Browsing by Author "Zanardo, J"

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    Chemical disorder in a frustrated J1/J2 quantum spin chain material
    (Australian Institute of Physics, 2018-01-30) Rule, KC; Mole, RA; Zanardo, J; Krause-Heuer, AM; Darwish, TA; Lerch, MLF
    Recently a new one-dimensional (1D) quantum spin chain system has been synthesised: catena-dichloro(2-Cl-3Mpy)copper(II), [where 2-Cl-3Mpy=2-chloro-3-methylpyridine]. We shall refer to this compound as cd-Cu. Preliminary calculations and bulk magnetic property measurements indicate that this system does not undergo magnetic ordering down to 1.8K and is a prime candidate for investigating frustration in a J1/J2 system (where the nearest neighbour interactions, J1, are ferromagnetic and the next nearest neighbour interactions, J2, are antiferromagnetic) [1]. Calculations predicted 3 possible magnetic interaction strengths for J1 below 6meV depending on the orientation of the ligand [2]. For one of the predicted J1values, the existence of a quantum critical point is implied. A deuterated sample of cd-Cu was produced at the National Deuteration Facility and the excitations measured using the PELICAN TOF spectrometer. Scattering was weak from this sample, but indicated the most likely scenario involves an average of the 3 possible magnetic excitations in this material, rather than the random array of exchange interactions as predicted by Herringer et al., [2]. This may indicate the possibility of tuning the chemical structure to favour a system which may exhibit a quantum critical point.
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    Crystal growth and characterisation of a new J1-J2 spin-chain material
    (Australian Institute of Nuclear Science and Engineering, 2016-11-29) Zanardo, J; Rule, KC; Krause-Heuer, AM; Mole, RA; Lerch, MLF
    Recently a new one-dimensional (1D) quantum spin chain system has been synthesised: catena-dichloro(2-Cl-3Mpy)copper(II), [where 2-Cl-3Mpy=2-chloro-3-methylpyridine] [1]. Preliminary calculations and bulk magnetic property measurements indicate that this system does not undergo magnetic ordering down to 1.8K and is a prime candidate for investigating frustration in a J1/J2 system (where the next nearest neighbour interactions, J2, are antiferromagnetic and the nearest neighbour interactions, J1, are ferromagnetic) [2]. Calculations predict 3 possible magnetic excitations below 6meV which may reveal the nature of the random static structural disorder predicted in this material. One method for directly observing the magnetic excitations is neutron scattering and measurements have been performed on the neutron Time of Flight spectrometer PELICAN at ANSTO [3]. To a first approximation, linear spin-wave theory has been used to model the expected neutron excitations for this J2/J1 system using the Matlab package SpinW. The results of this project may provide valuable insight into the nature of magnetic frustration in materials. To optimise the observed magnetic signal via the reduction of incoherent neutron scattering, this compound was deuterated at the National Deuteration Facility at ANSTO. In this presentation we will outline our deuterated growth procedure as well as the characterisation methods performed to understand the material further. This work forms the Honours thesis project of Jack Zanardo from University of Wollongong.