Modification of the classical Heisenberg helimagnet by weak uniaxial anisotropy and magnetic field
- P.L. Kapitza Inst. for Physical Problems, Moscow (Russian Federation)
- L.D. Landau Inst. for Theoretical Physics, Moscow (Russian Federation)
A classical ground state of the isotropic Heisenberg spin Hamiltonian on a primitive Bravais lattice is known to be a single-Q plane helix. Additional uniaxial anisotropy and external magnetic field can greatly distort this structure by generating higher-order (at the wave vectors nQ) Fourier harmonics in the spatial spin configuration. These features are not captured within the usual formalism based on the Luttinger-Tisza theorem, when the classical ground state energy is minimized under the {open_quotes}weak{close_quotes} condition on the lengths of the spins. We discuss why the correct solution is lost in that approach and present another microscopic treatment of the problem. For easy-axis and easy-plane quadratic uniaxial anisotropy it allows one to find the classical ground state for general Q and for any orientation of the magnetic field considering the effect of anisotropy (but not the field) as a perturbation of the exchange structure. As a result, the classical ground state energy, the uniform magnetization, and the magnetic Bragg peak intensities that are measured in the experiments are calculated. 21 refs., 1 fig.
- OSTI ID:
- 274037
- Journal Information:
- Journal of Experimental and Theoretical Physics, Vol. 81, Issue 3; Other Information: PBD: Sep 1995; TN: Translated from Zhurnal Eksperimental`noi i Teoreticheskoi Fiziki; 108: No. 3, 1052-1063(Sep 1995)
- Country of Publication:
- United States
- Language:
- English
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