scholarly journals Ultrafast nanoimaging of the order parameter in a structural phase transition

2021 ◽  
Vol 27 (S1) ◽  
pp. 2958-2961
Author(s):  
Thomas Danz ◽  
Till Domröse ◽  
Claus Ropers
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Order Parameter ◽  
Structural Phase

Generalized susceptibility of dislocations in ferroelectrics and ferromagnetics

1990 ◽  
Vol 193 (3-4) ◽  
Author(s):  
V. V. Dezhin ◽  
V. N. Nechaev ◽  
A. M. Roshchupkin
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Order Parameter ◽  
Transition Point ◽  
Natural Frequencies ◽  
Structural Phase ◽  
Phase Transition Point

AbstractA generalized susceptibility of dislocations is calculated in ferroelectrics and ferromagnetics and also in the vicinity of a structural phase transition point by which natural frequencies for dislocations are defined, when the fariation of the order parameter

scholarly journals Manifestation of magnetoelastic interactions in Raman spectra of HoxNd1−xFe3(BO3)4 crystals

2018 ◽  
Vol 08 (02) ◽  
pp. 1850011 ◽  
Author(s):  
A. S. Krylov ◽  
S. N. Sofronova ◽  
I. A. Gudim ◽  
S. N. Krylova ◽  
Rajesh Kumar ◽  
...  
Keyword(s):  
Phase Transition ◽  
Raman Spectra ◽  
Structural Phase Transition ◽  
Solid Solutions ◽  
Order Parameter ◽  
Soft Mode ◽  
Magnetic Phase ◽  
Structural Phase ◽  
Exchange Interactions ◽  
Magnetoelastic Interaction

Raman spectra of Ho[Formula: see text]NdxFe(BO3)4 ([Formula: see text], 0.75, 0.5, 0.25) have been studied in temperature range 10–400[Formula: see text]K. Two compositions ([Formula: see text], [Formula: see text]) demonstrate structural phase transition with soft mode restoration. The addition of Nd atoms increases interatomic spacing and decreases the temperature of structural phase transition. The solid solutions ([Formula: see text], 0.5, 0.25) demonstrate the emergence of the peaks corresponding to magnetoelastic interaction below Néel temperature. The order parameter of the magnetic phase transition has been determined. The equal concentrations of holmium and neodymium atoms prevent magnon soft modes condensation caused by exchange interactions in Fe–O–Fe chains are observed. Calculations confirm the data obtained in the experiment.

A structural phase transition in NaTaOGeO4 and its relation to phase transitions in titanite

2007 ◽  
Vol 63 (4) ◽  
pp. 545-550 ◽  
Author(s):  
Thomas Malcherek
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Transition Metal ◽  
Structural Phase Transition ◽  
Order Parameter ◽  
Diffuse Scattering ◽  
Structural Phase ◽  
Group Symmetry ◽  
Critical Temperatures ◽  
Symmetry Properties

A structural phase transition from space-group symmetry P21/c to C2/c is reported for NaTaOGeO4 (NTGO). The critical temperature has been located at T c = 116 K, based on the appearance of sharp diffraction maxima at positions h + k = 2n + 1 of reciprocal space on cooling below this temperature. Strongly anisotropic diffuse scattering in sheets normal to [001] is observable for T > T c and persists up to ambient temperature. Similarities to phase transitions observed in other compounds of the titanite structure type are discussed. The symmetry properties of these phase transitions are reassessed on the basis of the structural data available. The primary order parameter is identified with the displacement of the transition metal cation M (M = Ta in NTGO) away from the centre of symmetry that it nominally occupies in the paraphase. The order parameter transforms as the Y_{2}^{-} representation. The anisotropic diffuse scattering is attributed to the one-dimensional correlation of local M displacements parallel to the direction of chains of trans-corner-sharing MO6 octahedra. The critical temperatures of the isomorphous phase transitions in various titanite-type compounds depend linearly on the squared transition-metal displacement measured in the ordered P21/c phase.

scholarly journals Ultrafast nanoimaging of the order parameter in a structural phase transition

Science ◽  
2021 ◽  
Vol 371 (6527) ◽  
pp. 371-374 ◽  
Author(s):  
Thomas Danz ◽  
Till Domröse ◽  
Claus Ropers
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
Structural Phase Transition ◽  
Order Parameter ◽  
Structural Phase ◽  
Density Wave ◽  
Transient State ◽  
Laser Pulses ◽  
Dark Field ◽  
Ultrashort Laser Pulses

Understanding microscopic processes in materials and devices that can be switched by light requires experimental access to dynamics on nanometer length and femtosecond time scales. Here, we introduce ultrafast dark-field electron microscopy to map the order parameter across a structural phase transition. We use ultrashort laser pulses to locally excite a 1T-TaS2 (1T-polytype of tantalum disulfide) thin film and image the transient state of the specimen by ultrashort electron pulses. A tailored dark-field aperture array allows us to track the evolution of charge-density wave domains in the material with simultaneous femtosecond temporal and 5-nanometer spatial resolution, elucidating relaxation pathways and domain wall dynamics. The distinctive benefits of selective contrast enhancement will inspire future beam-shaping technology in ultrafast transmission electron microscopy.

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