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arXiv · 0711.4285

Non-linear dynamics and two-dimensional solitons for spin $ S=1$ ferromagnets with biquadratic exchange

B. A. Ivanov·A. Yu. Galkin·R. S. Khymyn·A. Yu. Merkulov
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Abstract

We develop a consistent semiclassical theory of spin dynamics for an isotropic ferromagnet with a spin $ S=1$ taking into consideration both bilinear and biquadratic over spin operators exchange interaction. For such non-Heisenberg magnets, a peculiar class of spin oscillations and waves, for which the quantum spin expectation value $ {\rm {\bf m}}=<{\rm {\bf S}}>$ does not change it direction, but changes in length, is presented. Such ``longitudinal'' excitations do not exist in regular magnets, dynamics of which are described in terms of the Landau-Lifshitz equation or by means of the spin Heisenberg Hamiltonian. We demonstrate the presence of non-linear uniform oscillations and waves, as well as self-localized dynamical excitations (solitons) with finite energy. A possibility of excitation of such oscillations by ultrafast laser pulse is discussed.

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B. A. Ivanov, A. Yu. Galkin, R. S. Khymyn, A. Yu. Merkulov. 2007-11-27. Non-linear dynamics and two-dimensional solitons for spin $ S=1$ ferromagnets with biquadratic exchange. https://doi.org/10.1103/physrevb.77.064402

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