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Title: Spin-Lattice Interaction in the Quasi-One-Dimensional Helimagnet LiCu2O2

Abstract

The field dependence of the electron spin resonance in a helimagnet LiCu{sub 2}O{sub 2} was investigated for the first time. In the paramagnetic state, a broad resonance line was observed corresponding to a g factor of 2.3. In the critical regime, around the paramagnetic to helimagnetic phase transition the resonance broadens and shifts to higher frequencies. A narrow signal is recovered at a low temperature, corresponding to a spin gap of 1.4 meV in zero field. A comprehensive model of the magnons is presented, using exchange parameters from neutron scattering and the spin anisotropy determined here. The role of the quantum fluctuations is discussed.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
913981
Report Number(s):
BNL-78549-2007-JA
Journal ID: ISSN 0031-9007; PRLTAO; TRN: US0801448
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys. Rev. Lett.; Journal Volume: 97
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ANISOTROPY; ELECTRON SPIN RESONANCE; FLUCTUATIONS; MAGNONS; NEUTRONS; RESONANCE; SCATTERING; SPIN; NSLS; national synchrotron light source

Citation Formats

Mihaly,L., Dora, B., Vanyolos, A., Berger, H., and Forro, L. Spin-Lattice Interaction in the Quasi-One-Dimensional Helimagnet LiCu2O2. United States: N. p., 2006. Web. doi:10.1103/PhysRevLett.97.067206.
Mihaly,L., Dora, B., Vanyolos, A., Berger, H., & Forro, L. Spin-Lattice Interaction in the Quasi-One-Dimensional Helimagnet LiCu2O2. United States. doi:10.1103/PhysRevLett.97.067206.
Mihaly,L., Dora, B., Vanyolos, A., Berger, H., and Forro, L. Sun . "Spin-Lattice Interaction in the Quasi-One-Dimensional Helimagnet LiCu2O2". United States. doi:10.1103/PhysRevLett.97.067206.
@article{osti_913981,
title = {Spin-Lattice Interaction in the Quasi-One-Dimensional Helimagnet LiCu2O2},
author = {Mihaly,L. and Dora, B. and Vanyolos, A. and Berger, H. and Forro, L.},
abstractNote = {The field dependence of the electron spin resonance in a helimagnet LiCu{sub 2}O{sub 2} was investigated for the first time. In the paramagnetic state, a broad resonance line was observed corresponding to a g factor of 2.3. In the critical regime, around the paramagnetic to helimagnetic phase transition the resonance broadens and shifts to higher frequencies. A narrow signal is recovered at a low temperature, corresponding to a spin gap of 1.4 meV in zero field. A comprehensive model of the magnons is presented, using exchange parameters from neutron scattering and the spin anisotropy determined here. The role of the quantum fluctuations is discussed.},
doi = {10.1103/PhysRevLett.97.067206},
journal = {Phys. Rev. Lett.},
number = ,
volume = 97,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • The one-dimensional anisotropic Heisenberg model in an external field is considered. For the corresponding energy operator with parameter h, the quasiclassical (h-O) spectral series are constructed using the method of the canonical operator. In the integrable case (in the absence of the external field) the results obtained coincide with the exact ones.
  • The Cu-NMR nuclear relaxation rate, {sup 63}(1/{ital T}{sub 1}) and Gaussian spin-echo decay rate, {sup 63}(1/{ital T}{sub 2{ital G}}) have been measured in order to investigate the low-energy spin dynamics in the quasi 1-D spin-1/2 antiferromagnetic (AF) cuprates such as Ca{sub 2}CuO{sub 3} with single chain, SrCuO{sub 2} at ambient pressure (AP) with zigzag chain coupled by weak ferromagnetic exchange interaction, SrCu{sub 2}O{sub 3} and Sr{sub 2}Cu{sub 3}O{sub 5} comprising of two- and three-leg ladder, respectively with isotropic AF exchange interaction along and between chains. In Ca{sub 2}CuO{sub 3}, 1/{ital T}{sub 1} stays constantly close to the 3D magnetic orderingmore » temperature, {ital T}{sub {ital N}} =10 K, dominated by dissipation of overdamped spinons gas as shown by Sachdev. By contrast, in AP-SrCuO{sub 2}, 1/{ital T}{sub 1} below 100 K decreases markedly down to the 3D magnetic ordering temperature, {ital T}{sub {ital N}} =3 K, providing a signature that the frustrated ferromagnetic interaction between CuO zigzag chains makes the spin gap open. In the spin-1/2 ladder compounds of SrCu{sub 2}O{sub 3} and Sr{sub 2}Cu{sub 3}O{sub 5} consisting of two- and three-leg, respectively, the former was demonstrated in the literatures to have the spin gap amounting to a half of AF exchange constant, {ital J}/2 where {ital J}=1300 K. For the latter, the magnetic coherence length, {xi}({ital T}) grows up according to {xi}({ital T}){approximately}1/({ital T}{minus}{theta}) and as a result, the magnetic ordering emerges around 50-60 K accompanying the divergence of 1/{ital T}{sub 1}. In the compounds composed of single and triple chains, it is shown that there is no analog of renormalized classical region identified in the 2D spin-1/2 cuprate such as La{sub 2}CuO{sub 4}, but the spin dynamics is in the quantum critical regime over wide {ital T} range due to the finite size of chains, even though the 3D magnetic ordering takes place at very low temperature.« less
  • Neutron scattering is used to study magnetic field induced ordering in the quasi-1D quantum spin-tube compound Sul-Cu2Cl4 that in zero field has a non-magnetic spin-liquid ground state. The experiments reveal an incommensurate chiral high-field phase stabilized by a geometric frustration of the magnetic interactions. The measured critical exponents \beta= 0.235 and \nu ~0.34 at Hc ~ 3.7 T point to an unusual sub-critical scaling regime and may reflect the chiral nature of the quantum critical point.
  • The dc ionic conductivity is calculated for one-dimensional (1-D) classical hopping with effects of nearest-neighbor repulsion included. Repulsion between ions in different channels which leads to three-dimensional ordering of the ions is accounted for in a mean-field manner. The intrachannel repulsion U is treated exactly by using results for the equivalent Ising antiferromagnet in a staggered field. It is shown that several choices can exist for the dependence of transition probabilities on nearest-neighbor occupation numbers and still satisfy detailed balance. In almost any case, however, the activation energy increases by U/2 as the temperature T goes through the ordering temperaturemore » T/sub c/ from above. An appreciable change in activation energy should then be observed in a 1-D superionic conductor which undergoes an order-disorder transition, provided this transition is triggered by interactions between the mobile ions. The dependence of activation energy upon U above T/sub c/ depends on the range of the forces and whether the hopping is purely classical or involves tunneling. We find that Kikuchi's result of a decrease in activation energy by U/2 from the noninteracting value is reproduced if very-short-range forces and classical activation over a barrier are assumed. On the other hand, we get Mahan's result of an increase by U/2 if the transition rate is governed by tunneling through a barrier.« less
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