231 research outputs found
Polarized neutron scattering studies of the kagome lattice antiferromagnet KFe3(OH)6(SO4)2
We report polarized neutron scattering studies of spin-wave excitations and
spin fluctuations in the S=5/2 kagome lattice antiferromagnet KFe3(OH)6(SO4)2
(jarosite). Inelastic polarized neutron scattering measurements at 10 K on a
single crystal sample reveal two spin gaps, associated with in-plane and
out-of-plane excitations. The polarization analysis of quasi-elastic scattering
at 67 K shows in-plane spin fluctuations with XY symmetry, consistent with the
disappearance of the in-plane gap above the Neel temperature T_N = 65 K. Our
results suggest that jarosite is a promising candidate for studying the 2D XY
universality class in magnetic systems.Comment: 3 pages, 3 figures, Proceeding to the 7th International Workshop on
Polarized Neutrons for Condensed Matter Investigations and 2nd International
Symposium of Quantum Beam Science Directorat
Dynamic Scaling in the Susceptibility of the Spin-1\2 Kagome Lattice Antiferromagnet Herbertsmithite
The spin-1/2 kagome lattice antiferromagnet herbertsmithite,
ZnCu(OH)Cl, is a candidate material for a quantum spin liquid
ground state. We show that the magnetic response of this material displays an
unusual scaling relation in both the bulk ac susceptibility and the low energy
dynamic susceptibility as measured by inelastic neutron scattering. The
quantity with can be expressed as a
universal function of or . This scaling is discussed in
relation to similar behavior seen in systems influenced by disorder or by the
proximity to a quantum critical point.Comment: 5 pages, 3 figures v2: updated to match published version
Antiferromagnetism of SrFe2As2 studied by Single-Crystal 75As-NMR
We report results of 75As nuclear magnetic resonance (NMR) experiments on a
self-flux grown high-quality single crystal of SrFe2As2. The NMR spectra
clearly show sharp first-order antiferromagnetic (AF) and structural
transitions occurring simultaneously. The behavior in the vicinity of the
transition is compared with our previous study on BaFe2As2. No significant
difference was observed in the temperature dependence of the static quantities
such as the AF splitting and electric quadrupole splitting. However, the
results of the NMR relaxation rate revealed difference in the dynamical spin
fluctuations. The stripe-type AF fluctuations in the paramagnetic state appear
to be more anisotropic in BaFe2As2 than in SrFe2As2.Comment: 4 pages, 5 figures; discussion revised; accepted for publication in
J. Phys. Soc. Jp
Doping Dependence of Spin Dynamics in Electron-Doped Ba(Fe1-xCox)2As2
The spin dynamics in single crystal, electron-doped Ba(Fe1-xCox)2As2 has been
investigated by inelastic neutron scattering over the full range from undoped
to the overdoped regime. We observe damped magnetic fluctuations in the normal
state of the optimally doped compound (x=0.06) that share a remarkable
similarity with those in the paramagnetic state of the parent compound (x=0).
In the overdoped superconducting compound (x=0.14), magnetic excitations show a
gap-like behavior, possibly related to a topological change in the hole Fermi
surface (Lifshitz transition), while the imaginary part of the spin
susceptibility prominently resembles that of the overdoped cuprates. For the
heavily overdoped, non-superconducting compound (x=0.24) the magnetic
scattering disappears, which could be attributed to the absence of a hole
Fermi-surface pocket observed by photoemission.Comment: 6 pages, 5 figures, published versio
- …