Magnetic Susceptibility Measurement of Single Micro-Particle by Magnetophoretic Velocimetry

It has been highly required to analyze environmental or biological micro-particles noninvasively and nondestructively, since they have each characteristic function in the surface and inside the individual particle. Magnetophoretic velocimetry is a novel migration method, that allows us to measure the magnetic susceptibility of a single micro-particle, and can satisfy this requirement. A high magnetic field gradient generated by a superconducting magnet and a pair of pole pieces were used, in order to enhance the sensitivity of magnetophoretic velocimetry. The apparatus for observation of magnetophoresis in the gradient was constructed. The magnetic susceptibility of a micro-droplet adsorbed by a paramagnetic Dy(III) complex was measured, and reciprocally depended on the radius of the droplet. Dy(III) on the interface could be determined from this dependency. Furthermore, a photo-induced spin transition of single micro-crystal of Co-Fe Prussian blue analogues could be observed from an abrupt increase of magnetophoretic velocity after pulse laser irradiation.