64 research outputs found
Candidate Quantum Spin Liquid in the Ce\textsuperscript{3+} Pyrochlore Stannate CeSnO
We report the low temperature magnetic properties of CeSnO, a
rare-earth pyrochlore. Our susceptibility and magnetization measurements show
that due to the thermal isolation of a Kramers doublet ground state,
CeSnO has Ising-like magnetic moments of
. The magnetic moments are confined to the local trigonal axes,
as in a spin ice, but the exchange interactions are antiferromagnetic. Below 1
K the system enters a regime with antiferromagnetic correlations. In contrast
to predictions for classical -Ising spins on the
pyrochlore lattice, there is no sign of long-range ordering down to 0.02 K. Our
results suggest that CeSnO features an antiferromagnetic liquid
ground state with strong quantum fluctuations.Comment: 6 pages, 4 figure
Absence of Long Range Magnetic Order in the La1.4Sr0.8Ca0.8Mn2O7 Bilayered Manganite
In this work we studied, by means of high-resolution neutron diffraction as a
function of temperature, the La1.4Sr0.8Ca0.8Mn2O7 bilayered manganite for two
different annealing treatments. Out data allowed us to shown, for the first
time, the absence of long-range magnetic order in this optimally doped
bilayered manganite where the A-site of the structure is doped with equal
proportions of different isovalent cations (Ca and Sr). The system, however,
presents defined IM transitions which suggest that the transport properties are
not linked to the evolution of long-range order and that two dimensional spin
ordering in the layers of the perovskite blocks may be sufficient to 'assist'
the hole hopping. Possible reason for the suppression of magnetic order induced
by the Ca doping is a size effect coupled to the cation size mismatch between
the Sr and Ca ions.Comment: 24 pages, 7 figure
Single crystal growth, structure and magnetic properties of Pr2Hf2O7 pyrochlore
Large single crystals of the pyrochlore Pr2Hf2O7 have been successfully grown
by the floating zone technique using an optical furnace equipped with high
power Xenon arc lamps. Structural investigations have been carried out by both
synchrotron X-ray and neutron powder diffraction to establish the
crystallographic structure of the materials produced. The magnetic properties
of the single crystals have been determined for magnetic fields applied along
different crystallographic axes. The results reveal that Pr2Hf2O7 is an
interesting material for further investigations as a frustrated magnet. The
high quality of the crystals produced make them ideal for detailed
investigations, especially those using neutron scattering techniques.Comment: Accepted for publication in J. Phys.: Condens. Matte
Structural Evolution of One-dimensional Spin Ladder Compounds Sr14-xCaxCu24O41 with Ca doping and Related Hole Redistribution Evidence
Incommensurate crystal structures of spin ladder series Sr14-xCaxCu24O41
(x=3, 7, 11, 12.2) were characterized by powder neutron scattering method and
refined using the superspace group Xmmm(00{\gamma})ss0 (equivalent to
superspace group Fmmm(0,0,1+{\gamma})ss0); X stands for non-standard centering
(0,0,0,0), (0,1/2,1/2,1/2), (1/2,1/2,0,0), (1/2,0,1/2,1/2)) with a modulated
structure model. The Ca doping effects on the lattice parameters, atomic
displacement, Cu-O distances, Cu-O bond angles and Cu bond valence sum were
characterized. The refined results show that the CuO4 planar units in both
chain and ladder sublattices become closer to square shape with an increase of
Ca doping. The Cu bond valence sum calculation provided new evidence for the
charge transfer from the chains to ladders (approximately 0.16 holes per Cu
from x=0 to 12.2). The charge transfer was attributed to two different
mechanisms: (a) the Cu-O bond distance shrinkage on the ladder; (b) increase of
the interaction between two sublattices, resulting in Cu-O bonding between the
chains and ladders. The low temperature structural refinement resulted in the
similar conclusion, with a slight charge backflow to the chains.Comment: 29 pages, 16 figures, submitted to physics review b, accepte
On the magnetic structures of 1:1:1 stoichiometric topological phases LnSbTe (Ln = Pr, Nd, Dy and Er)
LnSbTe (Ln - lanthanide) group of materials, belonging to ZrSiS/PbFCl
(P4/nmm) structure type, is a platform to study the phenomena originating from
the interplay between the electronic correlations, magnetism, structural
instabilities and topological electronic structure. Here we report a systematic
study of magnetic properties and magnetic structures of LnSbTe materials. The
studied materials undergo antiferromagnetic ordering at TN = 2.1 K (Ln = Er),
6.7 K (Ln = Dy), 3.1 K (Ln = Nd). Neutron powder diffraction reveals ordering
with k1 = (1/2 + d 0 0) in ErSbTe, k2 = (1/2 0 1/4) in NdSbTe. DySbTe features
two propagation vectors k2 and k4 = (0 0 1/2). No long-range magnetic order is
observed in PrSbTe down to 1.8 K. We propose the most probable models of
magnetic structures, discuss their symmetry and possible relation between the
electronic structure and magnetic ordering.Comment: 21 pages, 10 figure
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