Browsing by Author "Lançon, D"

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    The dynamics and critical properties of FePS3, an Ising-like twodimensional magnet on a honeycomb lattice
    (Australian Institute of Physics, 2014-02-05) Wildes, A; Rule, KC; Lançon, D; Hicks, T
    The MPS3 compounds (M = transition metal) are a family of materials where the M2+ ions lie in planes forming a honeycomb lattice. The planes are weakly bound by van der Waals forces and, when the M2+ carries a magnetic moment, the materials are good approximations of two-dimensional (2D) antiferromagnets. The FePS3 compound is of particular interest as it is a rare example of an Ising-like 2D magnet with honeycomb symmetry [1]. We have performed experiments with neutron scattering to investigate the magnon dynamics on both a powder [2] and, more recently, on a single crystal. We have further made extensive measurements of the critical dynamics of the compound. We will present our results, showing the magnon dispersion surface and the magnitudes of the exchange interactions along with the scaling behaviour of the magnetization and the anisotropy. The results will be contrasted with a sister compound, MnPS3, which is a good example of a Heisenberg-like 2D magnet. We will also discuss the possibilities for tricritical points and quantum phase transitions in this compound.
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    Magnetic structure and magnon dynamics of the quasi-two-dimensional antiferromagnet FePS 3
    (American Physical Society, 2016-12-07) Lançon, D; Walker, HC; Ressouche, E; Ouladdiaf, B; Rule, KC; McIntyre, GJ; Hicks, TJ; Rønnow, HM; Wildes, AR
    Neutron scattering from single crystals has been used to determine the magnetic structure and magnon dynamics of FePS3, an S=2 Ising-like quasi-two-dimensional antiferromagnet with a honeycomb lattice. The magnetic structure has been confirmed to have a magnetic propagation vector of kM=[0112] and the moments are collinear with the normal to the ab planes. The magnon data could be modeled using a Heisenberg Hamiltonian with a single-ion anisotropy. Magnetic interactions up to the third in-plane nearest neighbor needed to be included for a suitable fit. The best fit parameters for the in-plane exchange interactions were J1=1.46, J2=−0.04, and J3=−0.96 meV. The single-ion anisotropy is large, Δ=2.66 meV, explaining the Ising-like behavior of the magnetism in the compound. The interlayer exchange is very small, J′=−0.0073 meV, proving that FePS3 is a very good approximation to a two-dimensional magnet. ©2016 American Physical Society
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    Magnetic structure of the quasi-two-dimensional antiferromagnet NiPS 3
    (American Physical Society, 2015-12-07) Wildes, AR; Simonet, V; Ressouche, E; McIntyre, GJ; Avdeev, M; Suard, E; Kimber, SAJ; Lançon, D; Pepe, G; Moubaraki, B; Hicks, TJ
    The magnetic structure of the quasi-two-dimensional antiferromagnet NiPS3 has been determined by magnetometry and a variety of neutron diffraction techniques. The experiments show that the samples must be carefully handled, as gluing influences the magnetometry measurements while preferred orientation complicates the interpretation of powder diffraction measurements. Our global set of consistent measurements show numerous departures from previously published results. We show that the compound adopts a k = [010] antiferromagnetic structure with the moment directions mostly along the a axis, and that the paramagnetic susceptibility is isotropic. The critical behavior was also investigated through the temperature dependence of the magnetic Bragg peaks below the Néel temperature. ©2015 American Physical Society