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Spin wave dispersion and magnons from short range order in tapiolite (FeTa2O6); a quasi-two-dimensional antiferromagnet

Hague, J. P.; Chung, E. M. L.; Visser, D.; Balakrishnan, G.; Clementyev, E.; Paul, D. McK. and Lees, M. R. (2005). Spin wave dispersion and magnons from short range order in tapiolite (FeTa2O6); a quasi-two-dimensional antiferromagnet. Journal of Physics: Condensed Matter, 17(46) pp. 7227–7235.

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We describe neutron inelastic scattering measurements of spin waves in the quasi-two-dimensional antiferromagnet FeTa2O6. The intrinsic spin wave dispersion for a single domain is deduced from linear spin wave theory and used to determine the intra-plane exchange coefficients. Almost dispersion-free excitations are observed along the c* direction perpendicular to the magnetic planes. This justifies the neglect of inter-plane coupling, which merely stabilizes the ordered configuration below TN. Spin wave theory yields values for the nearest neighbour and next nearest neighbour exchange constants on perpendicular diagonals of J = −0.040(9) meV, J'/J = 0.20(0), J''/J = 0.23(9), and the anisotropy parameter D = 0.31(8) meV. The large value of D shows an Ising-like spin configuration to be consistent with the experimental data. Measurements of the temperature dependence of the scattering show that magnetic excitations persist to at least 20 K (over two times TN) due to the extensive 2D short range order. This is a highly unusual result, and has consequences for the understanding of two-dimensional spin systems.

Item Type: Journal Article
ISSN: 0953-8984
Academic Unit/Department: Science > Physical Sciences
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Biomedical Research Network (BRN)
Item ID: 12287
Depositing User: James Hague
Date Deposited: 30 Jun 2009 08:46
Last Modified: 14 Jan 2016 17:24
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