scholarly journals NGHIÊN CỨU BIỂU HIỆN TỚI HẠN TRONG CÁC BĂNG HỢP KIM Fe88Co2Zr7B2Cu1

2021 ◽  
Vol 11 (4) ◽  
pp. 3
Author(s):  
Nguyen Hai Yen ◽  
Nguyen Hoang Ha ◽  
Pham Thi Thanh ◽  
Kieu Xuan Hau ◽  
Tran Dang Thanh ◽  
...  
Keyword(s):  
Phase Transition ◽  
Melt Spinning ◽  
Mean Field ◽  
Critical Parameters ◽  
Scaling Relation ◽  
X Ray Diffraction ◽  
Mean Field Model ◽  
Fisher Method ◽  
The Mean ◽  
Arrott Plots

In this work, we investigated the critical behavior of Fe88Co2Zr7B2Cu1 alloy ribbons prepared using a single-roller melt-spinning method. X-ray diffraction analysis shows that the alloy is almost amorphous. This alloy undergoes a second-order ferromagnetic-paramagnetic (FM-PM) phase transition at room temperature (Curie temperature TC = 296 K). To investigate the nature of the FM-PM phase transition near the TC for the alloy, we performed a critical-exponent study. Based on modified Arrott plots, the Kouvel-Fisher method, and Widom’s scaling relation, a set of critical parameters were determined. The critical parameters are β = 0.545 ± 0.041 and γ = 1.109 ± 0.018 obtained from the modified Arrott plots; β = 0.547 ± 0.005 and γ = 1.105 ± 0.016 from the Kouvel-Fisher method, and d = 3.035 ± 0.059 from Widom’s scaling relation. These values are close to those expected for the mean-field model, revealing long-range FM interactions.

Calculation of the tilt angle and susceptibility for the α–β transition in quartz using a mean field model

2017 ◽  
Vol 31 (09) ◽  
pp. 1750092 ◽  
Author(s):  
H. Yurtseven ◽  
U. Ipekoğlu ◽  
S. Ateş
Keyword(s):  
Experimental Data ◽  
Phase Transition ◽  
Temperature Dependence ◽  
Tilt Angle ◽  
Phenomenological Model ◽  
Order Parameter ◽  
Field Model ◽  
Mean Field ◽  
Mean Field Model ◽  
The Mean

Tilt angle (order parameter) and the susceptibility are calculated as a function of temperature for the [Formula: see text]–[Formula: see text] transition in quartz using a Landau phenomenological model. The tilt angle as obtained from the model is fitted to the experimental data from the literature and the temperature dependence of the tilt angle susceptibility is predicted close to the [Formula: see text]–[Formula: see text] transition in quartz. Our results show that the mean field model explains the observed behavior of the [Formula: see text]–[Formula: see text] phase transition in quartz adequately and it can be applied to some related materials.

scholarly journals Investigation of magnetic phase transition and magnetocaloric effect of (Ni,Co)-Mn-Al melt-spun ribbons

2018 ◽  
Vol 185 ◽  
pp. 05001
Author(s):  
Yen Nguyen ◽  
Mai Nguyen ◽  
Quang Vu ◽  
Thanh Pham ◽  
Victor Koledov ◽  
...  
Keyword(s):  
Phase Transition ◽  
Magnetocaloric Effect ◽  
Magnetic Phase Transition ◽  
Magnetic Phase ◽  
Mean Field ◽  
Entropy Change ◽  
Soft Magnetic Materials ◽  
Critical Parameters ◽  
Mean Field Model ◽  
Diffraction Patterns

Magnetic phase transition, magnetocaloric effect and critical parameters of Ni50-xCoxMn50-yAly (x = 5 and 10; y = 17, 18 and 19) rapidly quenched ribbons have been studied. X-ray diffraction patterns exhibit a coexistence of the L21 and 10M crystalline phases of the ribbons. Magnetization measurements show that all the samples behave as soft magnetic materials with a low coercive force less than 60 Oe. The shape of thermomagnetization curves considerably depends on Co and Al concentrations. The Curie temperature (TC) of the alloy ribbons strongly increases with increasing the Co concentration and slightly decreases with increasing the Al concentration. The Ni45Co5Mn31Al19 and Ni40Co10Mn33Al17 ribbons reveal both the positive and negative magnetocaloric effects. Under magnetic field change (ΔGH) of 13.5 kOe, the maximum magnetic entropy change (|ΔSm|max) of the Ni45Co5Mn31Al19 ribbon is about 2 and -1 J·kg−1·K−1 for negative and positive magnetocaloric effects, respectively. Basing on Arrott - Noakes and Kouvel - Fisher methods, critical parameters of the Ni45Co5Mn31Al19 ribbon were determined to be TC ≈ 290 K, β ≈ 0.58, γ ≈ 0.92 and δ ≈ 2.59. The obtained values of the critical exponents indicate that the magnetic order of the alloy ribbon is close to the mean-field model.

scholarly journals Tunable magnetocaloric effect in amorphous Gd-Fe-Co-Al-Si alloys

2022 ◽  
Author(s):  
Natalia Lindner ◽  
Zbigniew Śniadecki ◽  
Mieszko Kołodziej ◽  
Jean-Marc Grenèche ◽  
Jozef Marcin ◽  
...  
Keyword(s):  
Magnetocaloric Effect ◽  
Mean Field ◽  
Magnetic Behavior ◽  
Entropy Change ◽  
X Ray Diffraction ◽  
Mean Field Model ◽  
Melt Spun ◽  
Parent Alloy ◽  
The Mean ◽  
The Magnetic Field

AbstractA magnetocaloric effect with wide tunability was observed in melt-spun amorphous Gd65Fe15-xCo5+xAl10Si5 (x = 0, 5, 10) alloys of different Fe/Co ratios. Their magnetic properties were compared with those of the previously investigated parent alloy Gd65Fe10Co10Al15. The glassy structure of the melt-spun samples was confirmed by X-ray diffraction (XRD) and 57Fe Mössbauer spectrometry. Their Curie temperatures (TC) were between 155 and 195 K and increased significantly with decreasing Co content. The highest value of the magnetic entropy change ΔSM = − 6.8 J/kg K was obtained for Gd65Fe5Co15Al10Si5, when the magnetic field was increased from 0 to 5 T. Refrigerant capacity (RC) takes values close to 700 J/kg for the whole series of the alloys. The occurrence of the second-order phase transition and the conformity of the magnetic behavior with the mean field model were concluded on the basis of the analysis of the universal curves and the values of the exponent n (ΔSM ∝ Hn). Graphical abstract

The mean field model withP2θ2coupling for the smectic A-smectic C* phase transition in liquid crystals

1998 ◽  
Vol 66 (1-4) ◽  
pp. 259-270 ◽  
Author(s):  
S. SalihoĞLu ◽  
H. Yurtseven ◽  
A. Giz ◽  
D. Kayişoğlu ◽  
A. Konu
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Field Model ◽  
Mean Field ◽  
Mean Field Model ◽  
Smectic A ◽  
Smectic C ◽  
The Mean

scholarly journals Relativistic selfinteracting particle­-antiparticle system of bosons

2020 ◽  
Vol 28 (2) ◽  
pp. 3-18
Author(s):  
D. Anchishkin ◽  
V. Gnatovskyy ◽  
D. Zhuravel ◽  
V. Karpenko
Keyword(s):  
Phase Transition ◽  
Thermodynamic Properties ◽  
Specific Heat ◽  
Temperature Interval ◽  
Thermodynamic Functions ◽  
Field Model ◽  
Mean Field ◽  
Einstein Condensate ◽  
Mean Field Model ◽  
The Mean

Thermodynamic properties of a system of an interacting boson particles and antiparticles at high tem­peratures are studied within the framework of the thermodynamically consistent Skyrme-­like mean-­field model. The mean field contains both attractive and repulsive terms. Self­-consistency relations between the mean field and thermodynamic functions are derived. We assume a conservation of the isospin density for all temperatures. It is shown that, independently of the strength of the attractive mean field, at the critical tem­perature Tc the system undergoes the phase transition of second order to the Bose­-Einstein condensate, which exists in the temperature interval 0 ≤ T ≤ Tc . It is obtained that the condensation represents a discontinuity of the derivative of the specific heat at T = Tc .

scholarly journals Calculation of the T-P phase diagrams for the halogenomethane compounds (CCl-=SUB=-4-n-=/SUB=-Br-=SUB=-n-=/SUB=-, n=0, 1, 2, 4) using the mean field theory -=SUP=-*-=/SUP=-

2019 ◽  
Vol 61 (2) ◽  
pp. 339
Author(s):  
H. Yurtseven ◽  
S.B. Isik ◽  
E. Kilit Dogan
Keyword(s):  
Phase Diagrams ◽  
Mean Field Theory ◽  
Mean Field ◽  
Face Centered Cubic ◽  
Mean Field Model ◽  
Phase Line ◽  
Component Systems ◽  
Two Component Systems ◽  
The Mean ◽  
Face Centered

AbstractThe T – P phase diagrams of the halogenomethane compounds (CCl_4 – _ n Br_ n , n = 0, 1, 2, 4) are calculated using a mean field model. By expanding the free energy in terms of the order parameters for the transitions of the liquid (L), rhombohedral (R), face-centered cubic (FCC) and monoclinic (M) phases in those compounds, the phase line equations are derived and they are fitted to the experimental data from the literature. This method of calculating the T – P phase diagram is satisfactory to explain the T – P measurements for the halogenomethane compounds and it can also be applied to two-component systems.

scholarly journals Phase diagram of the selfinteracting particle­-antiparticle boson system

2021 ◽  
Vol 29 (1) ◽  
pp. 5-14
Author(s):  
D. Anchishkin ◽  
V. Gnatovskyy ◽  
D. Zhuravel ◽  
V. Karpenko
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
Phase Diagrams ◽  
Canonical Ensemble ◽  
Bose Condensate ◽  
Mean Field ◽  
Thermodynamic Quantities ◽  
Boson System ◽  
The Mean

A system of interacting relativistic bosons at finite temperatures and isospin densities is studied within the framework of the Skyrme­like mean­field model. The mean field contains both attractive and repulsive terms. The consideration is taken within the framework of the Canonical Ensemble and the isospin­density dependencies of thermodynamic quantities is obtained, in particular as the phase diagrams. It is shown that in such a system, in addition to the formation of a Bose­Einstein condensate, a liquid­gas phase transition is possible. We prove that the multi­boson system develops the Bose condensate for particles of high­density component only.

Single-Crystal Magnetic Properties of [Co(NH3)5(OH2)] [Cr(CN)6] Between 2 and 300 K

1992 ◽  
Vol 45 (11) ◽  
pp. 1899 ◽  
Author(s):  
PA Reynolds ◽  
CD Delfs ◽  
BN Figgis ◽  
B Moubaraki ◽  
KS Murray
Keyword(s):  
Ising Model ◽  
Field Model ◽  
Mean Field ◽  
Zero Field ◽  
Spin Orbit Coupling ◽  
Zero Field Splitting ◽  
Magnetic Exchange Interaction ◽  
Mean Field Model ◽  
Magnetic Exchange ◽  
The Mean

The magnetic susceptibilities along and perpendicular to the c axis (hexagonal setting) between 2.0 and 300 K at a magnetic field of 1.00 T, and the magnetizations at field strengths up to 5.00 T, are presented for single crystals of [Co(NH3)5(OH2)] [Cr(CN)6]. The results are interpreted in terms of zero-field splitting (2D) of the ground 4A2g term by spin-orbit coupling and of magnetic exchange interaction between the chromium atoms. The magnetic exchange is modelled as one of Ising or mean-field in type. The exchange is found to be quite small: J = -0.18(6) cm-1 if the Ising model is employed, and -0.03(1) cm-1 for the mean-field model. The model adopted for the exchange has a strong influence on the value of the parameter D obtained. When the Ising model is used D is deduced to be -0.28(9) cm-l; when the mean-field model is used D is -0.14(4) cm-l. The g-values deduced are in agreement with those from e.s.r. measurements at higher temperatures and do not depend on the exchange model. In any case, D is found to be sufficiently large that it must be considered in a polarized neutron diffraction experiment on the compound.

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