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Subject: Lanthanum alloys ×

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    Field-Angle-Resolved Magnetic Excitations as a Probe of Hidden-Order Symmetry in CeB6
    (College Park, Md. : APS, 2020) Portnichenko, P.Y.; Akbari, A.; Nikitin, S.E.; Cameron, A.S.; Dukhnenko, A.V.; Filipov, V.B.; Shitsevalova, N.Yu.; Čermák, P.; Radelytskyi, I.; Schneidewind, A.; Ollivier, J.; Podlesnyak, A.; Huesges, Z.; Xu, J.; Ivanov, A.; Sidis, Y.; Petit, S.; Mignot, J.-M.; Thalmeier, P.; Inosov, D.S.
    In contrast to magnetic order formed by electrons' dipolar moments, ordering phenomena associated with higher-order multipoles (quadrupoles, octupoles, etc.) are more difficult to characterize because of the limited choice of experimental probes that can distinguish different multipolar moments. The heavy-fermion compound CeB6 and its La-diluted alloys are among the best-studied realizations of the long-range-ordered multipolar phases, often referred to as "hidden order."Previously, the hidden order in phase II was identified as primary antiferroquadrupolar and field-induced octupolar order. Here, we present a combined experimental and theoretical investigation of collective excitations in phase II of CeB6. Inelastic neutron scattering (INS) in fields up to 16.5 T reveals a new high-energy mode above 14 T in addition to the low-energy magnetic excitations. The experimental dependence of their energy on the magnitude and angle of the applied magnetic field is compared to the results of a multipolar interaction model. The magnetic excitation spectrum in a rotating field is calculated within a localized approach using the pseudospin representation for the Γ8 states. We show that the rotating-field technique at fixed momentum can complement conventional INS measurements of the dispersion at a constant field and holds great promise for identifying the symmetry of multipolar order parameters and the details of intermultipolar interactions that stabilize hidden-order phases. © 2020 authors. Published by the American Physical Society.
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    Rejuvenation through plastic deformation of a La-based metallic glass measured by fast-scanning calorimetry
    (Amsterdam : Elsevier B.V., 2020) Meylan, C.M.; Orava, J.; Greer, A.L.
    We explore the glassy states achievable after a metallic glass is formed on liquid quenching. Samples of La55Al25Ni20 (at.%) metallic glass (rod and ribbon) are studied. The extent of structural relaxation at room temperature is characterized for this low-glass-transition temperature glass. Plastic deformation (uniaxial compression) rejuvenates the glass to states of higher enthalpy characteristic of glass formation at high cooling rate. Deformation increases the heterogeneity of the glass, widening the spectrum of relaxation times. The extent of rejuvenation in samples of low aspect ratio is compared with that under conditions of high constraint in notched samples. The deformation-induced rejuvenation is particularly susceptible to reduction on subsequent ageing. Fast-scanning calorimetry is useful in characterizing the dynamics of structural relaxation. The shadow glass transition is more evident on fast heating, and is observed in this glass for the first time. A new excess exothermic effect is observed before the glass transition.