On the nature of the amplified spin echo in garnets

YIG magnonics

“…It has also been discovered that slow BVMSW at the bottom of magnon spectrum, which can be effectively excited in conditions of nonuniform magnetic bias field near the edges of bulk samples, and slow MSSW existing in uniformly magnetized YIG films just above the frequency of ferromagnetic resonance [150] can participate in the echo process. Signal restoration can be achieved by perpendicular pumping where -by analogy with the wavefront reversal process described in section 4.3 -the perpendicular pump generates a set of phase conjugate oscillations [146,147,148,149,150]. Two features distinguish such an echo from, for example nuclear or paramagnetic spin echoes.…”

“…Echo phenomena have been studied in detail in many physical systems [141]. Observation of a spin-wave echo (or magnetostatic mode echo) brought about via two external pumping pulses of the same frequency was first reported in 1965 [142] and over the last forty years a high level of understanding of the detailed physics of the mechanism has been attained (see for example [143][144][145][146] and references therein). Many theoretical models have been developed to explain the spin-wave echo phenomenon [144][145][146].…”

“…Observation of a spin-wave echo (or magnetostatic mode echo) brought about via two external pumping pulses of the same frequency was first reported in 1965 [142] and over the last forty years a high level of understanding of the detailed physics of the mechanism has been attained (see for example [143][144][145][146] and references therein). Many theoretical models have been developed to explain the spin-wave echo phenomenon [144][145][146]. In order for phase relaxation to take place, these require the presence of many spatially localized spin-wave modes with different frequencies.…”

“…Signal restoration can be achieved by perpendicular pumping where-by analogy with the wavefront reversal process described in section 4.3-the perpendicular pump generates a set of phase conjugate oscillations [143][144][145][146][147]. Two features distinguish such an echo from, for example, nuclear or paramagnetic spin echoes.…”

Magnon Spintronics

“…A first can be formed using perpendicular parametric pumping through a mechanism similar to that which underpins the wavefront reversal process described in "Wavefront Reversal via Parallel Parametric Pumping" [130][131][132]. A second operates through parallel pumping of secondary dipole-exchange waves generated via two-magnon scatter of an initial excitation belonging to the dipolar part of the spectrum [133,134].…”