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Title: Phase Diagram and Spin Hamiltonian of Weakly-coupled Anisotropic S=1/2 Chains in CuCl 2 .2((CD 3) 2SO)

Abstract

Field-dependent specific heat and neutron scattering measurements were used to explore the antiferromagnetic S=(1/2) chain compound CuCl{sub 2}{center_dot}2((CD{sub 3}){sub 2}SO). At zero field the system acquires magnetic long-range order below T{sub N}=0.93 K with an ordered moment of 0.44{micro}{sub B}. An external field along the b axis strengthens the zero-field magnetic order, while fields along the a and c axes lead to a collapse of the exchange stabilized order at {micro}{sub 0}H{sub c}=6 T and {micro}{sub 0}H{sub c}=4 T (extrapolated to zero temperature) and the formation of an energy gap in the excitation spectrum. We relate the field-induced gap to the presence of a staggered g-tensor and Dzyaloshinskii-Moriya interactions, which lead to effective staggered fields for magnetic fields applied along the a and c axes. Competition between anisotropy, interchain interactions, and staggered fields leads to a succession of three phases as a function of field applied along the c axis. For fields greater than {micro}{sub 0}H{sub c}, we find a magnetic structure that reflects the symmetry of the staggered fields. The critical exponent, beta, of the temperature driven phase transitions are indistinguishable from those of the three-dimensional Heisenberg magnet, while measurements for transitions driven by quantum fluctuations produce larger valuesmore » of beta.« less

Authors:
 [1];  [2];  [1];  [3];  [1];  [4]
  1. Johns Hopkins University
  2. ORNL
  3. Los Alamos National Laboratory (LANL)
  4. Brookhaven National Laboratory (BNL)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); High Flux Isotope Reactor
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931971
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review B; Journal Volume: 75
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ANISOTROPY; CHAINS; ENERGY GAP; EXCITATION; FLUCTUATIONS; HAMILTONIANS; MAGNETIC FIELDS; NEUTRONS; PHASE DIAGRAMS; SCATTERING; SPECIFIC HEAT; SPIN; SYMMETRY

Citation Formats

Chen, Y., Stone, Matthew B, Kenzelmann, M., Batista, C. D., Reich, D. H., and Broholm, C. L. Phase Diagram and Spin Hamiltonian of Weakly-coupled Anisotropic S=1/2 Chains in CuCl2.2((CD3)2SO). United States: N. p., 2007. Web. doi:10.1103/PhysRevB.75.214409.
Chen, Y., Stone, Matthew B, Kenzelmann, M., Batista, C. D., Reich, D. H., & Broholm, C. L. Phase Diagram and Spin Hamiltonian of Weakly-coupled Anisotropic S=1/2 Chains in CuCl2.2((CD3)2SO). United States. doi:10.1103/PhysRevB.75.214409.
Chen, Y., Stone, Matthew B, Kenzelmann, M., Batista, C. D., Reich, D. H., and Broholm, C. L. Mon . "Phase Diagram and Spin Hamiltonian of Weakly-coupled Anisotropic S=1/2 Chains in CuCl2.2((CD3)2SO)". United States. doi:10.1103/PhysRevB.75.214409.
@article{osti_931971,
title = {Phase Diagram and Spin Hamiltonian of Weakly-coupled Anisotropic S=1/2 Chains in CuCl2.2((CD3)2SO)},
author = {Chen, Y. and Stone, Matthew B and Kenzelmann, M. and Batista, C. D. and Reich, D. H. and Broholm, C. L.},
abstractNote = {Field-dependent specific heat and neutron scattering measurements were used to explore the antiferromagnetic S=(1/2) chain compound CuCl{sub 2}{center_dot}2((CD{sub 3}){sub 2}SO). At zero field the system acquires magnetic long-range order below T{sub N}=0.93 K with an ordered moment of 0.44{micro}{sub B}. An external field along the b axis strengthens the zero-field magnetic order, while fields along the a and c axes lead to a collapse of the exchange stabilized order at {micro}{sub 0}H{sub c}=6 T and {micro}{sub 0}H{sub c}=4 T (extrapolated to zero temperature) and the formation of an energy gap in the excitation spectrum. We relate the field-induced gap to the presence of a staggered g-tensor and Dzyaloshinskii-Moriya interactions, which lead to effective staggered fields for magnetic fields applied along the a and c axes. Competition between anisotropy, interchain interactions, and staggered fields leads to a succession of three phases as a function of field applied along the c axis. For fields greater than {micro}{sub 0}H{sub c}, we find a magnetic structure that reflects the symmetry of the staggered fields. The critical exponent, beta, of the temperature driven phase transitions are indistinguishable from those of the three-dimensional Heisenberg magnet, while measurements for transitions driven by quantum fluctuations produce larger values of beta.},
doi = {10.1103/PhysRevB.75.214409},
journal = {Physical Review B},
number = ,
volume = 75,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Sulfur dioxide reacts with [PPN]{sub 2}[MFe{sub 3}(CO){sub 14}] (M = Cr, Mo, W) (PPN = bistriphenylphosphonium iminium) to produce [PPN]{sub 2}[Fe{sub 3}(CO){sub 9}({mu}{sub 3},{eta}{sup 2}-SO{sub 2})] (1) and [PPN]{sub 2}[Fe{sub 3}(CO){sub 8}({mu}-SO{sub 2}){mu}{sub 3}-S] (2), which were characterized by infrared spectroscopy, {sup 13}C NMR, and X-ray crystallography. Further reaction of 1 with sulfur dioxide results in the formation of 2 in 48% yield. Reaction of SO{sub 2} with [PPN]{sub 2}[Fe{sub 4}(CO){sub 13}] yields [PPN]{sub 2}[Fe{sub 2}(CO){sub 6}({mu}-SO{sub 2}){sub 2}] (3) which was characterized by infrared spectroscopy, {sup 13}C NMR, mass spectrometry, and X-ray crystallography. One equivalent of sulfur dioxide withmore » [PPN]{sub 2}[MFe{sub 3}(CO){sub 14}C] (M = Cr, W) produces [PPN]{sub 2}[Fe{sub 3}(CO){sub 8}({mu}-SO{sub 2})-({mu}{sub 3}-CCO)] (4), which on further reaction with SO{sub 2} gives the known cluster [PPN]{sub 2}[Fe{sub 3}(CO){sub 7}({mu}-SO{sub 2}){sub 2}({mu}{sub 3}-CCO)] (5). An excess of sulfur dioxide with [MFe{sub 3}(CO){sub n}C]{sup x{minus}} (M = Cr, W: n = 13, x = 2; M = Rh: n = 12, x = 1; M = Mn: n = 13, x = 1) produced 5 as the only identified product.« less
  • Extensive EPR measurements were carried out in the temperature range 100{endash}300 K. The room-temperature data indicate that Gd{sup 3+} ions substitute equally for R{sup 3+} ions at the two magnetically inequivalent sites in the unit cell, and that the site symmetry of the Gd{sup 3+} ion is monoclinic. The Gd{sup 3+} room-temperature spin-Hamiltonian parameters and linewidths were estimated. The phase transition temperatures (T{sub c}) were determined to be 175{plus_minus}1K (first order) in RbPr(SO{sub 4}){sub 2}{center_dot}4H{sub 2}O, 178.5{plus_minus}1K (first order) in RbNd(SO{sub 4}){sub 2}{center_dot}4H{sub 2}O, 232{plus_minus}0.5K (second order) in RbSm(SO{sub 4}){sub 2}{center_dot}4H{sub 2}O, and 230.5{plus_minus}0.5K (second order) in RbEu(SO{sub 4}){sub 2}{center_dot}4H{submore » 2}O. In RbPr(SO{sub 4}){sub 2}{center_dot}4H{sub 2}O and RbNd(SO{sub 4}){sub 2}{center_dot}4H{sub 2}O, the occurrence of the first-order phase transitions was deduced from abrupt changes in the behavior of the linewidth, zero-field splitting, and line positions, and coexistence of lines observed below and above T{sub c}. In addition, there were observed occurrences of two more phase transitions second order in nature in RbPr(SO{sub 4}){sub 2}{center_dot}4H{sub 2}O (T{sub c1}=261K, T{sub c2}=207.5K) and in RbNd(SO{sub 4}){sub 2}{center_dot}4H{sub 2}O (T{sub c1}=250K, T{sub c2}=219.5K); these were not as sharply defined as the preceding ones. Below T{sub c}, for all the crystals, the symmetry of the crystals was found to be lower than monoclinic, the four ions in the unit cell becoming magnetically inequivalent from each other. The observed second-order phase transitions in the four crystals were found to be in agreement with Landau theory of second-order phase transitions; the critical exponent was determined to be {beta}{congruent}0.51. {copyright} {ital 1997} {ital The American Physical Society}« less
  • We study the heat transport of S = 1/2 chain compound CuCl{sub 2}·2((CH{sub 3}){sub 2}SO) along the b axis (vertical to the chain direction) at very low temperatures. The zero-field thermal conductivity (κ) shows a distinct kink at about 0.9 K, which is related to the long-range antiferromagnetic (AF) transition. With applying magnetic field along the c axis, κ(H) curves also show distinct changes at the phase boundaries between the AF and the high-field disordered states. These results indicate a strong spin-phonon interaction and the magnetic excitations play a role in the b-axis heat transport as phonon scatterers.
  • New complexes, mer,trans,M(CO)/sub 3/(PR/sub 3/)/sub 2/(SO/sub 2/) (M = Mo,W; R = Ph,Cy,i-Pr) (I), cis,trans-Mo(CO)/sub 2/-(PPh/sub 3/)/sub 2/(SO/sub 2/)(L) (L = NCMe,py,CNCy,CN-t-Bu and CN(p-tolyl))(II), and (Mo(CO)/sub 2/(py)(PPh/sub 3/)(..mu..-SO/sub 2/))/sub 2/, have been prepared and characterized by infrared spectroscopy, /sup 17/O and /sup 31/P NMR spectroscopy, and X-ray crystallography. Syntheses for fac-Mo(CO)/sub 3/(n/sup 2/-SO/sub 2/)(LL) (LL = dppe,bpy,phen,2 py) have also been developed. Depending upon L, II has been found to coordinate SO/sub 2/ either in the S-bonded (n/sup 1/ planar) or O,S-bonded (n/sup 2/) geometries. Remarkably, for L = CNCy or CN-t-Bu, II has been found to contain, in themore » solid state, an apparent equimixture of both coordination types. Isomerization of fac-M(CO)/sub 3/(dppe)(n/sup 2/-SO/sub 2/) (M=Mo,w; dppe = 1,2-bis(diphenylphosphino)ethane) to an n/sup 1/-planar SO/sub 2/ form, mer-M(CO)/sub 3/(dppe)(SO/sub 2/), has also been found to occur. Thus, control of the SO/sub 2/ coordination geometry has been achieved by varying either the electronic properties of the ancillary ligands or their disposition with respect to the SO/sub 2/. The X-ray crystal structure of mer,trans-Mo(CO)/sub 3/(P-i-Pr/sub 3/)/sub 2/(SO/sub 2/) revealed n/sup 1/-planar SO/sub 2/ binding, the first example of this geometry for group 6 metals. The M-S distance, 2.239 (3) angstrom, is the longest such distance for this geometry recorded to date. Crystal data: Pbca, Z=8, a=24.712(8) angstrom, b=16.033(6) angstrom, c=14.058(5) angstrom, R=0.079 for 2934 reflections with Igreater than or equal to2sigma(I). The structure of (Mo(CO)/sub 2/(py)(PPh/sub 3/)(..mu..-SO/sub 2/))/sub 2/ showed a novel SO/sub 2/ bridging geometry in which all three atoms of SO/sub 2/ are metal coordinated. Crystal data: P1, Z=1, a=14.883(4) angstrom, b=9.264(2) angstrom, c=10.808(2) angstrom, R=0.039 for 3282 reflections with Igreater than or equal to2sigma(I).« less