Magnetization and Magnetocaloric Effect in Antiferromagnets with Competing Ising Exchange and Single-Ion Anisotropies

2020 ◽  
Vol 65 (10) ◽  
pp. 858
Author(s):  
V. M. Kalita ◽  
G. Yu. Lavanov ◽  
V. M. Loktev
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Field Dependence ◽  
The Other ◽  
Antiferromagnetic State ◽  
Two Phase ◽  
Ising Antiferromagnet ◽  
The Magnetic Field ◽  
System Entropy ◽  
Isostructural Phase Transition

The magnetization of a two-sublattice Ising antiferromagnet with easy-plane single-ion anisotropy, which is accompanied by two phase transitions, has been studied. The both phase transitions are induced by the magnetic field. One of them is isostructural, i.e., the system symmetry remains unchanged and a transition between two antiferromagnetic states with different sublattice magnetizations takes place. The other phase transition occurs when the antiferromagnetic state transforms into the ferromagnetic one. At both phase transitions, the field dependence of the system entropy has two successive positive jumps, which is not typical of ordinary antiferromagnets. On the other hand, if the temperature of the system is higher than the tricritical temperature of the isostructural phase transition, there appears a continuous maximum in the field dependence of the entropy.

Phase transitions of (1−x) PbZrO3 + x (Na1/2Bi1/2)TiO3 (0.01 ≤ x ≤ 0.15) solid solutions

1999 ◽  
Vol 14 (1) ◽  
pp. 83-89 ◽  
Author(s):  
Jung-Kun Lee ◽  
Hyuk-Joon Youn ◽  
Kug Sun Hong
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Solid Solutions ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
Phase Transition Temperatures ◽  
Temperature Phase Transition ◽  
Increasing Temperature

Morphotropic phase boundaries and temperature dependent phase transitions of (1 – x) PbZrO3 + x (Na1/2Bi1/2)TiO3 (0.01 ≤ x ≤ 0.15) solid solutions were investigated by x-ray diffraction, differential scanning calorimetry (DSC), and dielectric property analysis. Two morphotropic phase transitions at room temperature were found at x = 0.1 and 0.13, which were from antiferroelectric orthorhombic (with 4 × 4 × 2 superlattice [orthorhombic (I)]) to antiferroelectric orthorhombic (with 2 × 2 × 2 superlattice [orthorhombic (II)]) and from orthorhombic (II) to ferroelectric rhombohedral, respectively. With increasing temperature, the samples with 0.01 ≤ x < 0.1 showed two phase transitions, i.e., from orthorhombic (I) to orthorhombic (II) and from orthorhombic (II) to cubic. The other samples had only one phase transition with increasing temperature. Phase transition temperatures of all the samples were measured using DSC, and a phase diagram for the solid solutions was constructed. A model illustrating the antiparallel shift of Pb ions in the orthorhombic (II) phase was also proposed.

SPECTRAL PROPERTIES AND SYMMETRIES OF DOUBLE COVERINGS OF GRAPHS WITH APPLICATIONS TO SUPERCONDUCTIVITY

2005 ◽  
Vol 15 (02) ◽  
pp. 301-324
Author(s):  
JACOB RUBINSTEIN ◽  
MICHELLE SCHATZMAN
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Phase Transitions ◽  
Ground State ◽  
Spectral Properties ◽  
Embedded Graph ◽  
Symmetry Constraints ◽  
The Laplace Operator ◽  
The Magnetic Field ◽  
Double Coverings

Let M be a planar embedded graph, and let [Formula: see text] be its double covering. We count the multiplicity of the ground states of the Laplace operator on [Formula: see text] under certain symmetry constraints. The examples of interest for us are ladder-like graphs made out of n, identical rectangles. We find that in the case of an odd n, the multiplicity of the ground state is 2, and if n, is even, the ground state is simple. This result gives an answer to a conjecture by Parks on the type of phase transitions that can occur in a superconducting ladder: Parks conjectured that in the case when the magnetic field is one half fluxoid per rectangle, the phase transition would be continuous in the case of a ladder made out of two rectangles. Our result indeed implies Parks conjecture and generalizes it to any even ladder. The mathematics of this paper is a mixture of topology, symmetry arguments and comparison theorem between the eigenvalues of Laplace operators on graphs with well chosen boundary conditions.

scholarly journals Проявление структурных фазовых переходов в кристалле Rb-=SUB=-2-=/SUB=-KLuF-=SUB=-6-=/SUB=- в спектрах комбинационного рассеяния света

2019 ◽  
Vol 126 (4) ◽  
pp. 423
Author(s):  
А.С. Крылов ◽  
А.Н. Втюрин ◽  
В.Н. Воронов ◽  
С.Н. Крылова
Keyword(s):  
Phase Transitions ◽  
Monoclinic Phase ◽  
Tricritical Point ◽  
Structural Phase ◽  
Double Perovskite ◽  
Spectral Lines ◽  
The Other ◽  
Structural Phase Transitions ◽  
Two Phase ◽  
Temperature Dependences

AbstractThe Raman spectra of an Rb_2KLuF_6 crystal are studied in the temperature range from 8 to 375 K, which includes two phase transitions: one of which proceeds from a cubic to a tetragonal phase, while the other transition takes place from a tetragonal to a monoclinic phase. An analysis of the temperature dependences of parameters of spectral lines shows that the former transition is of the second kind, while the latter transition is of the first kind, close to the tricritical point. It is shown that the structural phase transitions in the Rb_2KLuF_6 double perovskite are not associated with disordering. The former transition is associated with rotations of LuF_6 octahedra around the fourth-order axis, while the latter transition is related with rotations of octahedra and displacements of rubidium ions.

scholarly journals Chiral phase transition in QED3 at finite temperature

2016 ◽  
Vol 31 (36) ◽  
pp. 1650198
Author(s):  
Pei-Lin Yin ◽  
Hai-Xiao Xiao ◽  
Wei Wei ◽  
Hong-Tao Feng ◽  
Hong-Shi Zong
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Critical Temperature ◽  
Finite Temperature ◽  
Chiral Symmetry Breaking ◽  
Chiral Condensate ◽  
The Other ◽  
Thermodynamic Quantities ◽  
Chiral Phase ◽  
Chiral Phase Transition

In the framework of Dyson–Schwinger equations, we employ two kinds of criteria (one kind is the chiral condensate, the other kind is thermodynamic quantities, such as the pressure, the entropy, and the specific heat) to investigate the nature of chiral phase transitions in QED3 for different fermion flavors. It is found that the chiral phase transitions in QED3 for different fermion flavors are all typical second-order phase transitions; the critical temperature and order of the chiral phase transition obtained from the chiral condensate and susceptibility are the same with that obtained by the thermodynamic quantities, which means that they are equivalent in describing the chiral phase transition; the critical temperature decreases as the number of fermion flavors increases and there is a boundary that separates the [Formula: see text] plane into chiral symmetry breaking and restoration regions.

Investigation of the Phase Transition at 67.17 K in the Thiourea-CCl4 Inclusion Compound. As Studied by 14N NQR

1994 ◽  
Vol 49 (1-2) ◽  
pp. 433-438 ◽  
Author(s):  
J. El Ghallali ◽  
M. Gourdji ◽  
L. Guibé ◽  
A. Péneau
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Carbon Tetrachloride ◽  
Inclusion Compound ◽  
Central Line ◽  
Host Lattice ◽  
Central Component ◽  
Two Phase ◽  
Temperature Range ◽  
Calorimetric Measurements

Abstract The 14N NQR from the host lattice of the thiourea-carbon tetrachloride inclusion compound. From calorimetric measurements, two phase transitions are known to occur at 67.2 K and 41.3 K in this compound. Above the 67.2 K transition, the 14N NQR spectrum consists of one resonance, though a small splitting of about 0.5 kHz is seen at temperatures up to ca. 105 K. Below the transition, the resonance appears as a central component, in continuation of the resonance above the transition, and two satellites at + 10 kHz and -8 kHz from the central line. The transition from the single resonance to a fully resolved spectrum takes place in a temperature range of less than one kelvin. The results are compared with those previously obtained with the thiourea-cyclohexane inclusion compound.

The Theoretical Study of the Cinnabar-to-Rocksalt Phase Transitions of HgTe and CdTe under High Pressure

2014 ◽  
Vol 1004-1005 ◽  
pp. 1608-1614 ◽  
Author(s):  
Xi Duo Hu ◽  
De Hai Zhu ◽  
Zhi Feng Zeng ◽  
Shao Rui Sun
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Phase Transitions ◽  
Theoretical Study ◽  
Chain Structure ◽  
Two Phase ◽  
Principle Calculation ◽  
First Principle Calculation ◽  
First Order ◽  
Rocksalt Phase

We performed the first-principle calculation to study the structures of cinnabar phase and the Cinnabar-to-rocksalt Phase transitions of HgTe and CdTe under high pressure. The calculated results show that for HgTe, the zincblende-to-cinnabar phase transition is under 2.2GPa, and the cinnabar-to-rocksalt phase transition is under 5.5 GPa; For CdTe, the two phase transitions occur under 4.0 GPa and 4.9 GPa, respectively, which well agree with the experimental results. The cinnabar-to-rocksalt phase transitions of most compounds, including HgTe and CdTe, except HgS are of first-order, and it is due to that their cinnabar phases are not chain structure as HgS and there are no relaxation process before the phase transition.

scholarly journals A study of the phase transition behavior of mixed ammonium sulfate – malonic acid aerosols

2004 ◽  
Vol 4 (3) ◽  
pp. 2949-2971 ◽  
Author(s):  
C. F. Braban ◽  
J. P. D. Abbatt
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Relative Humidity ◽  
Ammonium Sulfate ◽  
Malonic Acid ◽  
Binary Systems ◽  
Dry Mass ◽  
The Other ◽  
Phase Transition Behavior ◽  
Infrared Extinction

Abstract. This is a study into the phase transitions of aerosol composed of the ternary system ammonium sulfate (AS) – malonic acid (MA) – water using infrared extinction spectroscopy. Twelve compositions were studied in both deliquescence and efflorescence mode experiments. The presence of a MA fraction, by dry mass, (fMA) of 0.1 in an AS aerosol altered the relative humidity at which the phase transitions occur in an atmospherically significant manner. For compositions with 0.25<fMA<0.90, no distinct "deliquescence" was observed, contrary to the observed behavior in the binary systems. The crystallization of both the MA and AS components is suppressed by the presence of the other component in the aerosol. At fMA=0.9, the crystallization relative humidity of MA was lowered from RH=6% to less than 1%. Similarly, at fMA=0.4, the AS component did not crystallize. The atmospheric implications of the results are discussed.

scholarly journals Особенности влияния состава и кристаллической структуры на поведение электрофизических свойств сплавов системы Ni-=SUB=-(1-x)-=/SUB=-W-=SUB=-x-=/SUB=- при низких температурах

2018 ◽  
Vol 60 (10) ◽  
pp. 1888
Author(s):  
В.В. Деревянко ◽  
М.С. Сунгуров ◽  
Т.В. Сухарeва ◽  
В.А. Финкель ◽  
Ю.Н. Шахов
Keyword(s):  
Phase Transition ◽  
The Other ◽  
Two Phase ◽  
Magnetic Structures ◽  
Concentration Dependences ◽  
Temperature Dependences ◽  
Chemical And Phase Compositions ◽  
The One ◽  
Percolation Processes ◽  
Bcc Phase

AbstractThe problem of establishing the correlation between, on the one hand, the chemical and phase compositions of Ni_1– x W_ x alloys (0 ≤ x ≤ 0.5) and, on the other hand, the character of the temperature dependences of the electrical resistivity, is considered. Based on the experimental ρ( T ) curves, the concentration dependences of are reconstructed in the wide temperature range (50 K ≤ T ≤ 273 K). The ρ( x ) curves have features related to a change in the crystal structures of the alloys (concentration fcc–bcc phase transition), their magnetic structures and percolation processes occurring in the two-phase fcc + bcc medium.

Synthesis, characterization and phase transitions in the inorganic–organic layered perovskite-type hybrids [(C n H2n + 1NH3)2PbI4], n = 4, 5 and 6

2007 ◽  
Vol 63 (5) ◽  
pp. 735-747 ◽  
Author(s):  
David G. Billing ◽  
Andreas Lemmerer
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Layered Perovskite ◽  
Temperature Phase ◽  
Two Phase ◽  
Structural Details ◽  
Temperature Phase Transition ◽  
Higher Temperature ◽  
First Order Phase ◽  
Perovskite Type

Three inorganic–organic layered perovskite-type hybrids of the general formula [(C n H2n + 1NH3)2PbI4], n = 4, 5 and 6, display a number of reversible first-order phase transitions in the temperature range from 256 to 393 K. [(C4H9NH3)2PbI4] has a single phase transition, [(C5H11NH3)2PbI4] has two phase transitions and [(C6H13NH3)2PbI4] has three phase transitions. In all three cases, the lowest-temperature phase transition is thermochromic and the crystals change colour from yellow in their lowest-temperature phase to orange in their higher-temperature phase for [(C4H9NH3)2PbI4] and [(C6H13NH3)2PbI4], and from orange to red for [(C5H11NH3)2PbI4]. The structural details associated with this phase transition have been investigated via single-crystal X-ray diffraction, SC-XRD, for all three compounds.

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