Magnetotransport and magnetocrystalline anisotropy in Ga1-xMnxAs epilayers

We present an analysis of the magnetic anisotropy in epitaxial Ga1-xMnxAs thin films through electrical transport measurements on multiterminal microdevices. The film magnetization is manipulated in 3D space by a three-axis vector magnet. Anomalous switching patterns are observed in both longitudinal and transverse resistance data. In transverse geometry in particular we observe strong interplay between the anomalous Hall effect and the giant planar Hall effect. This allows direct electrical characterization of magnetic transitions in the 3D space. These transitions reflect a competition between cubic magnetic anisotropy and an effective out-of-plane uniaxial anisotropy, with a reversal mechanism that is distinct from the in-plane magnetization. The uniaxial anisotropy field is directly calculated with high precision and compared with theoretical predictions

Magnetoelectronic Phenomena at a Ferromagnet-Semiconductor Interface

A Comment on the Letter by P. R. Hammar et al., Phys. Rev. Lett. 83, 203 (1999)

Slow Atomic Motion in Zr-Ti-Cu-Ni-Be Metallic Glasses Studied by NMR

Nuclear magnetic resonance is used for the first time to detect slow atomic motion in metallic glasses, specifically, Be motion in Zr-Ti-Cu-Ni-Be bulk metallic glasses. The observations are not consistent with the vacancy-assisted and interstitial diffusion mechanisms and favor the spread-out free volume fluctuation mechanism for Be diffusion. Comparison with the results of Be diffusion measured by elastic backscattering the NMR results also indicates that the energy barriers for short- and long-range Be motion are the same

Two-dimensional electron-gas actuation and transduction for GaAs nanoelectromechanical systems

We have fabricated doubly clamped beams from GaAs/AlGaAs quantum-well heterostructures containing a high-mobility two-dimensional electron gas (2DEG). Applying an rf drive to in-plane side gates excites the beam's mechanical resonance through a dipole–dipole mechanism. Sensitive high-frequency displacement transduction is achieved by measuring the ac emf developed across the 2DEG in the presence of a constant dc sense current. The high mobility of the incorporated 2DEG provides low-noise, low-power, and high-gain electromechanical displacement sensing through combined piezoelectric and piezoresistive mechanisms