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Full-Text Articles in Physics

Transitions To Valence-Bond Solid Order In A Honeycomb Lattice Antiferromagnet, Sumiran Pujari, Fabien Alet, Kedar Damle Mar 2015

Transitions To Valence-Bond Solid Order In A Honeycomb Lattice Antiferromagnet, Sumiran Pujari, Fabien Alet, Kedar Damle

Physics and Astronomy Faculty Publications

We use quantum Monte Carlo methods to study the ground-state phase diagram of a S=1/2 honeycomb lattice magnet in which a nearest-neighbor antiferromagnetic exchange J (favoring Néel order) competes with two different multispin interaction terms: a six-spin interaction Q3 that favors columnar valence-bond solid (VBS) order, and a four-spin interaction Q2 that favors staggered VBS order. For Q3Q2J, we establish that the competition between the two different VBS orders stabilizes Néel order in a large swath of the phase diagram even when J is the smallest energy scale in the Hamiltonian. When ...


Transverse Magnetism Of The Diluted Antiferromagnet Fe1-Xmgxbr2 (X=0.15), Christian Binek Mar 2012

Transverse Magnetism Of The Diluted Antiferromagnet Fe1-Xmgxbr2 (X=0.15), Christian Binek

Christian Binek

Neutron diffraction and magnetization measurements of the diluted crystal Fe1−xMgxBr2 (xnot, vert, similar0.15) were performed. Successive phase transitions at zero applied field at TN1not, vert, similar12 K and TN2not, vert, similar10 K were found. A previous transverse term ferromagnetic moment was detected just below TN2.


Kinetics Of Random-Field Induced Domains In The Two-Dimensional Ising Antiferromagnet Rb2co0.85mg0.15f4, Christian Binek Mar 2012

Kinetics Of Random-Field Induced Domains In The Two-Dimensional Ising Antiferromagnet Rb2co0.85mg0.15f4, Christian Binek

Christian Binek

The previous kinetics of the two-dimensional diluted Ising antiferromagnet Rb2Co0.85Mg0.15F4 is studied via the temporal relaxation of the field-induced magnetization after field cooling (FC) and zero-field cooling (ZFC), respectively, to T < TN = 75.2K. After FC different non-exponential decay laws indicate a crossover from domain reorientation to wall rearrangement at decreasing T. After ZFC rapidly saturating magnetization of naturally grown domain walls precedes the slow random-field-controlled disordering process.


Random-Field Critical And Spin-Flop Behavior Of The Anisotropic Heisenberg Antiferromagnet Fe0.9mg0.1br2 In Axial Magnetic Fields, Christian Binek Mar 2012

Random-Field Critical And Spin-Flop Behavior Of The Anisotropic Heisenberg Antiferromagnet Fe0.9mg0.1br2 In Axial Magnetic Fields, Christian Binek

Christian Binek

Faraday optical measurements on the dilute hexagonal antiferromagnet Fe0.85Mg0.15Br2 in an external axial field reveal a spin-flop phase line ending at a multicritical point (Tm=8.1 K, Hm=1050 kA m-1) and crossover from random-exchange to random-field Ising criticality with an exponent Phi =1.40+or-0.04 in the vicinity of TN=11.1 K. Cusp-like behaviour of the specific heat at TN is discussed in view of recent Monte Carlo results.


Two-Magnon Excitations Observed By Neutron Scattering In The Two-Dimensional Spin-5/2 Heisenberg Antiferromagnet Rb2mnf4, T. Huberman, R. Coldea, R. A. Cowley, D. A. Tennant, R. L. Leheny, Rebecca Christianson, C. D. Frost Sep 2011

Two-Magnon Excitations Observed By Neutron Scattering In The Two-Dimensional Spin-5/2 Heisenberg Antiferromagnet Rb2mnf4, T. Huberman, R. Coldea, R. A. Cowley, D. A. Tennant, R. L. Leheny, Rebecca Christianson, C. D. Frost

Rebecca J. Christianson

The low-temperature magnetic excitations of the two-dimensional spin- 52 square-lattice Heisenberg antiferromagnetRb2MnF4 have been probed using pulsed inelastic neutron scattering. In addition to dominant sharppeaks identified with one-magnon excitations, a relatively weak continuum scattering is also observed at higherenergies. This is attributed to neutron scattering by pairs of magnons and the observed intensities are consistentwith predictions of spin wave theory.


Discrete Breathers In A Nonlinear Electric Line: Modeling, Computation And Experiment, F. Palmero, Lars Q. English, J. Cuevas, R. Carretero-González, P. G. Kevrekidis Aug 2011

Discrete Breathers In A Nonlinear Electric Line: Modeling, Computation And Experiment, F. Palmero, Lars Q. English, J. Cuevas, R. Carretero-González, P. G. Kevrekidis

Faculty and Staff Publications By Year

We study experimentally and numerically the existence and stability properties of discrete breathers in a periodic nonlinear electric line. The electric line is composed of single cell nodes, containing a varactor diode and an inductor, coupled together in a periodic ring configuration through inductors and driven uniformly by a harmonic external voltage source. A simple model for each cell is proposed by using a nonlinear form for the varactor characteristics through the current and capacitance dependence on the voltage. For an electrical line composed of 32 elements, we find the regions, in driver voltage and frequency, where n-peaked breather solutions ...


Critical Dynamics Of A Spin-5/2 Two-Dimensional Isotropic Antiferromagnet, Rebecca J. Christianson, R. L. Leheny, R. J. Birgeneau, R. W. Erwin Jul 2011

Critical Dynamics Of A Spin-5/2 Two-Dimensional Isotropic Antiferromagnet, Rebecca J. Christianson, R. L. Leheny, R. J. Birgeneau, R. W. Erwin

Rebecca J. Christianson

We report a neutron-scattering study of the dynamic spin correlations in Rb2MnF4, a two-dimensional spin-5/2 antiferromagnet. By tuning an external magnetic field to the value for the spin-flop line, we reduce the effective spin anisotropy to essentially zero, thereby obtaining a nearly ideal two-dimensional isotropic antiferromagnet. From the shape of the quasielastic peak as a function of temperature, we demonstrate dynamic scaling for this system and find a value for the dynamical exponent z. We compare these results to theoretical predictions for the dynamic behavior of the two-dimensional Heisenberg model, in which deviations from z=1 provide a measure ...


Spin Correlations In An Isotropic Spin-5/2 Two-Dimensional Antiferromagnet, R. L. Leheny, Rebecca J. Christianson, R. J. Birgeneau, R. W. Erwin Jul 2011

Spin Correlations In An Isotropic Spin-5/2 Two-Dimensional Antiferromagnet, R. L. Leheny, Rebecca J. Christianson, R. J. Birgeneau, R. W. Erwin

Rebecca J. Christianson

We report a neutron scattering study of the spin correlations for the spin-5/2 two-dimensional antiferromagnet Rb2MnF4 in an external magnetic field. Choosing fields near the system’s bicritical point, we tune the effective anisotropy in the spin interaction to zero, constructing an ideal S ­ = 5/2 Heisenberg system. The correlation length and structure factor amplitude are closely described by the semiclassical theory of Cuccoli 'et al.' over a broad temperature range, but show no indication of approaching the low-temperature renormalized classical regime of the quantum nonlinear sigma model.


Critical Dynamics Of A Spin-5/2 Two-Dimensional Isotropic Antiferromagnet, Rebecca J. Christianson, R L. Leheny, R J. Birgeneau, R W. Erwin Jul 2011

Critical Dynamics Of A Spin-5/2 Two-Dimensional Isotropic Antiferromagnet, Rebecca J. Christianson, R L. Leheny, R J. Birgeneau, R W. Erwin

Rebecca J. Christianson

We report a neutron-scattering study of the dynamic spin correlations in Rb2MnF4, a two-dimensional spin-5/2 antiferromagnet. By tuning an external magnetic field to the value for the spin-flop line, we reduce the effective spin anisotropy to essentially zero, thereby obtaining a nearly ideal two-dimensional isotropic antiferromagnet. From the shape of the quasielastic peak as a function of temperature, we demonstrate dynamic scaling for this system and find a value for the dynamical exponent z. We compare these results to theoretical predictions for the dynamic behavior of the two-dimensional Heisenberg model, in which deviations from z=1 provide a measure ...


Transverse Magnetism Of The Diluted Antiferromagnet Fe1-Xmgxbr2 (X=0.15), Christian Binek Nov 2001

Transverse Magnetism Of The Diluted Antiferromagnet Fe1-Xmgxbr2 (X=0.15), Christian Binek

Christian Binek Publications

Neutron diffraction and magnetization measurements of the diluted crystal Fe1−xMgxBr2 (xnot, vert, similar0.15) were performed. Successive phase transitions at zero applied field at TN1not, vert, similar12 K and TN2not, vert, similar10 K were found. A previous transverse term ferromagnetic moment was detected just below TN2.


Kinetics Of Random-Field Induced Domains In The Two-Dimensional Ising Antiferromagnet Rb2co0.85mg0.15f4, Christian Binek Jan 1998

Kinetics Of Random-Field Induced Domains In The Two-Dimensional Ising Antiferromagnet Rb2co0.85mg0.15f4, Christian Binek

Christian Binek Publications

The previous kinetics of the two-dimensional diluted Ising antiferromagnet Rb2Co0.85Mg0.15F4 is studied via the temporal relaxation of the field-induced magnetization after field cooling (FC) and zero-field cooling (ZFC), respectively, to T < TN = 75.2K. After FC different non-exponential decay laws indicate a crossover from domain reorientation to wall rearrangement at decreasing T. After ZFC rapidly saturating magnetization of naturally grown domain walls precedes the slow random-field-controlled disordering process.


Local Magnetic Properties Of Antiferromagnetic Febr2, J. Peloth, R. A. Brand, Takele Seda, M. M. Pereira De Azevedo, W. Kleeman, Ch. Binek, J. Kushauer, D. Bertrand Dec 1995

Local Magnetic Properties Of Antiferromagnetic Febr2, J. Peloth, R. A. Brand, Takele Seda, M. M. Pereira De Azevedo, W. Kleeman, Ch. Binek, J. Kushauer, D. Bertrand

Physics & Astronomy

The antiferromagnet FeBr2 has been studied by Mössbauer spectroscopy in external fields both in the metamagnetic region below the multicritical temperature TMCP and in the second-order transition region above. The local magnetization shows that the metamagnetic transition occurs by spin flips, as in simple models. However, in the second-order transition region, the local magnetization of the sublattice oriented antiparallel to the external field varies continuously but remains parallel to the c axis. This can only be understood if the external magnetic field induces strong transversal spin precession of the moments on the antiparallel sublattice. This shows that the ...


Random-Field Critical And Spin-Flop Behavior Of The Anisotropic Heisenberg Antiferromagnet Fe0.9mg0.1br2 In Axial Magnetic Fields, Christian Binek Feb 1994

Random-Field Critical And Spin-Flop Behavior Of The Anisotropic Heisenberg Antiferromagnet Fe0.9mg0.1br2 In Axial Magnetic Fields, Christian Binek

Christian Binek Publications

Faraday optical measurements on the dilute hexagonal antiferromagnet Fe0.85Mg0.15Br2 in an external axial field reveal a spin-flop phase line ending at a multicritical point (Tm=8.1 K, Hm=1050 kA m-1) and crossover from random-exchange to random-field Ising criticality with an exponent Phi =1.40+or-0.04 in the vicinity of TN=11.1 K. Cusp-like behaviour of the specific heat at TN is discussed in view of recent Monte Carlo results.