Browsing by Author "Ressouche, E"

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    The magnetic properties and structure of the quasi-two-dimensional antiferromagnet CoPS3
    (IOP Science, 2017-10-12) Wildes, AR; Simonet, V; Ressouche, E; Ballou, R; McIntyre, GJ
    The magnetic properties and magnetic structure are presented for CoPS3, a quasi-twodimensional antiferromagnet on a honeycomb lattice with a Néel temperature of TN ∼ 120 K. The compound is shown to have XY-like anisotropy in its susceptibility, and the anisotropy is analysed to extract crystal field parameters. For temperatures between 2K and 300K, no phase transitions were observed in the field-dependent magnetization up to 10 Tesla. Singlecrystal neutron diffraction shows that the magnetic propagation vector is k = (010) with the moments mostly along the a axis and with a small component along the c axis, which largely verifies the previously-published magnetic structure for this compound. The magnetic Bragg peak intensity decreases with increasing temperature as a power law with exponent 2β = 0.60 ± 0.01 for T > 0.9 TN. © 2017 IOP Publishing Ltd
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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
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    Neutron study of the magnetism in NiCl2•4SC(NH2)2
    (IOP Publishing Ltd., 2013-05-29) Tsyrulin, N; Batista, CD; Zapf, VS; Jaime, M; Hansen, BR; Niedermayer, C; Rule, KC; Habicht, K; Prokes, K; Kiefer, K; Ressouche, E; Paduan, A; Kenzelmann, M
    We study the strongly anisotropic quasi-one-dimensional S = 1 quantum magnet NiCl2 center dot 4SC(NH2)(2) using elastic and inelastic neutron scattering. We demonstrate that a magnetic field splits the excited doublet state and drives the lower doublet state to zero energy at a critical field H-c1. For H-c1 < H < H-c2, where H-c2 indicates the transition to a fully magnetized state, three-dimensional magnetic order is established with the AF moment perpendicular to the magnetic field. We mapped the temperature/magnetic field phase diagram, and we find that the total ordered magnetic moment reaches m(tot) = 2.1 mu(B) at the field mu H-0 = 6 T and is thus close to the saturation value of the fully ordered moment. We study the magnetic spin dynamics in the fully magnetized state for H > H-c2, and we demonstrate the presence of an AF interaction between Ni2+ on the two interpenetrating sublattices. In the antiferromagnetically ordered phase, the spin-waves that develop from the lower-energy doublet are split into two modes. This is most likely the result of the presence of the AF interaction between the interpenetrating lattices.© 2013 IOP Publishing LTD.
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    Ubiquity of amplitude-modulated magnetic ordering in the H − T phase diagram of the frustrated non-Fermi-liquid YbAgGe
    (American Physical Society, 2021-08-17) Larsen, CB; Canévet, E; Mazzone, DG; Rüegg, C; Fåk, B; McMorrow, DF; Ressouche, E; McIntyre, GJ; Bud'ko, SL; Canfield, PC; Zaharko, O
    YbAgGe contains a magnetic geometrically frustrated kagome-like lattice that also features significant local single-ion anisotropy. The electronic state is established by hybridization of 4f and conduction electrons leading to heavy electronic masses. The competition between these various interactions leads to nontrivial behavior under external magnetic field, including a sequence of magnetic phase transitions, non-Fermi-liquid states, and possibly a quantum critical point. We present a series of neutron diffraction experiments performed in the mK temperature range and under magnetic fields up to 8 T in the hexagonal plane, revealing the microscopic nature of the first four subsequent magnetic states of this phase diagram. The magnetic phases are associated with the propagation vectors k1 = (13 0 13) for H<2 T, k2 = (0 0 0.32) for 2 T < H<3 T, k1=(13 0 13) for 3 T < H<4.5 T, and k3=(0.1950.1950.38) for 4.5 T < H<7 T. Our structural refinements reveal a strong modulation of he magnetic moment amplitude in all phases. We observe that the ordered moments of the three magnetically different Yb sites become increasingly different in field, which complies with the principle local anisotropy directions relative to the field direction. While the ordered moments are aligned predominantly in the hexagonal lane, we also find a significant out-of-plane component and a ferromagnetic contribution above 2 T. We discuss possible scenarios that may evolve around the phase boundary at 4.5 T, which is associated with putative quantum criticality as identified by various bulk probes. We propose further steps that are required to better understand the microscopic interactions in this material. ©2021 American Physical Society