Magnetic correlations in deuteronium jarosite, a model S = 5/2 Kagomé antiferromagnet

Abstract

Deuteronium jarosite, (D 3 O)Fe 3 (SO 4 ) 2 (OD) 6 , contains a kagomé lattice of Heisenberg spins S=5/2 with a coverage of 97±1%. DC and AC susceptibility measurements show strong in-plane antiferromagnetic exchange (θ CW = -1500±300K) and a spin-glass transition at T f = 13.8K, while the magnetic contribution to the specific heat below T f rises with T as T 2 , characteristic of twodimensional propagating modes. Powder neutron diffraction reveals short-range magnetic correlations (ξ ≈ 19±2 Å) with a wavevector corresponding to the √3 x √3 spin structure at 1.9K. Numbers: (75.10Jm, 75.25.+x, 75.40Gb, 75.50Lk) PACS

Short-range order in the topological spin glass(D3O)Fe3(Wills1, Oakley2, Visser3 et al. 2001Phys. Rev. B417270View full textAdd to dashboardCite

“…However, the improved statistics afforded by polarization analysis and the extended Q range of the data have allowed a more accurate analysis of the diffuse scattering function, and the observation of significant short-range spin-spin correlations at 250 K, far higher than observed previously in unpolarized experiments. 3 We note that the spatial extent of the correlations at low temperature is found to be significantly less than formerly deduced from unpolarized experiments: at 1.5 K, the spin-spin correlation length corresponds to ϭ10Ϯ1 Å.…”

“…The improved signal-to-noise ratio that this leads to, when compared to unpolarized experiments, has enabled observation of magnetic correlations in (D 3 O)Fe 3 (SO 4 ) 2 (OD) 6 at higher temperatures and with greater accuracy than in previous experiments. 3 Their temperature dependence suggests that the spin-glass freezing transition is a consequence of two energy scales, as has been proposed for an anisotropy-induced glass transition in Refs. 13 and 14.…”

“…3 The solution was preheated in a PTFE lined stainless steel bomb at 70°C for 4 hours to solubilize the iron sulfate, before being heated at 155°C for 4 hours to precipitate the jarosite. After cooling, the ochre product was washed with D 2 O and dried in a vacuum furnace at 120°C.…”

“…In fact, the variety of exotic low-temperature physics exhibited in these lattices is astounding, e.g., topological spin glass, spin fluid, spin ice, colossal magnetoresistance, heavy fermion, and superconductivity. One particular area of interest involves the possibility of disorder-free spin-glass states, of the types observed in the kagomé antiferromagnet (H 3 O)Fe 3 (SO 4 ) 2 (OH) 6 [2][3][4][5][6][7][8][9][10][11][12] These spin-glass states are believed to be a consequence of the vertex sharing geometries, and they have been termed topological spin glasses in order to distinguish them from conventional sitedisordered systems. 13,14 In this article we report xyz polarized neutron-scattering measurements of a powder sample of the two-dimensional ͑2D͒ kagomé antiferromagnet (D 3 O)Fe 3 (SO 4 ) 2 (OD) 6 between 1.5 and 250 K. Unpolarized neutron-diffraction measurements of this material are hindered by the large background from strong nuclear Bragg reflections and incoherent scattering from protons present in partially deuterated samples.…”

“…26 The spin-glass state of the Sϭ5/2 kagomé antiferromagnet (D 3 O)Fe 3 (SO 4 ) 2 (OD) 6 has attracted interest recently due to its unconventional nature. [2][3][4]27,28 Rather than resulting from a competition between random superexchange paths, as is the situation in site-disordered spin glasses, this glassy magnetic phase exists in a system with only a small amount of disorder ͑the coverage of the magnetic lattice is ϳ97%) and it is possible that it is based on the interactions between topological defects. Remarkably, reduction in the coverage of the magnetic Fe lattice is found to first cause an increase in the freezing temperature T g and, if sufficient, to destabilize this glass-like state sufficiently for the formation of long-range Néel order with the qϭ0 spin configuration.…”