Phase diagram and spin Hamiltonian of weakly-coupled anisotropic S=½ chains in CuCl2·2((CD3)2SO)

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Title: Phase diagram and spin Hamiltonian of weakly-coupled anisotropic S=½ chains in CuCl2·2((CD3)2SO)
Author: Chen, Y.; Stone, M.B.; Kenzelmann, M.; Batista, C.D.; Reich, D.H.; Broholm, C.; Chen, Y.1; Stone, M.B.1; Kenzelmann, M.1; Batista, C.D.; Reich, D.H.; Broholm, C.
Abstract: Field-dependent specific heat and neutron scattering measurements were used to explore the antiferromagnetic S=½ chain compound CuCl2·2((CD3)2SO). At zero field the system acquires magnetic long-range order below TN=0.93 K with an ordered moment of 0.44μB. 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 μ0Hc=6 T and μ0Hc=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 μ0Hc, we find a magnetic structure that reflects the symmetry of the staggered fields. The critical exponent, β, 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 β.
Date: 2007-06-01
Citation: Physical Review B (Condensed Matter and Materials Physics) 1 June 2007, vol.75, no.21, pp. 214409/1-11
Subject: zero-field magnetic order
exchange stabilized order collapse
magnetic long-range order
neutron scattering
weakly-coupled anisotropic chain
Dzyaloshinskii-Moriya interaction
interchain interactions
phase transition
spin Hamiltonians
specific heat
magnetic moments
magnetic anisotropy
long-range order
Heisenberg model
staggered field symmetry
exchange interactions (electron)
energy gap
critical exponents
copper compounds
antiferromagnetic materials
three-dimensional Heisenberg magnet

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