. A.
We observe the dynamics of a single magnetic vortex in the presence of a random array of pinning sites. At low excitation amplitudes, the vortex core gyrates about its equilibrium position with a...
Adelmann, C., Lou, X., Hilton, J. L., Schultz, B. D., McKernan, S., ...
Electrical spin injection from ferromagnetic $\delta$-MnGa into an (Al,Ga)As p-i-n light emitting diode (LED) is demonstrated. The $\delta$-MnGa layers show strong perpendicular magnetocrystalline...
Electrical Detection of Spin Accumulation at a Ferromagnet-Semiconductor Interface (2006)
Lou, X., Adelmann, C., Furis, M., Crooker, S. A., Palmstrom, C. J., Crowell, P. A.
We show that the accumulation of spin-polarized electrons at a forward-biased Schottky tunnel barrier between Fe and n-GaAs can be detected electrically. The spin accumulation leads to an additional...
Interactions of spin waves with a magnetic vortex (2005)
We have investigated azimuthal spin-wave modes in magnetic vortex structures using time-resolved Kerr microscopy. Spatially resolved phase and amplitude spectra of ferromagnetic disks with diameters...
Strand, J., Lou, X., Adelmann, C., Schultz, B. D., Isakovic, A. F., Palmstrom, C. J., ...
We have studied hyperfine interactions between spin-polarized electrons and lattice nuclei in Al_0.1Ga_0.9As/GaAs quantum well (QW) heterostructures. The spin-polarized electrons are electrically...
Spin injection from the Heusler alloy Co_2MnGe into Al_0.1Ga_0.9As/GaAs heterostructures (2004)
Dong, X. Y., Adelmann, C., Xie, J. Q., Palmstrom, C. J., Lou, X., Strand, J., ...
Electrical spin injection from the Heusler alloy Co_2MnGe into a p-i-n Al_0.1Ga_0.9As/GaAs light emitting diode is demonstrated. A maximum steady-state spin polarization of approximately 13% at 2 K...
Spin Injection and Relaxation in Ferromagnet-Semiconductor Heterostructures (2004)
Adelmann, C., Lou, X., Strand, J., Palmstrom, C. J., Crowell, P. A.
We present a complete description of spin injection and detection in Fe/Al_xGa_{1-x}As/GaAs heterostructures for temperatures from 2 to 295 K. Measurements of the steady-state spin polarization in...
Nuclear Magnetic Resonance in a Ferromagnet-Semiconductor Heterostructure (2003)
Strand, J., Schultz, B. D., Isakovic, A. F., Lou, X., Palmstrom, C. J., Crowell, P. A.
We report the observation of nuclear magnetic resonance (NMR) in a ferromagnet-semiconductor heterostructure in the presence of a spin-polarized current. Spin-polarized electrons injected from a...
Strand, J., Schultz, B. D., Isakovic, A. F., Palmstrom, C. J., Crowell, P. A.
Electrical spin injection from Fe into Al$_x$Ga$_{1-x}$As quantum well heterostructures is demonstrated in small (< 500 Oe) in-plane magnetic fields. The measurement is sensitive only to the...
Imaging of Spin Dynamics in Closure Domain and Vortex Structures (2002)
Park, J. P., Eames, P., Engebretson, D. M., Berezovsky, J., Crowell, P. A.
Time-resolved Kerr microscopy is used to study the excitations of individual micron- scale ferromagnetic thin film elements in their remnant state. Thin (18 nm) square elements with edge dimensions...
Spatially Resolved Dynamics of Localized Spin-Wave Modes in Ferromagnetic Wires (2002)
Park, J. P., Eames, P., Engebretson, D. M., Berezovsky, J., Crowell, P. A.
We have observed localized spin-wave modes in individual thin-film ferromagnetic wires using time-resolved Kerr microscopy as a micron-scale spectroscopic probe. The localization is due to the...
Isakovic, A. F., Carr, D. M., Strand, J., Schultz, B. D., Palmstrom, C. J., Crowell, P. A.
Epitaxial ferromagnetic metal - semiconductor heterostructures are investigated using polarization-dependent electroabsorption measurements on GaAs p-type and n-type Schottky diodes with embedded...
Time-resolved ferromagnetic resonance in epitaxial Fe1-xCox films (2001)
Engebretson, D. M., Zellinger, S., Chen, L. C., Palmstrom, C. J., Crowell, P. A.
Magnetodynamics in epitaxial Fe1-xCox films on GaAs (100) are studied using time-resolved ferromagnetic resonance, in which the free precession of the magnetization after an impulsive excitation is...
Onset of Superfluidity in 4He Films Adsorbed on Disordered Substrates (1996)
Crowell, P. A., Van Keuls, F. W., Reppy, J. D.
We have studied 4He films adsorbed in two porous glasses, aerogel and Vycor, using high precision torsional oscillator and DC calorimetry techniques. Our investigation focused on the onset of...
The Bose--Hubbard Model and Superfluid Staircases in $^{4}$He Films (1993)
Zimanyi, G. T., Crowell, P. A., Scalettar, R. T., Batrouni, G. G.
The recent experimental observation of step-like structure in the superfluid density of $^{4}$He films on graphite is interpreted in terms of passage close to Mott insulating lobes in the...