Analysis of Magnetization Reversal Process of Nd–Fe–B Sintered Magnets by Magnetic Domain Observation Using Kerr Microscope
We used a Kerr microscope, image processing, and photo editing to clarify magnetization reversal and its propagation in a sintered Nd-Fe-B magnet. Magnetic domain change was observed when a dc field from +20 to 20 kOe was applied to a sintered Nd-Fe-B magnet. Simultaneous magnetization reversal in several grains along the easy axis direction and its propagation to neighboring grains occurred. This indicates that the nucleation field in a grain and magnetic interaction between grains are important controlling factors of the coercivity of sintered Nd-Fe-B magnets.
Domain behavior in sintered Nd‐Fe‐B magnets during field‐induced and thermal magnetization change
On sintered Nd‐Fe‐B permanent magnets, magnetic domain pattern changes in applied fields and at elevated temperatures were observed by the Kerr effect. Patterns on pole and side faces were recorded for different magnetization states in fields up to 17 kOe at 20 °C, and remanent patterns at temperatures up to TC. They are qualitatively interpreted. On pole faces, most grains are multidomain even at remanence. But the surface domains seen are not characteristic of the magnet interior. Side faces show mostly single‐domain grains at remanence. These images appear to reflect bulk behavior. Walls are strongly pinned at grain boundaries but move easily in the main magnetic phase, a behavior analogous to that of sintered SmCo5.
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.