Superferromagnetic Disk Particles for Magnetic Particle Imaging

Magnetic particle imaging (MPI) offers rapid, highly sensitive tracer-based imaging without ionizing radiation, but its clinical translation remains challenged by the limited performance of existing superparamagnetic (SP) tracers. In this work, precisely engineered disk-shaped nanoparticles fabricated from superferromagnetic (SF) discontinuous metal-insulator multilayers (DMIMs) consisting of SP nanoscale metal islands embedded in a nonmagnetic oxidic matrix are introduced. By leveraging inter-island exchange interactions, robust SF behavior is achieved in extended DMIMs, exhibiting exceptionally high susceptibilities and a sharp magnetization switching at fields below 1 mT. When evaluated in MPI experiments, magnetic disk particles (MDP) with a diameter of 1800 nm patterned from the SF DMIMs demonstrate up to a 1.6-fold improvement in spatial resolution and a 2.4-fold increase in sensitivity compared to Perimag tracers, the current gold standard in MPI. System matrix measurements and hybrid MPI reconstructions further highlight the superior imaging characteristics of MDP tracers in complex, clinically relevant geometries. These findings establish SF DMIM disks as a promising next-generation tracer platform for MPI, with the potential to simplify scanner designs and to pave the way for a clinical translation of MPI.