Browsing by Author "Prabhakaran, D"

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    Development of the magnetic excitations of charge-stripe ordered La2-x Sr (x) NiO4 on doping towards checkerboard charge order
    (Springer, 2013-05-01) Freeman, PG; Giblin, SR; Hradil, K; Mole, RA; Prabhakaran, D
    The magnetic excitation spectrums of charge stripe ordered La2-x Sr (x) NiO4 x = 0.45 and x = 0.4 were studied by inelastic neutron scattering. We found the magnetic excitation spectrum of x = 0.45 from the ordered Ni2+ S = 1 spins to match that of checkerboard charge ordered La1.5Sr0.5NiO4. The distinctive asymmetry in the magnetic excitations above 40meV was observed for both doping levels, but an additional ferromagnetic mode was observed in x = 0.45 and not in the x = 0.4. We discuss the origin of crossover in the excitation spectrum between x = 0.45 and x = 0.4 with respect to discommensurations in the charge stripe structure. © 2013, Springer.
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    Magnetic excitations of the charge stripe electrons below half doping in La2−xSrxNiO4 (x = 0.45, 0.4)
    (American Physical Society, 2017-02-03) Freeman, PG; Giblin, SR; Hradil, K; Mole, RA; Cermak, P; Prabhakaran, D
    The low energy magnetic excitation spectrum of charge stripe ordered La2-xSrxNiO4, x=0.4 and x=0.45 samples, were studied by neutron scattering. Two excitation modes are observed in both materials, one from the ordered magnetic moments, and a second mode consistent with pseudo-one-dimensional antiferromagnetic excitations of the charge stripe electrons (q-1D). The dispersion of the q-1D excitation follows the same relation as in x=1/3 composition, with even spectral weight in the two counterpropagating branches of the x=0.4 sample, however in the x=0.45 sample only one dispersion branch has any measurable spectral weight. The evolution of the q-1D excitations on doping to the checkerboard charge ordered phase is discussed. ©2017 American Physical Society.
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    Wave vector difference of magnetic Bragg reflections and low energy magnetic excitations in charge-stripe ordered La2NiO4.11
    (Springer Nature, 2019-10-08) Freeman, PG; Giblin, SR; Skoulatos, M; Mole, RA; Prabhakaran, D
    We report on the magnetism of charge-stripe ordered La2NiO4.11±0.01 by neutron scattering and μSR. On going towards zero energy transfer there is an observed wave vector offset in the centring of the magnetic excitations and magnetic Bragg reflections, meaning the excitations cannot be described as Goldstone modes of the magnetic order. Weak transverse field μSR measurements determine the magnetically order volume fraction is 87% from the two stripe twins, and the temperature evolution of the magnetic excitations is consistent with the low energy excitations coming from the magnetically ordered volume of the material. We will discuss how these results contrast with the proposed origin of a similar wave vector offset recently observed in a La-based cuprate, and possible origins of this effect in La2NiO4.11. © 2024 The Authors - Open Access This article is licensed under a Creative Commons Attribution 4.0.