Power-law spin correlations in pyrochlore antiferromagnets

Abstract

The ground state ensemble of the highly frustrated pyrochlore-lattice antiferromagnet can be mapped to a coarse-grained ``polarization'' field satisfying a zero-divergence condition From this it follows that the correlations of this field, as well as the actual spin correlations, decay with separation like a dipole-dipole interaction ($1/|R|^3$). Furthermore, a lattice version of the derivation gives an approximate formula for spin correlations, with several features that agree well with simulations and neutron-diffraction measurements of diffuse scattering, in particular the pinch-point (pseudo-dipolar) singularities at reciprocal lattice vectors. This system is compared to others in which constraints also imply diffraction singularities, and other possible applications of the coarse-grained polarization are discussed.Comment: 13 pp, revtex, two figure

Spin correlations in the dipolar pyrochlore antiferromagnet Gd2Sn2O7

“…It is interesting to compare our results for Gd 2 Sn 2 O 7 with a model containing nearest-neighbour Heisenberg exchange interactions only (i.e., D = 0 and ∆ = 0 in (7)). This model is a paradigm of frustrated magnetism: its scattering pattern shows "pinch point" features and does not show rods of diffuse scattering [8,9,41,42]. Our Monte Carlo simulations of this model at T J reveal that it shows much smaller ratios of 2.733(9) and 0.732(7), respectively.…”

Nonmonotonic residual entropy in diluted spin ice: A comparison between Monte Carlo simulations of diluted dipolar spin ice models and experimental results

“…[47][48][49]57 Spin ices thus appear to be ideal systems to investigate quantitatively the effects of random disorder in a highly frustrated magnetic setting. 49,57,58 In this paper we reported results from Monte Carlo simulations of a site-diluted version of the dipolar spin ice model (DSIM) given by Eq.…”

“…This model possesses a Pauling residual entropy, S P , 46 and displays at zero temperature an ice-rule obeying ground state characterized by dipolar-like spin-spin correlations that emerge from the "two-in/two-out" ice rule constraint. [47][48][49] On the other hand, in real spin ice materials, the Dy 3+ and Ho 3+ ions carry a large magnetic moment (∼ 10 µ B ) and the long range dipolar interactions cannot be ignored. 30,31,50 Given the symmetry of the crystal field ground state, 8,15,16 the magnetic moments can be well described by vector spins constrained by the single-ion anisotropy to point strictly parallel or antiparallel to their respective local [111] direction (i.e., along the line from the corners to the centre of each tetrahedron).…”

Exotic topological order in fractal spin liquids

“…The following is a ground state: The Sierpinski triangle model has liquidlike order, but is different from conventional classical spin liquids such as antiferromagnetic Ising models on geometrically frustrated lattices. [28][29][30][31][32] Due to unconventional three-body interactions, the model does not have magnetic order at any temperature including T = 0. A zero-temperature thermodynamic entropy is large, but not extensive: S = √ N .…”