Magnetic particle imaging with a cantilever detector

We present a novel imaging method for measuring the position and magnetic moment of single micrometer scale particles. Our technique is based on magnetic force microscopy (MFM) with a magnetically hard magnetic tip in a uniform opposing field. By translating the MFM probe tip laterally and vertically, the local magnetic field at a particle can be precisely controlled. Our technique is similar to magnetic particle imaging, where the harmonic response of a particle to an AC field is measured; the difference is that here, the response is measured with a cantilever instead of a detector coil. We are able to precisely determine individual particle positions to within +/−0.022 μm in a composite sample. In addition, by fitting the force derivative images taken at different distances above the sample and at different applied magnetic fields, we can determine the m-H characteristics of individual particles.