Browsing by Author "Kimber, SAJ"

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    Experimental observation and computational study of the spin-gap excitation in Ba3BiRu2O9
    (American Physical Society, 2016-11-01) Ling, CD; Huang, Z; Kennedy, BJ; Rols, S; Johnson, MR; Zbiri, M; Kimber, SAJ; Hudspeth, J; Adroja, DT; Rule, KC; Avdeev, M; Blanchard, PER
    Ba3BiRu2O9 is a 6H-type perovskite compound containing face-sharing octahedral M2O9 (M=Ir, Ru) dimers, which are magnetically frustrated at low temperatures. On cooling through T∗=176 K, it undergoes a pronounced magnetostructural transition, which is not accompanied by any change in space group symmetry, long-range magnetic ordering, or charge ordering. Here, we report the first direct evidence from inelastic neutron scattering that this transition is due to an opening of a gap in the excitation spectra of dimers of low-spin Ru4+ (S=1) ions. X-ray absorption spectroscopy reveals a change in Ru-Ru orbital overlap at T∗, linking the emergence of this spin-gap excitation to the magnetostructural transition. Ab initio calculations point to a geometrically frustrated magnetic ground state due to antiferromagnetic interdimer exchange on a triangular Ru2O9 dimer lattice. X-ray total-scattering data rule out long-range magnetic ordering at low temperatures, consistent with this geometrically frustrated model. ©2016 American Physical Society
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    Interlayer tuning of electronic and magnetic properties in honeycomb ordered Ag3LiRu2O6
    (Royal Society of Chemistry, 2010-10-07) Kimber, SAJ; Ling, CD; Jonathan, D; Morris, P; Chemseddine, A; Henry, PF; Argyriou, DN
    We report a switching of electronic, magnetic and lattice properties in honeycomb ruthenates by interlayer cation exchange. The new material Ag3LiRu2O6 was made by ion-exchange of the ordered Li/Ru honeycomb material Li2RuO3 in an AgNO3 melt at 200°C. Neutron powder diffraction and electron microscopy show that the Li/Ru order is preserved in the honeycomb layers, however, significant stacking disorder is found between layers. In contrast to Li2RuO3, which is insulating, dimerised and diamagnetic, Ag3LiRu2O6 has low electrical resistivity (0.01 ohm cm−1) and a large magnetic susceptibility at room temperature. This is attributed to the electronic influence of the highly polarisable interlayer Ag+ cation. The combination of two dimensionality, good conductivity and stacking disorder means this family of materials have potential for thermoelectric applications. © 2010, Royal Society of Chemistry
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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