17 research outputs found
Refining the Spin Hamiltonian in the Spin-1/2 Kagome Lattice Antiferromagnet ZnCu(OH)Cl using Single Crystals
We report thermodynamic measurements of the S=1/2 kagome lattice
antiferromagnet ZnCu(OH)Cl, a promising candidate system with
a spin-liquid ground state. Using single crystal samples, the magnetic
susceptibility both perpendicular and parallel to the kagome plane has been
measured. A small, temperature-dependent anisotropy has been observed, where
at high temperatures and at
low temperatures. Fits of the high-temperature data to a Curie-Weiss model also
reveal an anisotropy. By comparing with theoretical calculations, the presence
of a small easy-axis exchange anisotropy can be deduced as the primary
perturbation to the dominant Heisenberg nearest neighbor interaction. These
results have great bearing on the interpretation of theoretical calculations
based on the kagome Heisenberg antiferromagnet model to the experiments on
ZnCu(OH)Cl.Comment: 4 pages, 4 figure
Interplay of thermal and quantum spin fluctuations on the kagome lattice
We present a Raman spectroscopic investigation of the Herbertsmithite
ZnCu3(OH)6Cl2, the first realization of a Heisenberg s=1/2 antiferromagnet on a
perfect kagome lattice. The magnetic excitation spectrum of this compound is
dominated by two components, a high temperature quasi elastic signal and a low
temperature, broad maximum. The latter has a linear low energy slope and
extends to high energy. We have investigated the temperature dependence and
symmetry properties of both signals. Our data agree with previous calculations
and point to a spin liquid ground state.Comment: 5 figure
Synthesis and Characterization of Single Crystal Samples of Spin- Kagome Lattice Antiferromagnets in the Zn-Paratacamite Family ZnCu(OH)Cl
The Zn-paratacamite family, ZnCu(OH)Cl for 0.33, is an ideal system for studying spin-1/2 frustrated magnetism in
the form of antiferromagnetic Cu kagome planes. Here we report a new
synthesis method by which high quality millimeter-sized single crystals of
Zn-paratacamite have been produced. These crystals have been characterized by
metal analysis, x-ray diffraction, neutron diffraction, and thermodynamic
measurements. The = 1 member of the series displays a magnetic
susceptibility that is slightly anisotropic at high temperatures with . Neutron and synchrotron x-ray diffraction experiments
confirm the quality of these = 1 single crystals and indicate no obvious
structural transition down to temperatures of T=2 K.Comment: 4 pages, 3 figures, accepted by PRB rapid communicatio
A Cu2+ (S = 1/2) Kagom\'e Antiferromagnet: MgxCu4-x(OH)6Cl2
Spin-frustrated systems are one avenue for inducing macroscopic quantum
states in materials. However, experimental realization of this goal has been
difficult because of the lack of simple materials and, if available, the
separation of the unusual magnetic properties arising from exotic magnetic
states from behavior associated with chemical disorder, such as site mixing.
Here we report the synthesis and magnetic properties of a new series of
magnetically frustrated materials, MgxCu4-x(OH)6Cl2. Because of the
substantially different ligand-field chemistry of Mg2+ and Cu2+, site disorder
within the kagom\'e layers is minimized, as directly measured by X-ray
diffraction. Our results reveal that many of the properties of these materials
and related systems are not due to disorder of the magnetic lattice but rather
reflect an unusual ground state.Comment: Accepted for publication in J. Am. Chem. Soc
Revealing the Softening-Melting Behaviors and Slag Characteristics of Vanadium-Titanium Magnetite Burden with Various MgO Addition
MgO addition plays an essential role in the blast furnace smelting process, including softening-melting characteristics and metallurgical properties of slag. In the present study, the effect of MgO distribution on the softening-melting characteristics and slag system of vanadium-titanium magnetite burden were explored by simulating BF conditions. The results show that the MgO flux addition significantly affects the crystallization temperature of slag-phase, the precipitated phase components, and slag viscosity. This indicates that appropriate MgO addition can improve the metallurgical properties of blast furnace slag effectively, thereby improving the softening-melting-dripping performance of the mixed burden. The V-Ti pellets with a MgO content higher than 2.40 wt% exhibit optimum metallurgical properties. With a constant MgO content in mixed burden, the softening-melting properties of composite burden could be improved effectively as the MgO partitioning scheme includes 1.90 wt% MgO in sinter and 3.02 wt% MgO in pellet