RESUMEN
We present a systematic change of the magnetic domain structure with temperature in epitaxial ferromagnetic MnAs film on GaAs (001), observed in a wide temperature range of 15-45 degrees C by magnetic force microscopy. Interestingly, it is found that, as temperature increases, the domain structure within the ferromagnetic alpha-MnAs stripes shows a mixture of head-on and simple domains at 15 degrees C and then, takes a complete transition to simple ones above 15 degrees C. This change could be understood by change in the demagnetizing factor of the cross-section of the ferromagnetic stripes with temperature.
RESUMEN
A huge positive magnetoresistance effect, about 4 orders of magnitude at room temperature, was discovered in metal-semiconductor hybrid nanostructures. The hybrid material consisting of metallic nanostructures that are fabricated on a GaAs substrate by ultra-high vacuum deposition method exhibits magnetic field-sensitive current-voltage characteristics. When a constant voltage above the threshold value, is applied to the film, a very steep change in the current, which we term magnetoresistive switch, is driven by the huge magnetoresistance effect under a relatively low magnetic field at room temperature. The magnetoresistance effect is very sensitive to the nanoscale morphology of the hybrid film; in other words, one can control the magnetoresistance function at will by modifying the nanostructure of this material. The origin of the magnetoresistive switch effect and its possible application as a magnetic field sensor is discussed.