Spin dynamics of layered triangular antiferromagnets with uniaxial anisotropy

Chaudhury, Ranjan

doi:10.1016/j.jmmm.2006.03.050

Cited by 7 publications

(4 citation statements)

References 9 publications

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“…This may require the utilization of purely numerical algorithms such as those based on classical equations of motion. 23 with matrix elements defined as (34) * Electronic address: eric@physics.mun.ca…”

Section: Numerical Resultsmentioning

confidence: 99%

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Surface spin dynamics of antiferromagnetically coupled frustrated triangular films

2007

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Results are presented for spin-wave dispersions in geometrically frustrated stacked triangular antiferromagnets with a thin film or semi-infinite geometry having either zero, easy-plane, or easyaxis anisotropy. Surface effects on the equilibrium spin configurations and excitation spectrum are investigated for the case of antiferromagnetically coupled films, serving to extend previous results on ferromagnetically coupled layers [E. Meloche et al., Phys. Rev. B 74, 094424 (2006)]. An operator equation of motion formalism is applied to systems which are quasi-one and quasi-two dimensional in character. In contrast to the case of ferromagnetically coupled films the new results show surface modes that are well separated in frequency from bulk excitations. Magnetic excitations in thin films with an even or an odd number of layers show qualitatively different behavior. These results are relevant for a wide variety of stacked triangular antiferromagnetics materials. PACS numbers: 75.30.Ds, 75.70.-i I. INTRODUCTION The significant amount of research effort devoted to the discovery and understanding of new aspects of geometrically frustrated magnetic systems in recent decades has been almost exclusively focused on the study of bulk properties. 1 Among such systems, a large number of materials have been identified which are realizations of the prototype frustrated triangular antiferromagnet (AF). In addition to the AF near-neighbor in-plane coupling, the vast majority of these systems are also characterized by AF coupling between stacked triangular layers, such as in most of the ABX 3 compounds. 2 Theoretical and experimental studies of magnetic excitations in these model materials have revealed important information on the nature of the fundamental interactions and exposed new types of spin-wave modes in the bulk systems. 3,4,5,6 Interest in surface effects on frustrated magnetic systems has been enhanced recently with where J i,j > 0 represents the intralayer nearest-neighbor AF exchange coupling and J ′ i,i ′ > 0 represents the interlayer AF exchange coupling. The effects of anisotropic exchange coupling are included through the parameters σ and σ ′ , and D i represents the strength of the single-ion anisotropy at a magnetic site labelled i. The Hamiltonian in Eq. (1) can used to describe systems characterized with easy-plane (D i > 0) and easy-axis (D i < 0) single-ion anisotropy.where the position vector ρ = (x, y) and the amplitudes S ± A1,n (k ) depend on the z coordinate through the layer index n. Similar expressions are defined for sites on sublattices B 1 , C 1 , A 2 , B 2 and C 2 . For a semi-infinite system the set of finite difference equations connecting the Fourier amplitudes may be expressed in supermatrix form as Mb = 0, where M is an ∞ × ∞ block-tridiagonal matrix defined as are considered. For simplicity, we outline the calculation of Q A (k , n). This quantity can be written in terms of the transverse spin-correlation functions S − A,n (t)S + A,n (t ′ ) k and S + A,n (t)S − A,n (t ′ ) k evaluated at equa...

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Section: Numerical Resultsmentioning

confidence: 99%

“…This may require the utilization of purely numerical algorithms such as those based on classical equations of motion. 23…”

Section: Discussionmentioning

confidence: 99%

Surface spin dynamics of antiferromagnetically coupled frustrated triangular films

2007

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“…We have attempted a modelling of the replication accompanied by tautomeric mutation in DNA, by constructing a quantum spin-pseudospin based model analogous to some of the well known models used in statistical mechanics and magnetism [3][4][5][6][7][10][11][12]. The idea has been to incorporate quantum fluctuations to the existing ordered structure in a double-stranded DNA and calculate the rates of various processes.…”

Section: Discussionmentioning

confidence: 99%

Tautomeric mutation: A quantum spin modelling

Chaudhury¹

2007

Europhys. Lett.

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“…where g L is the Landé factor and μ B is the Bohr magneton. The model can be readily generalized to consider other lattice structures and geometries, including simple antiferromagnetic structures, 33,34 as well as other types of anisotropic interactions, such as axial anisotropy, anisotropic exchange, and the Dzyaloshinkii-Moryia interaction.…”

Section: Small-amplitude Spin Waves In Ferromagnetic Filmsmentioning

confidence: 99%

Dipole-exchange spin waves in magnetic thin films at zero and finite temperature: Theory and simulations

et al. 2011

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The excitation spectra in a stacked square lattice of dipole-exchange coupled classical spins is studied using both standard linearized spin-wave theory and the direct integration of the torque equation. A detailed comparison of the two methods is presented for the case of small-amplitude spin-wave modes. The spin-wave frequencies obtained from the time-dependent correlation functions calculated by integrating the equation of motion are shown to be in excellent agreement with the results obtained from linearized spin-wave theory for both single-layer and multilayer films. Applying the numerical integration method, the finite-temperature correlation function is calculated using Monte Carlo spin dynamics for the case of a single-layer, dipole-exchange coupled system. Values for the frequencies, amplitudes, and decay constant of the spin-wave modes at finite temperature are calculated from a spectral analysis of the finite-temperature correlation function. It is shown that thermal fluctuations give rise to a softening of the spin-wave frequencies and an intrinsic damping of the spin-wave oscillations.

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Spin dynamics of layered triangular antiferromagnets with uniaxial anisotropy

Cited by 7 publications

References 9 publications

Surface spin dynamics of antiferromagnetically coupled frustrated triangular films

Surface spin dynamics of antiferromagnetically coupled frustrated triangular films

Tautomeric mutation: A quantum spin modelling

Dipole-exchange spin waves in magnetic thin films at zero and finite temperature: Theory and simulations

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