# Parametric pumping and kinetics of magnons in dipolar ferromagnets

Source: [Parametric pumping and kinetics of magnons in dipolar ferromagnets](<https://www.sota2.com/research/paper/68fa29441e209131ce832140>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2025-10-28T13:53:01.054Z

Authors: Thomas Kloss, Andreas Kreisel, Peter Kopietz

Published: 2009-12-16T21:01:03.000Z

## Abstract

The time evolution of magnons subject to a time-dependent microwave field is usually described within the so-called "S-theory", where kinetic equations for the distribution function are obtained within the time-dependent Hartree-Fock approximation. To explain the recent observation of "Bose-Einstein condensation of magnons" in an external microwave field \[Demokritov et al., Nature 443, 430 (2006)\], we extend the "S-theory" to include the Gross-Pitaevskii equation for the time-dependent expectation values of the magnon creation and annihilation operators. We explicitly solve the resulting coupled equations within a simple approximation where only a single condensed mode is retained. We also re-examine the usual derivation of an effective boson model from a realistic spin model for yttrium-iron garnet films and argue that in the parallel pumping geometry (where both the static and the time-dependent magnetic field are parallel to the macroscopic magnetization) the time-dependent Zeemann energy cannot give rise to magnon condensation.

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## Original sources and implementation

[Original paper](<https://arxiv.org/abs/0912.3254>)

[PDF](<https://arxiv.org/pdf/0912.3254.pdf>)