Field dependence of the magnetic spectrum in anisotropic and Dzyaloshinskii-Moriya antiferromagnets: I. Theory

Abstract

We consider theoretically the effects of an applied uniform magnetic field on the magnetic spectrum of anisotropic two-dimensional and Dzyaloshinskii-Moriya layered quantum Heisenberg antiferromagnets. The first case is relevant for systems such as the two-dimensional square lattice antiferromagnet Sr(2)CuO(2)Cl(2), while the later is known to be relevant to the physics of the layered orthorhombic antiferromagnet La(2)CuO(4). We first establish the correspondence betwenn the low-energy spectrum obtained within the anisotropic non-linear sigma model and by means of the spin-wave approximation for a standard easy-axis antiferromagent. Then, we focus on the field-theory approach to calculate the magnetic field dependence of the magnon gaps and spectral intensities for magnetic fields applied along the three possible crystallographic directions. We discuss the various possible ground states and their evolution with temperature for the different field orientations, and the occurrence of spin-flop transitions for fields perpendicular to the layers (transverse fields) as well as for fields along the easy axis (longitudinal fields). Measurements of the one-magnon Raman spectrum in Sr(2)CuO(2)Cl(2) and La(2)CuO(4) and a comparison between the experimental results and the predictions of the present theory will be reported in part II of this research work [L. Benfatto et al., cond-mat/0602664].

21 pages, 11 figures, final version. Part II of the present work is presented in cond-mat/0602664

References in corpus (2)

• Effects of an external magnetic field on the gaps and quantum corrections in an ordered Heisenberg antiferromagnet with Dzyaloshinskii-Moriya anisotropy
• Field dependence of the magnetic spectrum in anisotropic and Dzyaloshinskii-Moriya antiferromagnets: II. Raman spectroscopy

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• Field dependence of the magnetic spectrum in anisotropic and Dzyaloshinskii-Moriya antiferromagnets: II. Raman spectroscopy
• Competing impurities and reentrant magnetism in La(2-x)Sr(x)Cu(1-z)Zn(z)O(4) revisited. The role of the Dzyaloshinskii-Moriya and XY anisotropies
• Spin-flop transitions and spin-wave gaps in La_2CuO_4
• Thermal Hall conductivity of a valence bond solid phase in the square lattice $J_1$-$J_2$ antiferromagnet Heisenberg model with a Dzyaloshinskii-Moriya interaction
• Impurity susceptibility and the fate of spin-flop transitions in lightly-doped La(2)CuO(4)
• Quantum corrections to the spin-wave spectrum of La${}_2$CuO${}_4$ in an external magnetic field
• AC Hopping Magnetotransport Across the Spin Flop Transition in Lightly Doped La_2CuO_4