  Cavity Magnonics is an emerging field that studies the strong coupling
between cavity photons and collective spin excitations such as magnons. This
rapidly developing field connects some of the most exciting branches of modern
physics, such as quantum information and quantum optics, with one of the oldest
science on the earth, the magnetism. The past few years have seen a steady
stream of exciting experiments that demonstrate novel magnon-based transducers
and memories. Most of such cavity magnonic devices rely on coherent coupling
that stems from direct dipole-dipole interaction. Recently, a distinct
dissipative magnon-photon coupling was discovered. In contrast to coherent
coupling that leads to level repulsion between hybridized modes, dissipative
coupling results in level attraction. It opens an avenue for engineering and
harnessing losses in hybrid systems. This article gives a brief review of this
new frontier. Experimental observations of level attraction are reviewed.
Different microscopic mechanisms are compared. Based on such experimental and
theoretical reviews, we present an outlook for developing open cavity systems
by engineering and harnessing dissipative couplings.
