Classical fluctuations and anisotropy in quasi-one-dimensional antiferromagnets

Santini, P.; Domański, Zbigniew; Dong, Jiang; Erdös, Paul

doi:10.1103/physrevb.54.6327

Cited by 9 publications

(4 citation statements)

References 32 publications

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“…It has been suggested by Abarzhi et al [141] that quantum fluctuations are responsible for both these effects. This claim has bee supported by subsequent work [72,121] but recently has beem disputed by Santini et al [143], at least for CsMnBr 3 and RbMnBr 3 , where they claimed that the anisotropy is already present at the classical level, provided thermal fluctuations are taken into account. Santini's work is based on a Hamiltonian similar to (1) with the J ′ term replaced by a dipole-dipole interaction.…”

Section: The Case Of Large Anisotropy D > 3j ′mentioning

confidence: 91%

Review/Synthèse: Triangular antiferromagnets

Collins¹,

Petrenko²

1997

Can. J. Phys.

472

442

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In this article we review the effects of magnetic frustation in the stacked triangular lattice. Frustration increases the degeneracy of the ground state, giving rise to different physics. In particular it leads to unique phase diagrams with multicritical points and novel critical phenomena. We describe the confrontation of theory and experiment for a number of systems with differing magnetic Hamiltonians; Heisenberg, Heisenberg with easy-axis anisotropy, Heisenberg with easy-plane anisotropy, Ising and singlet ground state. Interestingly each leads to different magnetic properties and phase diagrams. We also describe the effects of ferromagnetic, rather than antiferromagnetic, stacking and of small distortions of the triangular lattice.

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Section: The Case Of Large Anisotropy D > 3j ′mentioning

confidence: 91%

Review/Synthèse: Triangular antiferromagnets

Collins¹,

Petrenko²

1997

Can. J. Phys.

472

442

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“…where we have added an Ising-like single-ion anisotropy term with constant D(< 0). Most of the intrachain couplings in ABX 3 compounds are antiferromagnetic such as in CsNiCl 3 or RbNiCl 3 with easy single-site anisotropy, or CsMnBr 3 and RbMnBr 3 with hard anisotropy [36,37]. These intrachain couplings can also be ferromagnetic (i.e., J < 0) as in CsNiF 3 [38,39] or CsCuCl 3 [40].…”

Section: Hexagonal Quasi-1d Abx3-type Antiferromagnetic Systemsmentioning

confidence: 99%

“…with A q and B q as given before by Eqs. (37). The structure factor within the linear spin-wave approximation is independent of s, and is given by Eq.…”

Section: Hexagonal Quasi-1d Abx3-type Antiferromagnetic Systemsmentioning

confidence: 99%

Longitudinal Excitations in Bipartite and Hexagonal Antiferromagnetic Spin Lattices

Xian

Merdan

2014

J. Phys.: Conf. Ser.

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Abstract. Based on our recently proposed magnon-density-waves using the microscopic manybody approach, we investigate the longitudinal excitations in quantum antiferromagnets by including the second order corrections in the large-s expansion. The longitudinal excitation spectra for a general spin quantum number using the antiferromagnetic Heisenberg Hamiltonian are obtained for various spin lattice models. For bipartite lattice models, we find that the numerical results for the energy gaps for the longitudinal modes at q → 0 and the magnetic ordering wavevector Q are reduced by about 40-50 % after including the second order corrections. Thus, our estimate of the energy gaps for the quasi-one-dimensional (quasi-1D) antiferromagnetic compound KCuF3 is in better agreement with the experimental result. For the quasi-1D antiferromagnets on hexagonal lattices, the full excitation spectra of both the transverse modes (i.e., magnons) and the longitudinal modes are obtained as functions of the nearest-neighbor coupling and the anisotropy constants. We find two longitudinal modes due to the non-collinear nature of the triangular antiferromagnetic order, similar to that of the phenomenological field theory approach by Affleck. We compare our results for the longitudinal energy gaps at the magnetic wavevectors with the experimental results for several antiferromagnetic compounds with both integer and non-integer spin quantum numbers, and also find good agreement after the higher-order contributions are included in our calculations. introductionThe dynamics of the two-dimensional (2D) and three-dimensional (3D) quantum antiferromagnetic systems with long-ranged order at low temperature can be considered as that of a dilute gas of weakly interacting spin-wave quasiparticles (magnons) with its density given by the quantum correction to the classical Néel order [1,2,3]. These magons are transverse modes with spin S = ±1. The longitudinal fluctuations with spin S = 0 present in these systems consist of the multi-magnon continuum [4]. The question concerning long-lived, well-defined longitudinal modes in quantum antiferromagnetic systems with long-ranged order remains open. This is our main focus in this paper.In case of the quantum antiferromagnetic systems without long-ranged order, the triplet excitation states (two transverse and one longitudinal) of the spin-1 Heisenberg chain with nonzero gap, first predicted by Haldane [5], are well known. This theoretical prediction of an energy gap separating the singlet ground state from the triplet excitation states has been confirmed experimentally in the quasi-1D antiferromagnetic compounds such as CsNiCl 3 and RbNiCl 3 of the spin-1 [6]. Some subsequent experimental investigations [7,6,8,9, 10] and theoretical calculations [11,12,13,14,3] also support Haldane's conjecture. In these experiments, the temperature is high enough so the quasi-1D systems have no long-ranged magnetic order and

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“…where the notation i, j indicates the nearest-neighbor couplings only and where we have also added an Ising-like singleion anisotropy term with constant D(< 0). Most of the intrachain couplings in ABX 3 compounds are antiferromagnetic such as in CsNiCl 3 or RbNiCl 3 with easy single-site anisotropy, or CsMnBr 3 and RbMnBr 3 with hard anisotropy [32,33]. These intrachain couplings can also be ferromagnetic (i.e., J < 0) as in CsNiF 3 [34,35] or CsCuCl 3 [36].…”

Section: The Spin-wave Theory Of the Anisotropic Hexagonal Antiferrom...mentioning

confidence: 99%

Excited states of quasi-one-dimensional hexagonal quantum antiferromagnets

Merdan

Xian

2013

Phys. Rev. B

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We investigate the excited states of the quasi-one-dimensional quantum antiferromagnets on hexagonal lattices, including the longitudinal modes based on the magnon-density waves. A model Hamiltonian with a uniaxial single-ion anisotropy is first studied by a spin-wave theory based on the one-boson method; the ground state thus obtained is employed for the study of the longitudinal modes. The full energy spectra of both the transverse modes (i.e., magnons) and the longitudinal modes are obtained as functions of the nearest-neighbor coupling and the anisotropy constants. We have found two longitudinal modes due to the non-collinear nature of the triangular antiferromagnetic order, similar to that of the phenomenological field theory approach by Affleck. The excitation energy gaps due to the anisotropy and the energy gaps of the longitudinal modes without anisotropy are then investigated. We then compare our results for the longitudinal energy gaps at the magnetic wavevectors with the experimental results for several antiferromagnetic compounds with both integer and noninteger spin quantum numbers, and we find good agreement after the higher-order contributions are included in our calculations.

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Classical fluctuations and anisotropy in quasi-one-dimensional antiferromagnets

Cited by 9 publications

References 32 publications

Review/Synthèse: Triangular antiferromagnets

Review/Synthèse: Triangular antiferromagnets

Longitudinal Excitations in Bipartite and Hexagonal Antiferromagnetic Spin Lattices

Excited states of quasi-one-dimensional hexagonal quantum antiferromagnets

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