  Remote sensing of magnetic nanoparticles has exciting applications for
magnetic nanoparticle hyperthermia and molecular detection. We introduce,
simulate, and experimentally demonstrate an innovation---a sensing coil that is
geometrically decoupled from the excitation field---for magnetic nanoparticle
spectroscopy that increases the flexibility and capabilities of remote
detection. The decoupling enhances the sensitivity absolutely; to small amounts
of nanoparticles, and relatively; to small changes in the nanoparticle
dynamics. We adapt a previous spectroscopic method that measures the relaxation
time of nanoparticles and demonstrate a new measurement of nanoparticle
temperature that could potentially be used concurrently during hyperthermia.
