Multifractal phase transitions in the non-Debye relaxation processes

2000 ◽  
Vol 62 (3) ◽  
pp. 3293-3298 ◽  
Author(s):  
Alexander Leyderman ◽  
Shi-Xian Qu
Keyword(s):  
Phase Transitions ◽  
Relaxation Processes ◽  
Debye Relaxation

scholarly journals Evaluation of memory effects at phase transitions and during relaxation processes

2021 ◽  
Vol 103 (2) ◽  
Author(s):  
Hugues Meyer ◽  
Fabian Glatzel ◽  
Wilkin Wöhler ◽  
Tanja Schilling
Keyword(s):  
Phase Transitions ◽  
Memory Effects ◽  
Relaxation Processes

DYNAMICS OF THE LOW TEMPERATURE GLASS-LIKE PHASE IN MANGANITES

2003 ◽  
Vol 17 (04n06) ◽  
pp. 842-847
Author(s):  
C. CASTELLANO ◽  
F. CORDERO ◽  
R. CANTELLI ◽  
M. FERRETTI
Keyword(s):  
Distribution Function ◽  
Phase Transitions ◽  
Quantitative Analysis ◽  
Low Temperature ◽  
Imaginary Part ◽  
Lattice Relaxation ◽  
Relaxation Processes ◽  
Temperature Dependent ◽  
Energy Barriers ◽  
Nanostructured State

We report anelastic spectroscopy measurements of La 1-x Ca x MnO 3 performed in order to better characterize the nature of the phase transitions and microscopic lattice relaxation processes present in these materials. A peak in the imaginary part of the elastic susceptibility presents a behaviour typical of inhomogeneous and glass-like systems. We have performed a quantitative analysis calculating the temperature dependent distribution function of the energy barriers of the fluctuations characterizing this nanostructured state.

Release of Tetrahydrofuran, Structural Phase Transitions and Dynamic Relaxation Processes in Ca (BH4)2

2012 ◽  
Vol 184 ◽  
pp. 24-32 ◽  
Author(s):  
Annalisa Paolone ◽  
O. Palumbo ◽  
P. Rispoli ◽  
Rosario Cantelli ◽  
E. Rönnebro ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Room Temperature ◽  
Structural Phase ◽  
Young Modulus ◽  
Relaxation Processes ◽  
Structural Phase Transitions ◽  
Exponential Factor ◽  
Β Phase ◽  
Α Phase ◽  
Calcium Borohydride

Various calcium borohydride samples were investigated by means of combined measurements of thermogravimetry and mass spectrometry, and anelastic spectroscopy. On heating, the release of 2-5% tetrahydrofuran (THF) is detected in all the samples at temperatures below ~480 K, even in those which were previously thermally treated, according to procedures known from the literature, in order to remove the solvent. Dehydrogenation takes place above 480 K. Above room temperature the temperature dependence of the Young modulus of Ca (BH4)2clearly monitors the release of THF and two irreversible structural phase transitions: from the α to the α’ phase around 460 K and from the α’ to the β phase, nearly completely evolved around 590 K. Moreover, the coefficient of elastic energy dissipation presents two dynamic processes below room temperature; a peak around 120 K characterized by an activation energy of 0.20 eV and a pre-exponential factor typical of atom-cluster relaxations, that we attributed to the dynamics of THF molecules retained in the borohydride lattice, and a peak around 200 K, possibly due to the relaxation of H vacancies.

scholarly journals Диэлектрическая релаксация в тонких слоях стеклообразной системы Ge-=SUB=-28.5-=/SUB=-Рb-=SUB=-15-=/SUB=-S-=SUB=-56.5-=/SUB=-

2018 ◽  
Vol 52 (8) ◽  
pp. 912
Author(s):  
Р.А. Кастро ◽  
Н.И. Анисимова ◽  
А.А. Кононов
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
Structural Parameters ◽  
Glass Structure ◽  
Relaxation Processes ◽  
Glassy System ◽  
Debye Relaxation ◽  
Molecular Dipole ◽  
Cole Model ◽  
Charged Defects

AbstractThe results of studying dielectric relaxation processes in the Ge_28.5Pb_15S_56.5 glassy system are presented. The existence of the non-Debye relaxation process caused by the distribution of relaxors over the relaxation time according to the Cole–Cole model is revealed. The energy and structural parameters are calculated: the activation energy E _ p = 0.40 eV and the molecular dipole moment μ = 1.08 D. The detected features are explained within the model according to which the chalcogenide-glass structure is a set of dipoles formed by charged defects such as D ^+ and D ^–.

Magnetoelastic Waves in Ferromagnets in the Vicinity of Lattice Structural Phase Transitions

2018 ◽  
Vol 63 (9) ◽  
pp. 836 ◽  
Author(s):  
V. G. Bar’yakhtar ◽  
A. G. Danilevich
Keyword(s):  
Phase Transitions ◽  
Structural Phase ◽  
Martensitic Phase ◽  
Spin Reorientation ◽  
Dissipative Function ◽  
Relaxation Processes ◽  
Magnetoelastic Interaction ◽  
Degenerate Ground State ◽  
Martensitic Phase Transformations ◽  
Magnetoelastic Waves

The dispersion laws for coupled magnetoelastic waves in ferromagnets with uniaxial or cubic symmetry have been calculated. The features of obtained dispersion laws in the vicinity of spin-reorientation phase transitions are analyzed. The interaction between elastic and spin waves is shown to depend on the direction of the ferromagnet magnetic moment. The influence of the magnetoelastic interaction on the dispersion law of quasispin waves in the degenerate ground state of a uniaxial “easy plane” ferromagnet is studied. The results of calculations show that the magnetoelastic interaction eliminates the degeneration and leads to the appearance of a magnetoacoustic gap in the ferromagnet spectrum. The behavior of the spectra of coupled magnetoelastic waves in the vicinity of lattice phase transitions, namely, in the vicinity of martensitic phase transformations in materials with the shape memory effect, is analyzed. The obtained results are used to interpret experimental data obtained for the Ni–Mn–Ga alloy. The phenomenon of a drastic decrease of the elastic moduli for this alloy, when approaching the martensitic phase transition point is explained theoretically. It is shown that the inhomogeneous magnetostriction is the main factor affecting the elastic characteristics of the material concerned. A model dissipative function describing the relaxation processes associated with a damping of coupled magnetoelastic waves in ferromagnets with cubic or uniaxial symmetry is developed. It takes the symmetry of a ferromagnet into account and describes both the exchange and relativistic interactions in the crystal.

Near-Debye relaxation processes in La1−xSrxMnO3

2001 ◽  
Vol 13 (19) ◽  
pp. 4359-4366
Author(s):  
Z C Xia ◽  
C Q Tang ◽  
D X Zhou
Keyword(s):  
Relaxation Processes ◽  
Debye Relaxation

scholarly journals Preparation of SiO2-MnFe2O4 Composites via One-Pot Hydrothermal Synthesis Method and Microwave Absorption Investigation in S-Band

Molecules ◽  
2019 ◽  
Vol 24 (14) ◽  
pp. 2605 ◽  
Author(s):  
Yin ◽  
Zhang ◽  
Wang ◽  
Feng ◽  
Zhao ◽  
...  
Keyword(s):  
Hydrothermal Synthesis ◽  
Microwave Absorption ◽  
Impedance Matching ◽  
Synthesis Method ◽  
Phase Identification ◽  
Relaxation Processes ◽  
Potential Candidate ◽  
One Pot ◽  
Debye Relaxation ◽  
Attenuation Characteristic

MnFe2O4 NPs are successfully decorated on the surface of SiO2 sheets to form the SiO2-MnFe2O4 composite via one-pot hydrothermal synthesis method. The phase identification, morphology, crystal structure, distribution of elements, and microwave absorbing properties in S-band (1.55~3.4 GHz) of the as-prepared composite were investigated by XRD, SEM, TEM, and Vector Network Analyzer (VNA) respectively. Compared with the pure MnFe2O4 NPs, the as-prepared SiO2-MnFe2O4 composite exhibits enhanced microwave absorption performance in this frequency band due to the strong eddy current loss, better impedance matching, excellent attenuation characteristic, and multiple Debye relaxation processes. The maximum reflection loss of −14.87 dB at 2.25 GHz with a broader −10 dB bandwidth over the frequency range of 1.67~2.9 GHz (1.23 GHz) can be obtained at the thickness of 4 mm. Most importantly, the preparation method used here is relatively simple, hence such composite can be served as a potential candidate for effective microwave absorption in S-band.

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