Browsing by Author "Ehlers, G"
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- ItemInelastic neutron scattering as a means for determining the magnetic exchange interactions in the frustrated quantum spin chain, Linarite(Australian Institute of Physics, 2021-02-02) Rule, KC; Willenberg, B; Mole, RA; Wolter-Giraud, A; Tennant, A; Ehlers, G; Studer, AJ; Gardner, J; Suellow, SOne of the simplest models exhibiting one dimensional (1D) frustrated quantum interactions is the so called J1-J2 model. In this model competing ferromagnetic nearest-neighbour interactions (J1 > 0) and antiferromagnetic next-nearest-neighbours (J2 < 0) can give rise to novel phenomena such as multiferroicity for spiral spin states. Linarite, PbCuSO4(OH)2 is a natural mineral ideally suited to the study of frustration in J1-J2 systems due to an accessible saturation field and the availability of large single crystals well suited to neutron investigations. In this material the Cu2+ ions form spin S = 1/2 chains along the b direction with dominant nearest-neighbour FM interactions and a weaker next-nearest-neighbour AFM coupling, resulting in a magnetically frustrated topology. We present a neutron scattering study of linarite revealing a helical magnetic ground state structure with an incommensurate propagation vector of (0, 0.186, ½) below TN = 2.8K in zero magnetic field. From detailed measurements in magnetic fields up to 12 T (B || b), a very rich magnetic phase diagram will be presented. In particular we will present new inelastic neutron scattering data and compare this with theoretical modelling of the spin Hamiltonian. These theoretical calculations imply that linarite possesses an xyz exchange anisotropy. Our data establish linarite as a model compound of the frustrated one-dimensional spin chain, with ferromagnetic nearest-neighbour and antiferromagnetic next-nearest-neighbour interactions.
- ItemLow energy spin dynamics in the spin ice Ho2Sn2O7(Intitite of Physics Publishing Ltd, 2012-02-22) Ehlers, G; Huq, A; Diallo, SO; Adriano, C; Rule, KC; Cornelius, AL; Fouquet, P; Pagliuso, PG; Gardner, JSThe magnetic properties of Ho 2 Sn 2 O 7 have been investigated and compared to other spin ice compounds. Although the lattice has expanded by 3% relative to the better studied Ho 2 Ti 2 O 7 spin ice, no significant changes were observed in the high temperature properties, T greater than or similar to 20 K. As the temperature is lowered and correlations develop, Ho 2 Sn 2 O 7 enters its quantum phase at a slightly higher temperature than Ho 2 Ti 2 O 7 and is more antiferromagnetic in character. Below 80 K a weak inelastic mode associated with the holmium nuclear spin system has been measured. The hyperfine field at the holmium nucleus was found to be ≈700 T. (c) 2012 IOP Publishing LTD