Dual-cantilever magnetometer for study of magnetic interactions between patterned permalloy microstructures

Highlights: • Design and fabrication of a dual-cantilever magnetometer. • The study of magnetic interactions between two ferromagnetic microstructures. • Control of magnetic coupling between the cantilevers by an external field. • Phase shift detection of changes in magnetic states of the microstructures. • Results confirmed by MFM measurements and micromagnetic simulations. - Abstract: We have designed and implemented a dual-cantilever magnetometer, in which the coupling magnetic forces between the two cantilevers can be switched on/off by an external magnetic field. The coupling is realized by a pair of ferromagnetic ellipses, located on the cantilevers. One of the ellipses is "narrow" – it bears only a single domain magnetic state independently of the applied external field. The other one is "wide", and can be either in single- or closure-domain states depending on the applied field. In such configuration, the interacting force between the cantilevers can be attractive (both ellipses are in single domain state conforming to the external field), repulsive (both are in single domain states, but the narrow ellipse is in a meta-stable state, with magnetization opposite to the field) or switched off (when the closure domain state appears in the wide ellipse). We found that the coupling between the ellipses directly corresponds to the phase shift of the vibrating cantilevers. In this manner, the cantilever phase detection can be used to read out the magnetic state of the ellipses, which depends on the applied magnetic field. Moreover, we study how the magnetic state of the wide ellipse influences the flipping field of the narrow ellipse. Our observations are supported by micromagnetic simulations and by additional magnetic force microscopy experiments. We also discuss sensitivity and potential application of the magnetometer in future experiments.