Surface Roughness Effects on Magnetization Reversal of Magnetic Ring Elements
The effect of surface roughness on magnetoresistance of permalloy ring structure is investigated. Microstructured permalloy rings with surface roughness varying from 4.2 to 21 nm were fabricated using electron beam lithography and a chemical etching process. It is found experimentally that the first and second nucleation fields decrease obviously with the surface roughness increasing, and the field range for the flux-closure state is not associated with surface roughness. The results indicate that surface roughness in permalloy ring structure is an important factor that influences the magnetic behaviors of the ring. This result can provide important information for future designs of ring-shaped magnetic devices.
Control of magnetization states in microstructured permalloy rings
Magnetization processes of microstructured NiFe rings are studied by the fringe-field-induced local Hall effect and numerical model calculations. The changes in reversible and irreversible magnetization of single rings are detected with very high resolution. We observe that the type of magnetic transition depends on the ratio between the inner and outer ring diameter. For narrow rings, sharp transitions from so-called “onion” to the “vortex” state are observed. In rings with smaller inner diameter, the transitions are more complex. The creation of local vortices and their spatial movement by applying an external magnetic field are detected.
Photoreflectance characterization of vanadium-doped GaAs layers grown by metalorganic vapor phase epitaxy
Abstract We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy. The conductivity of the samples is checked by the Hall effect measurements, and it is n type with electrons concentration ranging from 2×10 13 to 2×10 17  cm −3 . We used the photoreflectance technique (PR) to study the effect of vanadium doping on the optical properties of GaAs. Our experimental results show that the built-in electric field F and the broadening parameter Γ 0 increase with V-doping concentration. Furthermore, the temperature dependence of the built-in electric field and the broadening parameter of GaAs:V samples have been investigated by PR. It has been observed that these parameters increase with increasing temperature. The decrease of the built-in electric field with decreasing temperature is due to the photovoltage effect.We characterized the vanadium-doped GaAs (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy.