Figure 2: Basic driving protocol for magnetic susceptibility force microscopy (χFM).
From: Ultrasensitive mechanical detection of magnetic moment using a commercial disk drive write head
A sinusoidal current with frequency fc/2 is applied to the coil of the write element, generating an oscillating pole magnetic field B and gradient ∇|B|. The oscillating field in turn induces an oscillating sample magnetization M=χ B/μ0. The sample with volume V experiences a magnetic force F=V∇(M·B) that drives the mechanical resonance fc of an ultrasensitive cantilever force transducer. The amplitude of the resulting cantilever oscillation x is proportional to the force. Tc=1/fc is one cantilever oscillation period.
