We have used neutron scattering to study spin chirality and high-field spin re-oriention in single crystal and powder samples of the antiferromagnetic kagom'e lattice compounds, AFe3(OH)6(SO4)2 (A = K and Ag). The 52 Fe^3+ spins on... more
We have used neutron scattering to study spin chirality and high-field spin re-oriention in single crystal and powder samples of the antiferromagnetic kagom'e lattice compounds, AFe3(OH)6(SO4)2 (A = K and Ag). The 52 Fe^3+ spins on the kagom'e lattice order three dimensionally for temperatures below the N'eel temperature, TN = 65 K. Above the N'eel temperature, we observed the spin
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The spin wave excitations of the S � 5=2 kagomelattice antiferromagnet KFe3� OH� 6� SO4� 2 have been measured using high-resolution inelastic neutron scattering. We directly observe a flat mode which corresponds to a lifted ''zero... more
The spin wave excitations of the S � 5=2 kagomelattice antiferromagnet KFe3� OH� 6� SO4� 2 have been measured using high-resolution inelastic neutron scattering. We directly observe a flat mode which corresponds to a lifted ''zero energy mode,'' verifying a fundamental prediction for the kagomelattice. A simple Heisenberg spin Hamiltonian provides an excellent fit to our spin wave data. The
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We have performed thermodynamic and neutron scattering measurements on the S=1/2 three-dimensional antiferromagnet clinoatacamite, Cu2(OH)3Cl. The crystal lattice feature Cu^2+ ions arranged on a distorted kagom'e lattice with weak... more
We have performed thermodynamic and neutron scattering measurements on the S=1/2 three-dimensional antiferromagnet clinoatacamite, Cu2(OH)3Cl. The crystal lattice feature Cu^2+ ions arranged on a distorted kagom'e lattice with weak magnetic coupling between adjacent planes. Long range magnetic order with a weak ferromagnetic moment emerges at the N'eel ordering temperature, TN = 6.2 K. The value of thetaCW is roughly 30
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An important challenge in condensed matter physics is the search for quantum spin liquid states in two dimensional frustrated systems. We have performed thermodynamic and neutron scattering measurements on the S=1/2 kagom'e lattice... more
An important challenge in condensed matter physics is the search for quantum spin liquid states in two dimensional frustrated systems. We have performed thermodynamic and neutron scattering measurements on the S=1/2 kagom'e lattice antiferromagnet ZnCu3(OH)6Cl2. The susceptibility indicates a Curie-Weiss temperature of thetaCW˜-300 K; however, no magnetic order is observed down to 50 mK. Inelastic neutron scattering reveals a spectrum
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Magnetic excitations of the pinwheel valence bond solid state in the distorted kagome lattice antiferromagnet Rb2Cu3SnF12 were studied using high-resolution inelastic neutron scattering. A weakly dispersive mode around 5 meV and duplicate... more
Magnetic excitations of the pinwheel valence bond solid state in the distorted kagome lattice antiferromagnet Rb2Cu3SnF12 were studied using high-resolution inelastic neutron scattering. A weakly dispersive mode around 5 meV and duplicate triplet excitations were observed. These modes cannot be reproduced by the dimer series expansion of six dimers, but are attributed to the folding of the two dimensional Brillouin zone caused by the structural transition. Polarization analysis of the excitations indicates that the transitions from the singlet state to the S_tot,z=+-1 and S_tot,z=0 triplet states are predominantly in-plane and out-of-plane polarized, respectively. Furthermore, continuum scattering was observed above 8 meV.
Magnetic properties of the $S = 1/2$ quasi-one-dimensional antiferromagnet $\alpha$-Cu$_{2}$V$_{2}$O$_{7}$ have been studied using magnetization and neutron scattering measurements. Magnetic susceptibility shows a broad peak at $\sim50$ K... more
Magnetic properties of the $S = 1/2$ quasi-one-dimensional antiferromagnet $\alpha$-Cu$_{2}$V$_{2}$O$_{7}$ have been studied using magnetization and neutron scattering measurements. Magnetic susceptibility shows a broad peak at $\sim50$ K followed by an abrupt increase indicative of a phase transition to a magnetically ordered state at $T_{N}$ = 33.4(1) K. Above $T_N$, a fit to the Curie-Weiss law gives a Curie-Weiss temperature of $\Theta=-73(1)$ K ($|J_{CW}|=6.3(1)$ meV), whereas the Bonner-Fisher fit yields the antiferromagnetic intra-chain coupling of $|J_{BF}|=2.99(2)$ meV. The discrepancy in the exchange interaction suggests a highly anisotropic network of spins with a sizable inter-chain interaction. Below $T_{N}$, weak ferromagnetism due to spin canting is observed. The canting is caused by the Dzyaloshinskii-Moriya interaction with an estimated $bc$-plane component $|D_p|$ of 0.420(3) meV. Neutron diffraction reveals that the $S=1/2$ Cu$^{2+}$ spins along a zigzag chain ant...
The deformed AFM kagome lattice Rb2Cu3SnF12 is the first realization of 'pinwheel' valence bond solid (VBS) ground state system [1]. Using inelastic neutron scattering technique, we mapped out the spin excitation spectrum up to 12... more
The deformed AFM kagome lattice Rb2Cu3SnF12 is the first realization of 'pinwheel' valence bond solid (VBS) ground state system [1]. Using inelastic neutron scattering technique, we mapped out the spin excitation spectrum up to 12 meV. The singlet to triplet transition is split by a substantial Dzyaloshinskii-Moriya (DM) interaction, with the energy gap at 2.4 meV (Sz= ± 1) and 6.9 meV (Sz = 0), respectively. While both excitations are non-dispersive to within 1.0 meV for wave vectors, qz, perpendicular to the kagome like plane, the intensity varies differently with qz for the two modes. This difference can be explained by the different polarization factor for Sz= ± 1 and Sz = 0 excitations. Under a magnetic field along the c-axis, the low energy gap persist near 1 meV for the fields between 9 T and 15 T. Our findings emphasize the important role of DM interaction in this material.[4pt] [1] K. Matan, T. Ono, Y. Fukumoto, T. J. Sato, J. Yamaura, M. Yano, K. Morita, and H. Tan...
The spin-1/2 kagome lattice antiferromagnet herbertsmithite, ZnCu(3)(OH)(6)Cl(2), 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... more
The spin-1/2 kagome lattice antiferromagnet herbertsmithite, ZnCu(3)(OH)(6)Cl(2), 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 chiT(alpha) with alpha approximately 0.66 can be expressed as a universal function of H/T or omega/T. This scaling is discussed in relation to similar behavior seen in systems influenced by disorder or by the proximity to a quantum critical point.
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We have studied the time-dependence of the compression of various materials under a constant external force. The materials range from thin sheets of Mylar (13 microns thick and up to 17.2 cm in radius) to porous tissue and to fibrous... more
We have studied the time-dependence of the compression of various materials under a constant external force. The materials range from thin sheets of Mylar (13 microns thick and up to 17.2 cm in radius) to porous tissue and to fibrous cotton balls. The material is placed in a cylindrical container where a fixed weight compresses the material by pushing down
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We have performed x-ray diffraction, magnetic susceptibility, and heat capacity measurements on TiOCl single crystals. Structurally TiOCl consists of buckled square lattice titanium-oxide layers separated by chlorine. Electronically, the... more
We have performed x-ray diffraction, magnetic susceptibility, and heat capacity measurements on TiOCl single crystals. Structurally TiOCl consists of buckled square lattice titanium-oxide layers separated by chlorine. Electronically, the titanium ions are in the d^1 configuration and have spin 1/2, similar to the undoped parent compounds of the superconducting cuprates. The susceptibility begins to drop around 100 K, followed by
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The Kagome lattice antiferromagnet is a prototypical geometrically frustrated spin system. We have performed magnetic susceptibility, heat capacity, and inelastic neutron scattering experiments on single crystal samples of the Kagome... more
The Kagome lattice antiferromagnet is a prototypical geometrically frustrated spin system. We have performed magnetic susceptibility, heat capacity, and inelastic neutron scattering experiments on single crystal samples of the Kagome lattice compound KFe_3(OH)_6(SO_4)_2. This material is composed of S=5/2 Kagome planes which are weakly coupled to each other. The spins order three-dimensionally below TM = 65 K, whereas the Curie-Weiss
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We have used inelastic neutron scattering to study spin-waves in single crystal samples of the antiferromagnetic kagome lattice compound, KFe_3(OH)_6(SO_4)_2. The 5/2 Fe^3+ spins on the kagome lattice order three dimensionally for... more
We have used inelastic neutron scattering to study spin-waves in single crystal samples of the antiferromagnetic kagome lattice compound, KFe_3(OH)_6(SO_4)_2. The 5/2 Fe^3+ spins on the kagome lattice order three dimensionally for temperatures below the Neel ...
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We have performed x-ray diffraction, magnetic susceptibility, and heat capacity measurements on TiOCl single crystals. Structurally TiOCl consists of buckled square lattice titanium-oxide layers separated by chlorine. However, due to... more
We have performed x-ray diffraction, magnetic susceptibility, and heat capacity measurements on TiOCl single crystals. Structurally TiOCl consists of buckled square lattice titanium-oxide layers separated by chlorine. However, due to ordering of the titanium orbitals, the magnetic system is characterized by 1-dimensional chains of spin-1/2 Ti ions. The susceptibility begins to drop around 100 K, followed by sharp drops at
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We have used neutron scattering to study spin chirality and high-field spin re-oriention in single crystal and powder samples of the antiferromagnetic kagom'e lattice compounds, AFe3(OH)6(SO4)2 (A = K and Ag). The 52 Fe^3+ spins... more
We have used neutron scattering to study spin chirality and high-field spin re-oriention in single crystal and powder samples of the antiferromagnetic kagom'e lattice compounds, AFe3(OH)6(SO4)2 (A = K and Ag). The 52 Fe^3+ spins on the kagom'e lattice order three dimensionally for temperatures below the N'eel temperature, TN = 65 K. Above the N'eel temperature, we observed the spin
Research Interests:
An important challenge in condensed matter physics is the search for quantum spin liquid states in two dimensional frustrated systems. We have performed thermodynamic and neutron scattering measurements on the S=1/2 kagom'e lattice... more
An important challenge in condensed matter physics is the search for quantum spin liquid states in two dimensional frustrated systems. We have performed thermodynamic and neutron scattering measurements on the S=1/2 kagom'e lattice antiferromagnet ZnCu3(OH)6Cl2. The susceptibility indicates a Curie-Weiss temperature of thetaCW˜-300 K; however, no magnetic order is observed down to 50 mK. Inelastic neutron scattering reveals a spectrum of low energy spin excitations with no observable gap down to 0.1 meV. The specific heat at low-T follows a power law with exponent alpha<=1. These results suggest that an unusual spin-liquid state with essentially gapless excitations is realized in this kagom'e lattice system.
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ABSTRACT
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Ghost modes and continuum scattering in the dimerized distorted kagome lattice antiferromagnet Rb<span class="aps-inline-formula"><math><msub><mrow></mrow><mn>2</mn></msub><
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Research Interests: Materials Engineering, Physics, Materials Science, Thermodynamics, Structural Materials, and 23 moreNanotechnology, Smart Materials, Multidisciplinary, Nature, Macromolecular X-Ray Crystallography, Magnetic field, Collective behaviour, Temperature, Nitrogen, Iron, Phase transition, Neutrons, Magnetics, Theoretical Models, Single Crystal, Low Temperature, Molecular Conformation, Neutron Scattering, Atoms, Nature Materials, Materials Testing, Beryllium, and Chemical Synthesis
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ABSTRACT
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We have performed thermodynamic and neutron scattering measurements on the S=1/2 three-dimensional antiferromagnet clinoatacamite, Cu$_{2}$(OH)$_{3}$Cl. The crystal lattice feature Cu$^{2+}$ ions arranged on a distorted kagom\'{e}... more
We have performed thermodynamic and neutron scattering measurements on the S=1/2 three-dimensional antiferromagnet clinoatacamite, Cu$_{2}$(OH)$_{3}$Cl. The crystal lattice feature Cu$^{2+}$ ions arranged on a distorted kagom\'{e} lattice with weak magnetic ...