Structural and Magnetic Phase Transitions in ErFe2Hx Hydrides

2009 ◽  
Vol 152-153 ◽  
pp. 33-36 ◽  
Author(s):  
L.A. Shreder ◽  
V.S. Gaviko ◽  
N.V. Mushnikov ◽  
P.B. Terent’ev
Keyword(s):  
Phase Transition ◽  
Hydrogen Content ◽  
Magnetic Moments ◽  
Exchange Interactions ◽  
Rhombohedral Phase ◽  
Small Variation ◽  
Intermediate Stage ◽  
Magnetic Phase Transitions ◽  
Magnetic Studies ◽  
The Difference

Temperature dependences of the lattice parameters, magnetization and magnetic susceptibility have been measured for the ErFe2Hx hydrides with different hydrogen content x and for the ErFe2D3.1 deuteride. For the samples with a hydrogen content of about 3.1, structural transition from the cubic to the rhombohedral phase has been observed in the temperature range 280 – 310 K. Small variation of hydrogen content does not shift the transition temperature, but influences the amount of the low-temperature rhombohedral phase. The temperature dependence of magnetization shows up an anomaly in the range of the phase transition, which is due to the difference in the magnitudes of magnetic moments and exchange interactions in two phases. Structural and magnetic studies point to a diffusion nature of the phase transition. Upon heating the samples in vacuum there takes place decomposition of the hydride. The hydride with x = 1.6 which forms at the intermediate stage of decomposition possesses an ordering temperature higher than that for the parent ErFe2 compound.

Peculiarities of Elastic Properties of RE Cobaltites RBaCo4O7 (R = Dy - Er, Y) at Magnetic Phase Transitions

2015 ◽  
Vol 233-234 ◽  
pp. 145-148 ◽  
Author(s):  
Zoya Kazei ◽  
Vyacheslav Snegirev ◽  
Alexander Andreenko ◽  
Ludmila Kozeeva ◽  
Margarita Kameneva
Keyword(s):  
Phase Transition ◽  
Rare Earth ◽  
Young’S Modulus ◽  
Magnetic Phase Transition ◽  
Magnetic Phase ◽  
Young's Modulus ◽  
Exchange Interactions ◽  
Magnetic Phase Transitions ◽  
Wide Range ◽  
Irreversible Effects

It has been found that the temperature dependences of the Young’s modulus for rare-earth cobaltites RBaCo4O7 (R = Dy - Er, Y) exhibit significant hysteresis and irreversible effects over a wide range (80–280) K between the structural and magnetic phase transition temperatures. At the magnetic phase transition temperature, there are weak and smoothed anomalies of the Young’s modulus, which correlate with the low dimensionality and frustration of the exchange interactions in the Kagome lattice of the Co subsystem for the studied rare-earth cobaltites.

Magnetic Phase Transitions in the Two-Dimensional Random Mixture K2CuxCo1-xF4with Competing Exchange Interactions

1990 ◽  
Vol 59 (5) ◽  
pp. 1792-1800 ◽  
Author(s):  
Masayuki Itoh ◽  
Isao Yamada ◽  
Mamoru Ishizuka ◽  
Kiichi Amaya ◽  
Tatsuo Kobayashi ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Magnetic Phase ◽  
Exchange Interactions ◽  
Magnetic Phase Transitions ◽  
Two Dimensional ◽  
Random Mixture

LONG‐TIME RESPONSE PREDICTED BY EXACT ELASTIC RAY THEORY

Geophysics ◽  
1965 ◽  
Vol 30 (3) ◽  
pp. 363-368 ◽  
Author(s):  
T. W. Spencer
Keyword(s):  
Formal Solution ◽  
Intermediate Stage ◽  
Time Limit ◽  
Time Interval ◽  
Individual Response ◽  
Axially Symmetric ◽  
Long Time ◽  
The Difference ◽  
The Individual ◽  
Significant Figures

The formal solution for an axially symmetric radiation field in a multilayered, elastic system can be expanded in an infinite series. Each term in the series is associated with a particular raypath. It is shown that in the long‐time limit the individual response functions produced by a step input in particle velocity are given by polynomials in odd powers of the time. For rays which suffer m reflections, the degree of the polynomials is 2m+1. The total response is obtained by summing all rays which contribute in a specified time interval. When the rays are selected indiscriminately, the difference between the magnitude of the partial sum at an intermediate stage of computation and the magnitude of the correct total sum may be greater than the number of significant figures carried by the computer. A prescription is stated for arranging the rays into groups. Each group response function varies linearly in the long‐time limit and goes to zero when convolved with a physically realizable source function.

Second hyperpolarizability of multimetallocenes [Cp–Mn–Cp] of Be, Mg and Ca

2015 ◽  
Vol 14 (01) ◽  
pp. 1550002 ◽  
Author(s):  
Kaushik Hatua ◽  
Prasanta K. Nandi
Keyword(s):  
Charge Transfer ◽  
Theoretical Study ◽  
Small Variation ◽  
Cooperative Effect ◽  
Second Hyperpolarizability ◽  
Nlo Property ◽  
Metal Atoms ◽  
Bonding Interaction ◽  
Charge Transfer Transitions ◽  
The Difference

Multimetallocene complexes ( Cp – M n– Cp ) of Be , Mg and Ca have been considered for the theoretical study of static second hyperpolarizability using a number of DFT functionals. Owing to the cooperative effect in bonding, beryllium forms multiberyllocene complexes ( Cp – Be n– Cp ) which have sufficient thermal stability with respect to dissociation into neutral fragments up to n = 10. On the other hand, multimetallocene complexes of Mg and Ca are found to be stable for n ≤ 5 which may be due to the weaker covalent bonding interaction between the larger metal atoms. The rather small variation of linear and cubic polarizabilities of Cp – Be n– Cp complexes beyond n = 5 arises from the rather weaker charge transfer transitions. The difference in NLO property among the investigated metal complexes arises from the extent of charge transfer from the terminal metal atoms and the distance between them. The charge transfer at longer distances in the ground state of Mg and Ca complexes leads to more intense electronic transition — the spectroscopic parameters of which strongly favors the enhancement of second hyperpolarizability.

Studies on proper time regularization and the QCD chiral phase transition

2019 ◽  
Vol 34 (01) ◽  
pp. 1950003
Author(s):  
Yu-Qiang Cui ◽  
Zhong-Liang Pan
Keyword(s):  
Phase Transition ◽  
Small Parameter ◽  
Effective Mass ◽  
Finite Temperature ◽  
Chemical Potential ◽  
Proper Time ◽  
Chiral Phase ◽  
Chiral Phase Transition ◽  
Njl Model ◽  
The Difference

We investigate the finite-temperature and zero quark chemical potential QCD chiral phase transition of strongly interacting matter within the two-flavor Nambu–Jona-Lasinio (NJL) model as well as the proper time regularization. We use two different regularization processes, as discussed in Refs. 36 and 37, separately, to discuss how the effective mass M varies with the temperature T. Based on the calculation, we find that the M of both regularization schemes decreases when T increases. However, for three different parameter sets, quite different behaviors will show up. The results obtained by the method in Ref. 36 are very close to each other, but those in Ref. 37 are getting farther and farther from each other. This means that although the method in Ref. 37 seems physically more reasonable, it loses the advantage in Ref. 36 of a small parameter dependence. In addition, we also, find that two regularization schemes provide similar results when T [Formula: see text] 100 MeV, while when T is larger than 100 MeV, the difference becomes obvious: the M calculated by the method in Ref. 36 decreases more rapidly than that in Ref. 37.

scholarly journals Magnetic Transitions in the Co-Modified Mn2Sb System

Inorganics ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 113 ◽  
Author(s):  
Johanna Wilden ◽  
Andreas Hoser ◽  
Mamuka Chikovani ◽  
Jörg Perßon ◽  
Jörg Voigt ◽  
...  
Keyword(s):  
Phase Transition ◽  
Magnetic Moments ◽  
Induction Melting ◽  
Magnetic Structures ◽  
Co Substitution ◽  
First Order Phase Transition ◽  
Phase Transition Temperatures ◽  
Underlying Mechanisms ◽  
The Individual ◽  
First Order Phase

Mn2Sb is ferrimagnetic below its Curie temperature (TC) and passes through a spin flip transition with decreasing temperature. The Co substitution induces an additional first-order phase transition from the ferrimagnetic (FRI) to an antiferromagnetic (AFM) state. This phase transition is connected to a sizable magnetocaloric effect (MCE). To understand the underlying mechanisms, the temperature dependence of structural and magnetic changes was analyzed. At the same time, the influence of the Co substitution was explored. Three Mn2−xCoxSb (x = 0.1, 0.15, 0.2) compounds were synthesized by cold crucible induction melting. Neutron powder diffraction was performed to determine the magnetic structures and to obtain the individual magnetic moments on both symmetrically independent Mn sites. In combination with the temperature-dependent magnetization measurements, the magnetic phase transition temperatures were identified. In the low-temperature range, additional antiferromagnetic peaks were detected, which could be indexed with a propagation vector of (0 0 ½). In Mn1.9Co0.1Sb at 50 K and in Mn1.8Co0.2Sb at 200 K, a co-existence of the FRI and the AFM state was observed. The pure AFM state only occurs in Mn1.8Co0.2Sb at 50 K.

Crystallographic preferred orientation in wüstite (FeO) through the cubic-to-rhombohedral phase transition

2012 ◽  
Vol 39 (8) ◽  
pp. 613-626 ◽  
Author(s):  
P. Kaercher ◽  
S. Speziale ◽  
L. Miyagi ◽  
W. Kanitpanyacharoen ◽  
H.-R. Wenk
Keyword(s):  
Phase Transition ◽  
Rhombohedral Phase ◽  
Preferred Orientation ◽  
Crystallographic Preferred Orientation

scholarly journals Holographic Lifshitz superconductors with Weyl correction

2020 ◽  
Vol 80 (11) ◽  
Author(s):  
Jun-Wang Lu ◽  
Ya-Bo Wu ◽  
Bao-Ping Dong ◽  
Yu Zhang
Keyword(s):  
Phase Transition ◽  
Black Hole ◽  
Critical Temperature ◽  
Numerical Method ◽  
Analytical Methods ◽  
Competitive Effects ◽  
Lifshitz Black Hole ◽  
The Difference ◽  
Lower Temperature ◽  
Numerical And Analytical Methods

AbstractAt the probe approximation, we construct a holographic p-wave conductor/superconductor model in the five-dimensional Lifshitz black hole with the Weyl correction via both numerical and analytical methods, and study the effects of the Lifshitz parameter z as well as the Weyl parameter $$\gamma $$ γ on the superconductor model. As we take into account one of the two corrections separately, the increasing z ($$\gamma $$ γ ) inhibits(enhances) the superconductor phase transition. When the two corrections are considered comprehensively, they display the obviously competitive effects on both the critical temperature and the vector condensate. In particular, the promoting effects of the Weyl parameter $$\gamma $$ γ on the critical temperature are obviously suppressed by the increasing Lifshitz parameter. Meanwhile, in the case of $$z<2.35$$ z < 2.35 ($$z>2.35$$ z > 2.35 ), the condensate at lower temperature decreases(increases) with the increasing Weyl parameter $$\gamma $$ γ . What is more, the difference among the condensate with the fixed Weyl parameter($$\gamma =-\frac{6}{100},0,\frac{4}{100}$$ γ = - 6 100 , 0 , 4 100 ) decreases(increases) with the increasing Lifshitz parameter z in the region $$z<2.35$$ z < 2.35 ($$z>2.35$$ z > 2.35 ). Furthermore, the increasing z obviously suppresses the real part of conductivity for all value of the Weyl parameter $$\gamma $$ γ . In addition, the analytical results agree well with the ones from the numerical method.

Using alloying to promote the subtle rhombohedral phase transition in vanadium

2010 ◽  
Vol 22 (46) ◽  
pp. 465503
Author(s):  
Byeongchan Lee ◽  
Robert E Rudd ◽  
John E Klepeis
Keyword(s):  
Phase Transition ◽  
Rhombohedral Phase

Magnetic Phase Transitions and Magnetocaloric Effect in R2Fe17 (R = Y, Tb, Er)

2015 ◽  
Vol 233-234 ◽  
pp. 204-207 ◽  
Author(s):  
S.A. Nikitin ◽  
I.A. Ovchenkova ◽  
Georgiy A. Tskhadadze ◽  
Konstantin P. Skokov
Keyword(s):  
Transition Temperature ◽  
Magnetocaloric Effect ◽  
Magnetic Phase ◽  
Magnetic Transition ◽  
Exchange Interactions ◽  
Thermodynamic Theory ◽  
Magnetic Phase Transitions ◽  
Magnetic Transition Temperature ◽  
Local Fluctuations ◽  
Direct Measurements

The direct measurements of the magnetocaloric effect (MCE) and the magnetization for R2Fe17 (R = Y, Tb, Dy) compounds are reported. The maximal values of the MCE for different R2Fe17 compounds are almost the same at the Curie temperature and are equal to 0.8 – 0.85 K at ΛH = 13.5 kOe. The field dependencies of the magnetization and MCE and the dependence of MCE via magnetization deviates from the classical regularities and describes by the thermodynamic theory attracting the higher terms. Obviously the occurrence of the mixed exchange interactions in these compounds leads to the requirement of consideration both thermal and local fluctuations of the exchange integrals near the magnetic transition temperature.

Sign in / Sign up

Export Citation Format

Share Document