  Tailoring of electromagnetic spontaneous emission predicted by E. M. Purcell
more than 50 years ago has undoubtedly proven to be one of the most important
effects in the rich areas of quantum optics and nanophotonics. Although during
the past decades the research in this field has been focused on electric dipole
emission, the recent progress in nanofabrication and study of magnetic quantum
emitters, such as rare-earth ions, has stimulated the investigation of the
magnetic side of spontaneous emission. Here, we review the state-of-the-art
advances in the field of spontaneous emission enhancement of magnetic dipole
quantum emitters with the use of various nanophotonics systems. We provide the
general theory describing the Purcell effect of magnetic emitters, overview
realizations of specific nanophotonics structures allowing for the enhanced
magnetic dipole spontaneous emission, and give an outlook on the challenges in
this field, which remain open to future research.
