A probe for detecting magnetostatic surface resonant spheres

We propose a novel probe for detecting magnetostatic surface resonant spheres. The probe is composed of a two-loop resonator in which the inner loop is loaded with a capacitor whose value can be adjusted to achieve probe resonance at desired frequency. This probe produces substantial variation in its reflection coefficient in presence of a magnetostatic resonant sphere with negative real permeability, whereas non-resonant spheres do not yield any significant effect. The mechanism behind this is explained and can be generalized to detect magnetostatic resonant spheres in low microwave frequencies. Probe design is presented along with full-wave numerical simulations.