Magnetic Order of the Hexagonal Rare Earth Manganite Dy(0.5)Y(0.5)MnO3

Hexagonal Dy(0.5)Y(0.5)MnO3, a multiferroic rare-earth manganite with geometrically frustrated antiferromagnetism, has been investigated with single-crystal neutron diffraction measurements. Below 3.4 K magnetic order is observed on both the Mn (antiferromagnetic) and Dy (ferrimagnetic) sublattices that is identical to that of undiluted hexagonal DyMnO3 at low temperature. The Mn moments undergo a spin reorientation transition between 3.4 K and 10 K, with antiferromagnetic order of the Mn sublattice persisting up to 70 K; the antiferromagnetic order in this phase is distinct from that observed in undiluted (h)DyMnO3, yielding a qualitatively new phase diagram not seen in other hexagonal rare-earth manganites. A magnetic field applied parallel to the crystallographic c axis will drive a transition from the antiferromagnetic phase into the low-temperature ferrimagnetic phase with little hysteresis.Comment: Six pages, four figures v2: Table I added, Figures 2 and 3 edited, text edited. August 24, 201

Numerical study of the thermodynamics of clinoatacamite

We study the thermodynamic properties of the clinoatacamite compound, Cu_2(OH)_3Cl, by considering several approximate models. They include the Heisenberg model on (i) the uniform pyrochlore lattice, (ii) a very anisotropic pyrochlore lattice, and (iii) a kagome lattice weakly coupled to spins that sit on a triangular lattice. We utilize the exact diagonalization of small clusters with periodic boundary conditions and implement a numerical linked-cluster expansion approach for quantum lattice models with reduced symmetries, which allows us to solve model (iii) in the thermodynamic limit. We find a very good agreement between the experimental uniform susceptibility and the numerical results for models (ii) and (iii), which suggests a weak ferromagnetic coupling between the kagome and triangular layers in clinoatacamite. We also study thermodynamic properties in a geometrical transition between a planar pyrochlore lattice and the kagome lattice.Comment: 7 pages, 7 figure

Synthesis and Characterization of Single Crystal Samples of Spin-1/21/2 Kagome Lattice Antiferromagnets in the Zn-Paratacamite Family Znx_{x}Cu4−x_{4-x}(OH)6_{6}Cl2_{2}

The Zn-paratacamite family, Zn$_{x}$Cu$_{4-x}$(OH)$_{6}$Cl$_{2}$ for $x \, \geq$ 0.33, is an ideal system for studying spin-1/2 frustrated magnetism in the form of antiferromagnetic Cu$^{2+}$ 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 $x$ = 1 member of the series displays a magnetic susceptibility that is slightly anisotropic at high temperatures with $\chi_{c} \, > \, \chi_{ab}$. Neutron and synchrotron x-ray diffraction experiments confirm the quality of these $x$ = 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

Muon-spin spectroscopy of the organometallic spin-1/2 kagome-lattice compound Cu(1,3-benzenedicarboxylate)

Using muon-spin resonance, we examine the organometallic hybrid compound Cu(1,3-benzenedicarboxylate) [Cu(1,3-bdc)], which has structurally perfect spin-1/2 copper kagome planes separated by pure organic linkers. This compound has antiferromagnetic interactions with Curie-Weiss temperature of −33 K. We found slowing down of spin fluctuations starting at T=1.8 K and that the state at T→0 is quasistatic with no long-range order and extremely slow spin fluctuations at a rate of 3.6 μs[superscript −1]. This indicates that Cu(1,3-bdc) behaves as expected from a kagome magnet and could serve as a model kagome compound.European Commission (under the Sixth Framework Program through the Key Action: Strengthening the European Research Area, Research Infrastructures, Contract No. RII3-CT-2004-506008)European Science FoundationIsrael U.S.A. Binational Science Foundatio