X-band EPR with bilateral twins of composite magnets

We report a field-variable magnet system using four pieces of permanent magnets, adding another design to the lineup of compact EPR systems. Two of them join magnetically by themselves and form composite magnets. With its duplicate made up of the rest two, the twins of the composite magnets face with each other, creating at the middle point a sweet spot of the magnetic field that can be varied by adjusting the twins' separation under precise and reproducible motor control over a wide range up to 450 mT using 20×20×20mm samarium cobalt magnets. The magnet system is built up without sticky adhesives and can easily be disassembled and reassembled. The repelling force acting on the twins leads to safe operation without concern about collision accidents. With an in-house probe employing a dielectric resonator, we demonstrate EPR measurements in the X-band using the developed magnet system, also discussing the effect of the inhomogeneity of the magnetic field.