We demonstrated the measurement of the high frequency(HF)magnetic field of a write head with the phase detection magnetic force microscope. An amplitude-modulated current was applied to the head coil to detect the force gradient induced by the HF magnetic field. Spatial resolution of this method(AC-phase detection) was higher than that of the deflection detection method previously proposed(AC-deflection detection). By the phase detection method, dynamic HF magnetic fields and the magnetic field leakage were clearly imaged. The frequency dependence of the write head dynamics up to 350MHz was also investigated. Not only magnitude but also contrast(distribution)of the HF magnetic field that was caused by the eddy current was observed.
