Thermal Hysteresis Control in Fe49Rh51 Alloy through Annealing Process

We report the results of studies of the magnetic and transport properties of Fe49Rh51 alloy prepared by different sequences of quenching and the annealing process. The temperature dependences of the relative initial magnetic permeability and resistivity are analyzed. An optimal regime consisting of annealing at 1300 K for 440 min and quenching from 1300 K to 275 K is found to observe the desired narrow antiferromagnetic–ferromagnetic transition in Fe49Rh51 alloy under cyclic conditions. This has the potential to increase the efficiency of cooling devices based on the magnetocaloric effect of magnetic materials with a first-order field-induced phase transition.

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Hypersonic and Dielectric Studies of Relaxor Ferroelectric Single Crystal

MRS Proceedings ◽

10.1557/proc-604-185 ◽

1999 ◽

Vol 604 ◽

Author(s):

Chi-Shun Tu ◽

V.H. Schmiidt ◽

C.-H. Yeh ◽

L.-F. Chen ◽

C.-L. Tsai

Keyword(s):

Phase Transition ◽

Dielectric Permittivity ◽

Single Crystal ◽

Thermal Hysteresis ◽

Relaxor Ferroelectric ◽

Dipolar Relaxation ◽

First Order ◽

Dielectric Data ◽

Scattering Spectra ◽

Ferroelectric Single Crystal

AbstractBoth the longitudinal (LA) Brillouin back-scattering spectra and dielectric permittivity along the [001] direction have been measured as a function of temperature for a relaxor ferroelectric single crystal (PbMg1/3Nb2/3O3)0.68(PbTiO3)0.32 (PMN-32%PT). A sharp ferroelectric phase transition (which is associated with a Landau-Khalatnikov-like phonon damping maximum) was observed near 445 K. As temperature increases, a diffuse phase transition was detected near 280 K. In addition, the nature of the thermal hysteresis for the dielectric permittivity confirms that these transitions (near 280 and 445 K for heating procedure) are diffuse first-order and first-order, It respectively. The dielectric data prove the existence of an electric dipolar relaxation process below 300 K.

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Ultrasonic Relaxation in Phase Transition Region in Ferroelectric Semiconductors of Sn2P2S6 Family

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.184.345 ◽

2012 ◽

Vol 184 ◽

pp. 345-350

Author(s):

Vytautas Samulionis ◽

Juras Banys ◽

Yulian Vysochanskii

Keyword(s):

Phase Transition ◽

Ultrasonic Velocity ◽

Thermal Hysteresis ◽

Ultrasonic Attenuation ◽

Landau Theory ◽

Velocity Change ◽

First Order ◽

Temperature Range ◽

Large Hysteresis ◽

Relative Change

The paper presents recent results of ultrasonic investigation of Sn2P2S6 family ferroelectric crystals and their solid solutions in the temperature range 100-300 K. It was shown that in Sn2P2(S,Se)6 crystals the critical ultrasonic velocity slowing down for longitudinal waves propagating along main crystallographic directions is quite sharp and large. The relative change of longitudinal ultrasonic velocity along z-axis at the phase transition gradually increased from 10 % in pure Sn2P2S6 till 25 % for sample with 0.4 content of Se. Such large velocity change causes the large ultrasonic attenuation anomaly. The increase of relaxation time: τ=τ0/(TC-T) leads to the increase of attenuation. Prefactor τ0 was shown to be very small and the critical attenuation anomaly arises in the narrow temperature range close to phase transition. In the 0.4 Se sample the phase transition is of the first order because small thermal hysteresis exists. The ultrasonic velocity behaviour in the ferroelectric phase was described using Landau theory and free energy expansion including sixth order terms. For (Sn,Pb)2P2S6 system the critical ultrasonic anomalies were smaller and the phase transition temperature substantially decreased (for 0.45 Pb sample the phase transition point was at Tc =140 K). The ultrasonic anomalies at phase transition in (PbxSn1-x)2P2S6 have large hysteresis showing that transition is of the first order, far from the critical point.

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First-Order Ferromagnetic Transition of Quantum Spin Ice System Yb2Ti2O7

SPIN ◽

10.1142/s2010324715400020 ◽

2015 ◽

Vol 05 (02) ◽

pp. 1540002 ◽

Cited By ~ 2

Author(s):

Yukio Yasui ◽

Noriaki Hamachi ◽

Yohei Kono ◽

Shunichiro Kittaka ◽

Toshiro Sakakibara

Keyword(s):

Neutron Diffraction ◽

Specific Heat ◽

Single Crystals ◽

Thermal Hysteresis ◽

Hysteresis Loops ◽

Quantum Spin ◽

Ferromagnetic Transition ◽

Spin Ice ◽

First Order ◽

Quantum Spin Ice

The neutron diffraction and measurements of specific heat and magnetization were carried out on single crystals of a quantum spin ice system Yb 2 Ti 2 O 7. The thermal hysteresis loops of temperature dependence of the magnetization and neutron diffraction intensity indicate a first-order ferromagnetic transition, where the used single crystals are confirmed to have a sharp peak structure in the specific heat (C)–temperature (T) curve at T C ∼ 0.2 K. The magnetic structure analysis of neutron diffraction results revealed that the Yb 3+ moments have a ferromagnetic collinear structure along [001] directions with ordered moment value 1.1 ± 0.1 μB at 0.03 K. The mechanism of ferromagnetic transition of Yb 2 Ti 2 O 7 will be discussed.

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Ordering and disordering in anisotropic L10-FePd

MRS Proceedings ◽

10.1557/proc-753-bb5.37 ◽

2002 ◽

Vol 753 ◽

Cited By ~ 2

Author(s):

A. Kulovits ◽

W. A. Soffa ◽

W. Püschl ◽

W. Pfeiler

Keyword(s):

Phase Transition ◽

Thermal Equilibrium ◽

Isothermal Annealing ◽

Thermal Hysteresis ◽

Annealing Treatment ◽

Internal Stresses ◽

Small Step ◽

First Order ◽

First Order Phase Transition ◽

First Order Phase

ABSTRACTNearly equiatomic FePd (Fe-52at.%Pd) alloys have been deformed by cold-rolling to 60% thickness reduction. Ordering and disordering was studied during isochronal and isothermal annealing by residual resistometry (REST) in the deformed as well as in the recrystallized state. In both cases a first order phase transition with a broad thermal hysteresis is observed. Resistivity values corresponding to thermal equilibrium of LRO-states, however, result lower in the deformed case. This is interpreted as a consequence of internal stresses leading to a preference of one variant of ordered domains and consequently to a higher degree of LRO.A detailed study by an isothermal small-step annealing treatment yields two counteracting exponential processes during order-order relaxation with an activation energy of 2.7eV and 2.4eV, respectively.

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PRETRANSITIONAL PHENOMENA IN REGION OF STRUCTURAL PHASE TRANSITION IN SODIUM PERCHLORATE

IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA ◽

10.6060/ivkkt.20206301.6042 ◽

2019 ◽

Vol 63 (1) ◽

pp. 64-70

Author(s):

Amil R. Aliev ◽

Isa R. Akhmedov ◽

Murad G. Kakagasanov ◽

Zakir A. Aliev ◽

Sergey P. Kramynin

Keyword(s):

Phase Transition ◽

Transition Temperature ◽

Phase Transition Temperature ◽

Structural Phase Transition ◽

Structural Phase ◽

Sodium Perchlorate ◽

First Order ◽

Temperature Range ◽

Temperature Dependences ◽

Increasing Temperature

Structural and dynamic properties and molecular relaxation processes in crystalline sodium NaClO4 perchlorate in the temperature range from 300 K to 650 K were studied by Raman spectroscopy. The temperature dependences of the position of the maximum v (frequency), the width w and the intensity I of the spectral band, corresponding to the fully symmetric vibration v1(A) of the ClO4–1 perchlorate ion, in the spectral range from 933 cm–1 to 944 cm–1 were analyzed. The frequency v and intensity I decrease, and the width w increases with the increasing temperature. It is shown that these temperature dependences have certain features at a temperature of 460 K. With a further increase in temperature, the frequency v decreases more rapidly, the width w increases, and the intensity I decreases more intensively. In the temperature range from 460 K to the temperature Tstr = 581 K of the first order structural phase transition, we observe a deviation of the temperature dependence of the frequency and width from the linear dependences characteristic of lower temperatures. These deviations appear at a temperature of 460 K and increase with the increasing temperature and approaching the phase transition temperature. It has been established that in the crystalline sodium perchlorate NaClO4 a structural first-order phase transition is stretched. At the phase transition temperature (Tstr = 581 K), the width increases sharply, and the frequency decreases sharply, decreasing with a further increase in temperature. The existence of a pretransitional region in the studied crystalline sodium perchlorate NaClO4 was found. This pre-transition region occurs in the temperature range from 460 K to Tstr = 581 K.

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Thermal hysteresis across the first-order phase transition in the (Na0.5Bi0.5)1−xBaxTiO3dielectric system

Phase Transitions ◽

10.1080/01411590500404901 ◽

2005 ◽

Vol 78 (12) ◽

pp. 895-904

Author(s):

Sujeet Chaudhary ◽

Anil K. Sisodia ◽

Dinesh C. Dube

Keyword(s):

Phase Transition ◽

Order Phase Transition ◽

Thermal Hysteresis ◽

First Order ◽

First Order Phase Transition ◽

First Order Phase

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A First Order Phase Transition Studied by an Ising-Like Model Solved by Entropic Sampling Monte Carlo Method

Symmetry ◽

10.3390/sym13040587 ◽

2021 ◽

Vol 13 (4) ◽

pp. 587

Author(s):

Jorge Linares ◽

Catherine Cazelles ◽

Pierre-Richard Dahoo ◽

Kamel Boukheddaden

Keyword(s):

Phase Transition ◽

Monte Carlo ◽

Order Phase Transition ◽

Thermal Hysteresis ◽

Surface Effects ◽

Gradual Transition ◽

First Order ◽

First Order Phase Transition ◽

Entropic Sampling ◽

First Order Phase

Two-dimensional (2D) square, rectangular and hexagonal lattices and 3D parallelepipedic lattices of spin crossover (SCO) compounds which represent typical examples of first order phase transitions compounds are studied in terms of their size, shape and model through an Ising-like Hamiltonian in which the fictitious spin states are coupled via the respective short and long-range interaction parameters J, and G. Furthermore, an environmental L parameter accounting for surface effects is also introduced. The wealth of SCO transition properties between its bi-stable low spin (LS) and high spin (HS) states are simulated using Monte Carlo Entropic Sampling (MCES) method which favors the scanning of macro states of weak probability occurrences. For given J and G, the focus is on surface effects through parameter L. It is shown that the combined first-order phase transition effects of the parameters of the Hamiltonian can be highlighted through two typical temperatures, TO.D., the critical order-disorder temperature and Teq the equilibrium temperature that is fixed at zero effective ligand field. The relative positions of TO.D. and Teq control the nature of the transition and mediate the width and position of the thermal hysteresis curves with size and shape. When surface effects are negligible (L = 0), the equilibrium transition temperature, Teq. becomes constant, while the thermal hysteresis’ width increases with size. When surface effects are considered, L ≠ 0, Teq. increases with size and the first order transition vanishes in favor of a gradual transition until reaching a threshold size, below which a reentrance phenomenon occurs and the thermal hysteresis reappears again, as shown for hexagonal configuration.

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Effect of Nd Substitution on the Structural and Magnetocaloric Properties of Gd5Si2Ge2

Materials Science Forum ◽

10.4028/www.scientific.net/msf.830-831.501 ◽

2015 ◽

Vol 830-831 ◽

pp. 501-504

Author(s):

Bhagya Uthaman ◽

Manoj Raama Varma

Keyword(s):

Phase Transition ◽

Curie Temperature ◽

Magnetic Transition ◽

Ferromagnetic Transition ◽

First Order ◽

Arc Melting ◽

First Order Phase Transition ◽

Magnetocaloric Properties ◽

Nd Substitution ◽

First Order Phase

In the present work, Nd substituted Gd5-xNdxSi2Ge2 with x = 0.05, 0.1 and 0.2 have been synthesized by arc melting and the effect of Nd substitution on the structural and magnetocaloric properties of Gd5Si2Ge2 has been investigated. The composition with x=0.05 undergoes a first order phase transition with a Curie temperature of 275 K. With the increase in Nd content to x=0.1 and x=0.2, the compounds undergo a second order magnetic transition at 300 K and 293 K respectively. Maximum entropy changes (-ΔSM) for Gd5-xNdxSi2Ge2 alloys with x = 0.05, 0.1 and 0.2 are 12.8, 7.6 and 7.2 J/kg K, respectively, for 50 kOe. The critical exponent analysis of the paramagnetic to ferromagnetic transition and the scaling behaviour of field dependence of MCE for x=0.1 and 0.2 compositions is also carried out.

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Упругие свойства монокристаллов La-=SUB=-0.7-y-=/SUB=-Pr-=SUB=-y-=/SUB=-Ca-=SUB=-0.3-=/SUB=-MnO-=SUB=-3-=/SUB=- (0≤ y≤0.3)

Физика твердого тела ◽

10.21883/ftt.2019.11.48429.522 ◽

2019 ◽

Vol 61 (11) ◽

pp. 2199

Author(s):

Р.И. Зайнуллина

Keyword(s):

Phase Transition ◽

Internal Friction ◽

Magnetic Phase ◽

Structural Phase ◽

Paramagnetic State ◽

Temperature Hysteresis ◽

Velocity Of Sound ◽

First Order ◽

Temperature Dependences ◽

Order Magnetic Phase Transition

Results of the investigation of the temperature dependences of the velocity of longitudinal sound and internal friction in the ferromagnetic La 0.7-y Pr y Ca 0.3 MnO3 single crystals (0≤ y≤0.3) with first-order magnetic phase transition are presented. In the paramagnetic state, the temperature dependences of the velocity of sound and the internal friction demonstrate extended temperature hysteresis, which indicates the ingomogeneity of the paramagnetic state. It seems likely that the main reason of this ingomogeneity is structural phase separation.

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