The magnon BEC observation by switch off method

Abstract

The Bose-Einstein condensation (BEC) corresponds to the formation of a collective quantum state in which macroscopic number of particles is governed by a single wave function. The magnon BEC forms by excited non-equilibrium magnons and manifests itself by coherent precession of magnetization even in an inhomogeneous magnetic field. The magnon BEC is very similar to an atomic BEC, but the potential of the interaction between magnons may variate very significantly. The superfluid phases of 3He are the best antiferromagnetic system for investigations of magnon BEC and spin superfluidity. The 6 different states of magon BEC were observed in 3He. Recently magnon BEC was observed in antiferromagnets with Suhl-Nakamura interaction and ferrites. Here we review for the first time the switch offNMR method, when magnon BEC forms during a long radiofrequency pulse. The new experimental results are discussed.

Magnonics and Supermagnonics

“…The observation was done on quasinuclear branch of precession, which characterized by Gilbert damping factor of about 10 −5 and the repulsive interaction between magnons. The new techniques of magnon BEC formation was developed:the non-resonance excitation of magnon BEC [57] and the switch off RF field method [59]. The magnon BEC was observed even in very inhomogeneous conditions [58].…”