Magnetic particle imaging with a cantilever torque magnetometer

We have demonstrated magnetic particle imaging$^{1 }$with a cantilever torque magnetometer. Imaging is based on measuring the harmonic content of the magnetic moment of a particle driven to saturation by an applied ac magnetic field while adjusting the zero point of the field gradient with a slowly sweeping dc magnetic field. Large field gradients ($>$ 100 T/m) necessary for high resolution imaging can be generated by opposing electromagnets with ferrite cores and thus there is the potential for submicrometer image resolution. Results on an array of 50 $\mu $m Permalloy dots patterned on microcantilevers will be reported. $^{1}$B. Gleich and J. Weizenecker, Nature 435, 1214 (2005).