Stability of Bose Einstein condensates of hot magnons in Yttrium Iron Garnett

Sasha Burin                                                                         
Tulane University                                                                   
                                                                                    
We investigate the stability of the recently discovered room temperature
Bose-Einstein condensate (BEC) of magnons in Ytrrium Iron Garnet (YIG)
films. We show that magnon-magnon interactions depend strongly on the external
field orientation, and that the BEC in current experiments is actually
metastable - it only survives because of finite size effects, and because the
BEC density is very low. On the other hand a strong field applied
perpendicular to the sample plane leads to a repulsive magnon-magnon
interaction; we predict that a high-density magnon BEC can then be formed in
this perpendicular field geometry.