Detection of Magnetic Field Gradient around a Current Path by Magnetic Force Microscopy

摘要

For a purpose of measuring local transport properties in fine structures, a novel current detection method through magnetic force microscopy was proposed and demonstrated. Around an 8 mum wide GaAs/AlGaAs mesa stripe, the magnetic fields induced by AC currents were observed by MFM simultaneously with topographies. Since a direction of the magnetic field gradients is perpendicular to the mesa stripe, the obtained magnetic field images strongly depended on the measuring configurations, in which the cantilever beam and the mesa stripe were in parallel or in perpendicular. As we expected, the amplitude was under the noise level in the perpendicular configurations, while we clearly observed the enhancement of amplitude and the phase inversion at the both sides of the mesa stripe in the parallel configuration. These results agreed very well with the numerical simulation which showed the existence of the large magnetic field gradients at the both sides of the mesa stripe. Linear relationship between the peak amplitude values and the AC current was also confirmed.