Quantitative Evaluation of Current through Magnetic Field Observation by Magnetic Force Microscopy

Magnetic field around fine current paths has been investigated by magnetic force microscopy (MFM) for a purpose of current evaluation with high spatial resolution. In this paper, the MFM observation of magnetic field around an artificial current network to discuss ability in quantitative evaluation of current is discussed. In this method, the alternating current pass through the network, whose frequency is tuned to be coincident with the torsional resonant frequency of an MFM cantilever (typically, 300 kHz), and torsional displacement of the cantilever is extracted by a lock-in technique as a magnetic force signal, while vertical displacement due to mechanical vibration is used for height control of the tip. This allows us to observe a magnetic force image and a topographic image, simultaneously.