Interacting spin-1/2 tetrahedral system Cu2Te2O5X2 (X = Cl, Br): a mean-field and random phase approximation analysis

TY - JOUR

T1 - Interacting spin-1/2 tetrahedral system Cu2Te2O5X2 (X = Cl, Br)

T2 - a mean-field and random phase approximation analysis

AU - Jensen, Jens

PY - 2009/1/7

Y1 - 2009/1/7

N2 - Magnetic ordering and excitations of Cu2Te2O5Cl2 are analyzed in terms of a tetramerized spin model for the tetrahedral Cu clusters of spin 1/2. The mean-field model is able to account for the main properties of the incommensurable magnetic structure observed by Zaharko et al. [Phys. Rev. B 73, 064422 (2006)]. The calculated excitation spectra show many similarities with the experimental neutron-scattering results. Close to a magnetic Bragg point at 2 K, the theory predicts the presence of a quasielastic phason mode and an inelastic amplitude mode at about 0.6 meV. This is in qualitative agreement with experimental observations of Prša et al., but the amplitude mode is observed at the much higher energy of about 2.5 meV. This discrepancy is puzzling since the tetrahedral Cu-spin system, in any other respect, behaves as a system of large local spins coupled with each other in a three-dimensional fashion. Preliminary model calculations for the Cu2Te2O5Br2 system lead to the same conclusion. Udgivelsesdato: 7. Januar

AB - Magnetic ordering and excitations of Cu2Te2O5Cl2 are analyzed in terms of a tetramerized spin model for the tetrahedral Cu clusters of spin 1/2. The mean-field model is able to account for the main properties of the incommensurable magnetic structure observed by Zaharko et al. [Phys. Rev. B 73, 064422 (2006)]. The calculated excitation spectra show many similarities with the experimental neutron-scattering results. Close to a magnetic Bragg point at 2 K, the theory predicts the presence of a quasielastic phason mode and an inelastic amplitude mode at about 0.6 meV. This is in qualitative agreement with experimental observations of Prša et al., but the amplitude mode is observed at the much higher energy of about 2.5 meV. This discrepancy is puzzling since the tetrahedral Cu-spin system, in any other respect, behaves as a system of large local spins coupled with each other in a three-dimensional fashion. Preliminary model calculations for the Cu2Te2O5Br2 system lead to the same conclusion. Udgivelsesdato: 7. Januar

U2 - 10.1103/PhysRevB.79.014406

DO - 10.1103/PhysRevB.79.014406

M3 - Journal article

SN - 0163-1829

VL - 79

SP - 014406

JO - Physical Review B Condensed Matter

JF - Physical Review B Condensed Matter

IS - 1

ER -