Title: Observation of spin superfluidity: YIG magnetic films and beyond,
Abstract: From topology of the order parameter of the magnon condensate observed in
yttrium-iron-garnet (YIG) magnetic films one must not expect energetic barriers
making spin supercurrents metastable. But we show that some barriers of
dynamical origin are possible nevertheless until the gradient of the phase
(angle of spin precession) does not exceed the critical value (analog of the
Landau critical velocity in superfluids). On the other hand, recently published
claims of experimental detection of spin superfluidity in YIG films and
antiferromagnets are not justified, and spin superfluidity in magnetically
ordered solids has not yet been experimentally confirmed.