Measuring the dynamical critical exponent of an ordering alloy using x-ray photon correlation spectroscopy

Frédéric Livet (1) , Mathieu Fèvre (2) , Guillaume Beutier (1) , Federico Zontone (3) , Yuriy Chushkin (3) , Mark Sutton (4)

1 SIMaP - Science et Ingénierie des Matériaux et Procédés
2 LEM, UMR 104 CNRS-ONERA, Université Paris Saclay (COmUE) [Châtillon]
3 ESRF - European Synchrotron Radiation Facility
4 McGill University = Université McGill [Montréal, Canada]

The dynamics of the order fluctuations in the AuAgZn2 close to the critical point (Tc≃609 K) was observed by coherent x-ray scattering. With the high beam intensity of the ID10 ESRF beamline and with the new pixel detector, the dynamics was measured with a few tens of millisecond resolution. The intensity connected to the diffuse scattering corresponding to fluctuations was unambiguously distinguished from the surface pretransitional ordering occurring in this system close to Tc. The variations of the fluctuation time with temperature and wave vectors were measured in this system belonging to the universality class of Ising second order transition with a nonconserved order parameter. The direct observation of the critical slowing down in the vicinity of the second-order transition led to an estimate of the dynamic exponent z≃1.96(11), in rough agreement with theory (model “A” of Hohenberg and Halperin [Rev. Mod. Phys. 49, 435 (1977)]).

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Frédéric Livet, Mathieu Fèvre, Guillaume Beutier, Federico Zontone, Yuriy Chushkin, et al.. Measuring the dynamical critical exponent of an ordering alloy using x-ray photon correlation spectroscopy. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2018, 98 (1), ⟨10.1103/PhysRevB.98.014202⟩. ⟨hal-01844484⟩