Resistivity measurement for non-magnetic materials using high-order resonance mode of MFM-cantilever oscillation

Abstract A method to measure the electrical resistivity of materials using magnetic-force microscopy (MFM) is discussed, where MFM detects the magnetic field caused by the tip-oscillation-induced eddy current. A high cantilever oscillation frequency is preferable to achieve high sensitivity because it induces large eddy currents in the material. Higher-order resonance modes of the cantilever oscillation lead to higher frequency. To discuss such high-order-mode oscillation, a differential equation governing MFM cantilever oscillation in the high-order resonance mode is formulated, and an analytical solution of the phase difference is obtained. The result shows that the phase difference decreases at higher modes because the effective spring constant increases faster than the force from the eddy current.