Browsing by Author "Stewart, JR"

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    (3)He polarization for ISIS TS2 phase I instruments
    (Elsevier, 2011-06-01) Beecham, CJ; Boag, S; Frost, CD; McKetterick, TJ; Stewart, JR; Andersen, KH; Bentley, PM; Jullien, D
    Here we report on the development of polarization analysis (PA) techniques to be employed at the ISIS pulsed neutron source second target station. Both spin exchange optical pumping and metastability exchange optical pumping techniques are being developed at ISIS to produce polarized neutron spin filters for use as neutron polarizers and analysers. We focus on the developments of a polarization solution on the LET spectrometer, including the updated design of the PASTIS XYZ coil set and single crystal silicon analyser cell. We also report on the construction of a combined polarizer/analyser solution for the WISH diffractometer. (C) 2010 Elsevier B.V.
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    Emergent frustration in co-doped β-Mn
    (American Physical Society, 2013-06-28) Paddison, JAM; Stewart, JR; Manuel, P; Courtois, P; McIntyre, GJ; Rainford, BD; Goodwin, AL
    We investigate low-temperature spin correlations in the metallic frustrated magnet beta-Mn1-xCox. Single-crystal polarized-neutron scattering experiments reveal the persistence of highly structured magnetic diffuse scattering and the absence of periodic magnetic order to T = 0.05 K. We employ reverse Monte Carlo refinements and mean-field theory calculations to construct an effective Hamiltonian which accounts for the magnetic scattering. The interactions we identify describe an emergent spin structure which mimics the triangular lattice antiferromagnet, one of the canonical models of frustrated magnetism. © 2013, American Physical Society.
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    β-Mn: emergent simplicity in a complex structure
    (Cornell University, 2013-02-04) Paddison, JAM; Stewart, JR; Manuel, P; Courtois, P; McIntyre, GJ; Rainford, BD; Goodwin, AL
    We investigate low-temperature spin correlations in the metallic frustrated magnet β-MnCo. Single-crystal polarised-neutron scattering experiments reveal the persistence of highly-structured magnetic diffuse scattering and the absence of periodic magnetic order to T = 0.05 K. We employ reverse Monte Carlo refinements and mean-field theory simulations to construct a simple effective Hamiltonian which accounts for the magnetic scattering. The interactions we identify describe an emergent spin structure which mimics the triangular lattice antiferromagnet. The observation of a simple collective magnetic state in a complicated crystal structure is surprising because it reverses the established paradigm of elaborate emergent states arising from many-body interactions on simple lattices. We suggest that structural complexity may provide a route to realising new states of correlated quantum matter.