We have attached single ferromagnetic particles of 8μm diameter to the tips of microfabricated atomic force microscope cantilevers. These cantilevers were magnetized to fix the magnetization direction of the ferromagnetic particles and scanned in a controlled manner over a spin valve structure of dimension 12×8μm2. Two dimensional image scans representing the change in resistance of the spin valve due to a scanning bead were obtained. The results are explained using a simple model where the scanning bead is treated as a pure dipole.
In this work, we present a combinatory approach where optical tweezers were used to trap and position a single superparamagnetic particle over a spin valve sensor, with the particle then detected by the sensor. This approach is demonstrated using superparamagnetic particles of 2μm together with a spin valve sensor with dimensions of 2×4μm2, whereby a single magnetic particle was positioned over the sensor and a corresponding drop in the voltage across the sensor was detected. The results are explained using a simple model where the particle is treated as a pure magnetic dipole.
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