A high performance magnetic force microscope

We have constructed a high performance magnetic force microscope optimized for operation in the force gradient detection mode. The instrument incorporates a novel differential heterodyne interferometer that has a high immunity to microphonics and interference. The detection limit of the interferometer is limited by the intrinsic thermal noise of the cantilever sensor. Positioning and scanning of the sample is undertaken by a monolithic flexure stage driven by piezoelectric actuators. The stage incorporates capacitance sensors which are used to linearize the motion of the stage via a closed loop control system. The linearity achieved is better than 1% (full scale) with a positioning stability of 1 nm (rms). Recorded bit patterns in longitudinal media and domains in an AC-demagnetized Co/Pt multilayer have been studied.