Magnon Supercurrent and the Phase Slippage in an Yttrium Iron Garnet Film

Exactly forty years ago, the spin superfluidity and Bose-Einstein condensation of magnons in superfluid antiferromagnetic 3He-B were discovered. In this work, the existence of spin superfluidity and phase slippage in an yttrium iron garnet film at room temperature is demonstrated using the optical Faraday effect. The s-patial distribution of the phase and amplitude of the spin precession under the conditions of magnon Bose-Einstein condensation are studied by varying the pump phase difference between two strip lines exciting magnons.