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Competing magnetic interactions in geometrically frustrated magnets give rise to new forms of correlated matter, such as spin liquids and spin ices. Characterizing the magnetic structure of these states has been difficult due to the absence of long-range order. Here, we demonstrate that the spin Seebeck effect (SSE) is a sensitive probe of magnetic short-range order (SRO) in geometrically frustrated magnets. In low temperature (2 - 5 K) SSE measurements on a model frustrated magnet \mathrm{Gd_{3}Ga_{5}O_{12}}, we observe modulations in the spin current on top of a smooth background. By comparing to existing neutron diffraction data, we find that these modulations arise from field-induced magnetic ordering that is short-range in nature. The observed SRO is anisotropic with the direction of applied field, which is verified by theoretical calculation., Comment: 5 pages, 4 figures

We report the results of neutron scattering on a powder sample of Gd3Ga5O12 at high magnetic fields. We find that in high fields (B>1.8 T) the system is not fully polarized, but has a small canting of the moments induced by the dipolar interaction. We show that the degree of canting is accurately predicted by the standard Hamiltonian which includes the dipolar interaction. The inelastic scattering is dominated at large momentum transfers by a band of almost dispersionless excitations. We show that these correspond to the spin waves localized on ten site rings, expected for a system described by a nearest neighbor interaction, and that the spectrum at high fields B>1.8 T is well-described by a spin wave theory. The phase for fields, 5 pages, 4 figures

We study the effect of varying the boundary condition on the spectral function of a finite 1D Hubbard chain, which we compute using direct (Lanczos) diagonalization of the Hamiltonian. By direct comparison with the two-body response functions and with the exact solution of the Bethe Ansatz equations, we can identify both spinon and holon features in the spectra. At half-filling the spectra have the well-known structure of a low energy holon band and its shadow---which span the whole Brillouin zone---and a spinon band present for momenta less than the Fermi momentum. New features related to the twisted boundary condition are cusps in the spinon band. We show that the spectral building principle, adapted to account for both the finite system size and the twisted boundary condition, describes the spectra well in terms of single spinon and holon excitations. We argue that these finite-size effects are a signature of spin-charge separation and that their study should help establish the existence and nature of spin-charge separation in finite-size systems., 8 pages, 6 figures

The Green's function for a hole moving in an antiferromagnet is derived analytically in the long-wavelength limit. We find that the infrared divergence is eliminated in two and higher dimensions so that the quasiparticle weight is finite. Our results also suggest that the hole motion is polaronic in nature with a bandwidth proportional to $t/J \exp [-c (t/J)^2] $ ($c$ is a constant). The connection of the long-wavelength approximation to the first-order approximation in the cumulant expansion is also clarified., 12 papes, 2 figures available upon request, revtex