  A homogeneous negative permeability sphere can support magnetic localized
surface plasmons (MLSPs). Generally, negative permeability materials are
metamaterial (MM) structures exhibiting very deep subwavelength spatial scales,
whose effects may be detrimental in the near-field for those applications based
on effective medium approximations. We suggest to overcome this fundamental
limitation by demonstrating analytically that the electromagnetic spatial
distribution, associated to a MLSP resonance and excited by a near-field
source, can be accurately reproduced outside the sphere by substituting the
negative permeability sphere with a homogeneous high-index dielectric one with
the same radius. Considering that a large class of ferroelectric materials
shows ultra-high dielectric constant and low-losses at low frequency (up to
GHz), our spoof MLSPs theory could be a key tool for realizing high performance
subwavelength magnetic photonic devices in the radiofrequency and microwave
regions.
