Explosive dynamics and localization of wave triads in a coupled magnetoelastic system

Abstract

The dynamics of three-wave parametric coupling is considered on an example of nonequilibrium magnetostrictive medium under electromagnetic pumping. Subthreshold and supercritical mode of three-wave excitation are described analytically and simulated numerically for a triad of magnetoelastic waves. Theoretical analysis of the supercritical mode shows that space-time development of three-wave excitation in such a nonequilibrium system has the character of explosive instability and localization of "positive energy" waves.

Explosive instability of quasi-phonon triads in antiferromagnet under frequency modulated electromagnetic field

“…Contrary to previous work [4,5] where the first-order equations for slowly varying envelopes were used, the complete nonlinear model of EPAF low frequency dynamics described in Ref. [1] is used here in order to take into account high expected amplitudes of magnetic oscillations.…”

“…If the higher-order nonlinearity is neglected, the generation of quasi-phonon triads would be accompanied by explosive instability [4,5]. The threshold condition for this instability is [4] G ¼…”

“…The giant acoustic nonlinearity of EPAFs favours multi-boson coupling of quasi-phonons. Recently three-boson coupled excitations were predicted and observed in magnetoelastic system of EPAF a-Fe 2 O 3 under homogeneous RF electromagnetic pumping [4,5]. In comparison with three-boson equilibrium bound states (see Ref.…”

“…On the other hand, in contrast with parametric generation of quasiphonon pairs [1], the threshold of three-boson instability depends not only on intensity of pumping field but also on initial number of bosons. The pulse dynamics similar to explosive one [5] was detected in the model of two quasi-phonon parametric excitation with nonlinear feedback on the pumping source [8]. The manifestations of explosive supercritical dynamics in real EPAF crystals are smoothed over by higher-order nonlinear effects and first of all by nonlinear phase or frequency shift of magnetoelastic waves [1,9,10].…”

Three wave coupling and explosive instability of magneto-elastic excitations in FeBO3 single crystal

“…The coupling of three quasiphonons was observed recently in the ''easy plane'' phase of antiferromagnetic crystal a-Fe 2 O 3 under homogeneous RF electromagnetic pumping [2,3]. The theoretical analysis [2,4] has shown several specific dynamic features that differ the three wave coupling from well known parametric excitation of quasiphonon pairs. The first one is the dependence of instability threshold not only on amplitude of electromagnetic pumping but also on the number of initial quasi-phonons (i.e.…”