Inelastic-neutron-scattering study of the spin dynamics in the Haldane-gap system Ni(C2H8N2)2NO2ClO4

L. P. Regnault, I. Zaliznyak, J. P. Renard, and C. Vettier
Phys. Rev. B 50, 9174 – Published 1 October 1994
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Abstract

We have investigated the spin dynamics of the nearly ideal one-dimensional S=1 antiferromagnet Ni(C2H8N2)2NO2ClO4 (NENP) by inelastic neutron scattering. The measurements have been performed as a function of both the wave vector (in the vicinity of the antiferromagnetic point q=π) and the magnetic field, for field configurations parallel (up to 5 T) or perpendicular to the chain axis (up to 10 T). Our experimental results at low temperature are in good quantitative agreement with most theoretical predictions (both analytical and numerical) established for the spin-1 Haldane-gap system in presence of finite orthorhombic anisotropy: nonmagnetic singlet ground state, three gaps in the excitation spectrum corresponding to the excited triplet (Δy0≊1.05 meV, Δx0≊1.23 meV, Δz0≊2.5 meV), finite correlation lengths at T=0 (ξxy/d≊8,ξz/d≊4) and unconventional field dependencies. The evolution with field of the various modes and their respective polarization have been determined experimentally and are compared to recent field-theory treatments of the S=1 anisotropic antiferromagnetic chain together with numerical calculations on finite-size systems. We present results concerning the field dependencies of the correlation lengths, both in field parallel and perpendicular to the chain axis, which are not fully understood from the existing theories.

  • Received 31 May 1994

DOI:https://doi.org/10.1103/PhysRevB.50.9174

©1994 American Physical Society

Authors & Affiliations

L. P. Regnault and I. Zaliznyak

  • Département de Recherche Fondamentale sur la Matière Condensée, Service de Physique Statistique, Magnétisme et Supraconductivite, Laboratoire de Magnétisme et Diffraction Neutronique, Centre d’Etudes Nucléaires, 38054 Genoble cedex 9, France

J. P. Renard

  • Institut d’Electronique Fondamentale, Bâtiment 220, Université de Paris-Sud, 91405 Orsay, France

C. Vettier

  • European Synchrotron Radiation Facility, Boîte Postale 220, 38043 Grenoble cedex, France

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Issue

Vol. 50, Iss. 13 — 1 October 1994

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