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Hi
Can someone please tell me why phase contrast MFM, leads to a change in phase, rather than amplitude. It seems like an obvious question but I can`t seem to find an answer in the literature.
S
The magnetic force gradient leads to a resonant frequency shift of the cantilever. The phase shift related to the resonance follows this shift.
Since we are driving at a constant frequency, a change in both phase and amplitude will be observed in the lock-in outputs, but phase is more popular since the contrast can be higher without big changes in signal level. I like the book by Sarid for this sort of theory question. It is old, but covers many interesting SPM cases.
--Bede