Theory of magnetic dissipation imaging

A model is presented for magnetic dissipation imaging and magnetic force gradient imaging obtained with a vibrating ferromagnetic tip and a ferromagnetic thin film sample. Results of calculations are compared to recent experiments and show good agreement using known bulk values for the magnetic parameters of tip and sample. We suggest that oscillations of domain wall width result in magnetoelastic emission of phonons. These phonons carry energy from the tip, leading to image contrast at domain walls. We also discuss the energy dissipation resulting from eddy current losses in the tip and sample.