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Magnetic susceptibility and spin dynamics of a polyoxovanadate cluster: A proton NMR study of a model spin tetramer

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posted on 09.08.2018, 10:36 by D. Procissi, A. Shastri, Ioannis RousochatzakisIoannis Rousochatzakis, M. Al Rifai, P. Kogerler, Marshall Luban, B.J. Suh, Ferdinando Borsa
We report susceptibility and nuclear magnetic resonance (NMR) measurements in a polyoxovanadate compound with formula (NHEt)3[VIV8VV4As8O40(H2O)]H2O = (V12). The magnetic properties can be described by considering only the central square of localized V4+ ions and treated by an isotropic Heisenberg Hamiltonian of four intrinsic spins 1/2 coupled by nearest-neighbor antiferromagnetic interaction with J17.6K. In this simplified description the ground state is nonmagnetic with ST = 0. The 1H NMR linewidth (full width at half maximum) data depend on both the magnetic field and temperature, and are explained by the dipolar interaction between proton nuclei and V4+ ion spins. The behavior of the nuclear spin-lattice relaxation rate T-11 in the temperature range (4.2–300 K) is similar to that of χT vs T and it does not show any peak at low temperatures contrary to previous observations in antiferromagnetic rings with larger intrinsic spins. The results are explained by using the general features of the Moriya formula and by introducing a single T-independent broadening parameter for the electronic spin system. From the exponential T dependence of T-11 at low T(2.5K < T < 4.2K) we have obtained a field dependent gap following the linear relation ΔNMR = Δ0 “ gπBH, with the gap Δ0 17.6K in agreement with the susceptibility data. Below 2.5 K the proton T-11 deviates from the exponential decrease indicating the presence of a small, almost temperature independent, but strongly field dependent, nuclear relaxation contribution, which we will investigate in detail in the near future. © 2004 American Physical Society.

History

School

  • Science

Department

  • Physics

Published in

Physical Review B - Condensed Matter and Materials Physics

Volume

69

Issue

9

Citation

PROCISSI, D. ... et al., 2004. Magnetic susceptibility and spin dynamics of a polyoxovanadate cluster: A proton NMR study of a model spin tetramer. Physical Review B - Condensed Matter and Materials Physics, 69: 094436.

Publisher

© American Physical Society (APS)

Version

AM (Accepted Manuscript)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Publication date

2004

Notes

This paper was accepted for publication in the journal Physical Review B - Condensed Matter and Materials Physics and the definitive published version is available at https://doi.org/10.1103/PhysRevB.69.094436

ISSN

1098-0121

eISSN

1550-235X

Language

en

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