Berlin 2008 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 13: Correlated Electrons: Low-dimensional Systems - Materials 1

TT 13.5: Talk

Tuesday, February 26, 2008, 10:30–10:45, H 2053

Spin dynamics in the plateau phase of the 1D distorted diamond chain azurite, Cu₃(CO₃)₂(OH)₂ — Kirrily Rule¹, Anja Wolter¹, •Stefan Süllow², Bernd Wolf³, Michael Lang³, Jürgen Schreuer⁴, and Alan Tennant¹ — ¹BENSC, HMI, 14109 Berlin — ²IPKM, TU Braunschweig, 38106 Braunschweig — ³Physikalisches Institut, J.W. Goethe-Universität Frankfurt, 60438 Frankfurt(M) — ⁴Ruhr-Universität Bochum, Bochum

Recently, azurite, Cu₃(CO₃)₂(OH)₂, has been described as an ideal example of a frustrated one-dimensional (1D) diamond-chain antiferromagnet [1]. A 1/3 magnetisation plateau has been observed in azurite for fields between 11 and 30T applied perpendicular to both the crystallographic b axis and Cu²⁺ chain direction. Here, we present a study by means of inelastic neutron scattering, which has been performed on a large single crystal of azurite in fields up to 14T applied perpendicular to the chain direction, viz. in the plateau phase. Our data in the plateau phase indicate that the magnetic excitations can be described by a dimer-monomer model with two distinct energy scales. The dispersion function of the monomer chain reveals an effective spin coupling of J_eff = 10.1(2) K, while the lowest Zeeman-split dimer branch has an effective dimer-dimer coupling of J_dimer = 1.8(1) K. We will discuss possible values for the exchange constants J₁, J₂ and J₃ of the diamond chain model to account for these observations, based on a perturbative approach.

[1] H. Kikuchi et al. Phys. Rev. Lett. 94 (2005) 227201