Separation of Topographic Features from Magnetic Images Using Capacitive Coupling Effect: Computational Approach
Separation of topographic features from magnetic images has been an issue in magnetic force microscopy (MFM) since its development two decades ago. Recently, we developed a separation method using the capacitive coupling effect between the cantilever and the sample surface by using electrostatic modulation. The frequent pickups of the topographic features are interpreted as transitions of the tip between bi-stable states of the tip-sample assembly in the noncontact and tapping regions. The MFM with electrostatic force modulation demonstrated the separation of the topographic features from the magnetic images by removing the tapping state from the bi-stable states through the introduction of a capacitive coupling. As an approach to understand this separation mechanism, we calculated the amplitude and deflection of the cantilever as a function of frequency and distance. The Newtonian motion of the MFM probe cantilever was numerically solved under the static magnetic force of the sample, the oscillatory electrostatic force in the noncontact regime, and the Hertzian elastic force in the contact regime. The calculated amplitude-frequency, amplitude-distance, and force-distance curves were consistent with those reported in the literature, confirming that the capacitive coupling is the primary origin of the separation mechanism in the MFM using the electrostatic force modulation.