Magnon Generation Research Articles

On the question of magnon generation in antiferromagnets under conditions of intense optical pumping

It is established that quasiparticle generation does not occur in a system of excitons parametrically excited by means of optical pumping at intensities of up to 100 mW/cm2. Causes of the disagreement between the experimental and theoretical values for the threshold intensity are discussed.

Generation of short wavelength magnons in ferromagnetic semiconductors

We study the conditions of generation of magnons in ferromagnetic semiconductors excited by both an electromagnetic and a d.c. electric field. We conclude that the rate of generation of magnons may become greater than the rate of relaxation and the magnon system may reach instability.

Coherent generation of magnons by optical techniques

A new technique for the coherent excitation of magnons is proposed which is based on the magnetic Raman nonlinearity. The excitation is obtained by mixing two laser beams with different frequencies (ω1,ω2) under phase-match conditions [when (ω1−ω2) is equal to the frequency of one magnon mode and (k1−k2) is equal to the magnon wavevector]. The method allows selective excitation in frequency and wavevector and may by useful for magnon relaxation measurements. The proposed process is analyzed by quantum statistical methods. The number of excited magnons and the coherence properties of the generated states are investigated by using the representation of coherent magnon states. The results show that it is possible to excite a magnon population of the same order of magnitude as in nonlinear magnetic resonance experiments by using lasers with powers of hundreds of watts. The possibility of experimental observation is analyzed in detail for both ferromagnetic and antiferromagnetic materials.

High frequency magnon generation by nonequilibrium electrons and the instability of the magnon system

The high frequency magnon generation by nonequilibrium electrons polarized opposite the magnetization vector is investigated. At some conditions the avalanche-type generation of magnons with wavevectors along the magnetization takes place and the magnon system becomes unstable.

On the possibility of induced oscillation of magnons

The generation of magnons in ferrodielectrics with impurities is theoretically treated with the weakly bonded impurity spins taken as active centers. The optical pumping is assumed and the threshold values of pumping are found, as well as the minimum impurity concentration required for the oscillation. Estimations show that the oscillation conditions can be easily realized.