scholarly journals Magnetocaloric effect and piezoresponse of engineered ferroelectric- ferromagnetic heterostructures

2019 ◽  
Author(s):  
Chris Bowen
Keyword(s):  
Magnetic Field ◽  
Magnetocaloric Effect ◽  
Maxwell Equations ◽  
State Energy ◽  
Entropy Change ◽  
Zero Field ◽  
Multilayered Structures ◽  
Lattice Strains ◽  
Magnetization Data ◽  
Energy Conversion Devices

Present study reports the magnetocaloric effect (MCE) and piezoresponse of integrated ferroelectric-ferromagnetic heterostructures of PbZr0.52Ti0.48O3 (PZT) (5 nm)/ Bi-Sr-Ca-Cu2-OX (BSCCO) (5 nm)/ La0.67Sr0.33MnO3 (LSMO) (40 nm)/ MgO. Magnetic and pizoresponse behavior of the heterostructures are found to be governed by magneto-electric coupling and induced lattice strains. In addition, the MCE is studied using Maxwell equations from both Field Cooled (FC) and Zero Field Cooled (ZFC) magnetization data. Maximum MCE entropy change (|∆S|) of 42.6 mJkg-1K-1 (at 258 K) and 41.7 mJkg-1K-1 (at 269 K) are found corresponding to FC and ZFC data, respectively. The variation in maximum entropy change and corresponding temperatures for FC and ZFC data revealed that the application of a magnetic field can significantly contribute towards tuning of the MCE. Interestingly, these multilayered structures are found to sustain MCE over a broad temperature range, which makes them attractive for improved solid-state energy conversion devices.

scholarly journals Reversibility of the Magnetocaloric Effect in the Bean-Rodbell Model

2021 ◽  
Vol 7 (5) ◽  
pp. 60
Author(s):  
Luis M. Moreno-Ramírez ◽  
Victorino Franco
Keyword(s):  
Magnetic Field ◽  
Thermal Hysteresis ◽  
Entropy Change ◽  
Second Order ◽  
Zero Field ◽  
First Order ◽  
Magnetic Field Change ◽  
Magnetocaloric Materials ◽  
Moderate Magnetic Field ◽  
The Magnetic Field

The applicability of magnetocaloric materials is limited by irreversibility. In this work, we evaluate the reversible magnetocaloric response associated with magnetoelastic transitions in the framework of the Bean-Rodbell model. This model allows the description of both second- and first-order magnetoelastic transitions by the modification of the η parameter (η<1 for second-order and η>1 for first-order ones). The response is quantified via the Temperature-averaged Entropy Change (TEC), which has been shown to be an easy and effective figure of merit for magnetocaloric materials. A strong magnetic field dependence of TEC is found for first-order transitions, having a significant increase when the magnetic field is large enough to overcome the thermal hysteresis of the material observed at zero field. This field value, as well as the magnetic field evolution of the transition temperature, strongly depend on the atomic magnetic moment of the material. For a moderate magnetic field change of 2 T, first-order transitions with η≈1.3−1.8 have better TEC than those corresponding to stronger first-order transitions and even second-order ones.

Magnetic Properties and Magnetocaloric Effect of Gd3Ni in Crystalline and Amorphous States

2012 ◽  
Vol 190 ◽  
pp. 355-358 ◽  
Author(s):  
D.A. Shishkin ◽  
N.V. Baranov ◽  
A.V. Proshkin ◽  
S.V. Andreev ◽  
A.S. Volegov
Keyword(s):  
Magnetic Field ◽  
Magnetocaloric Effect ◽  
Entropy Change ◽  
Rapid Quenching ◽  
Antiferromagnetic Order ◽  
Cooling Power ◽  
Ferromagnetic Behavior ◽  
Field Change ◽  
Ni Alloy ◽  
Magnetic Field Change

The liquid quenched Gd3Ni alloy is observed to exhibit a ferromagnetic behavior below TC = 117 K unlike crystalline compound having an antiferromagnetic order at T < TN = 99 K. Rapid quenching from the melt results in a considerable enhancement of the magnetocaloric effect in Gd3Ni at low magnetic fields. The maximal value of the isothermal magnetic entropy change at a magnetic field change of 20 kOe for the amorphous Gd3Ni surpasses by more than 8 times the SM value for the polycrystalline counterpart. The relative cooling power for the amorphous Gd3Ni alloy is estimated as 265 J kg-1 and 676 J kg-1 at a magnetic field change of 20 kOe and 50 kOe, respectively.

scholarly journals Weak Singularities of the Isothermal Entropy Change as the Smoking Gun Evidence of Phase Transitions of Mixed-Spin Ising Model on a Decorated Square Lattice in Transverse Field

Entropy ◽  
2021 ◽  
Vol 23 (11) ◽  
pp. 1533
Author(s):  
Jozef Strečka ◽  
Katarína Karl’ová
Keyword(s):  
Magnetic Field ◽  
Phase Transitions ◽  
Ising Model ◽  
Magnetocaloric Effect ◽  
Entropy Change ◽  
Transverse Magnetic ◽  
Continuous Phase ◽  
Square Lattice ◽  
Mixed Spin ◽  
Weak Singularities

The magnetocaloric response of the mixed spin-1/2 and spin-S (S>1/2) Ising model on a decorated square lattice is thoroughly examined in presence of the transverse magnetic field within the generalized decoration-iteration transformation, which provides an exact mapping relation with an effective spin-1/2 Ising model on a square lattice in a zero magnetic field. Temperature dependencies of the entropy and isothermal entropy change exhibit an outstanding singular behavior in a close neighborhood of temperature-driven continuous phase transitions, which can be additionally tuned by the applied transverse magnetic field. While temperature variations of the entropy display in proximity of the critical temperature Tc a striking energy-type singularity (T−Tc)log|T−Tc|, two analogous weak singularities can be encountered in the temperature dependence of the isothermal entropy change. The basic magnetocaloric measurement of the isothermal entropy change may accordingly afford the smoking gun evidence of continuous phase transitions. It is shown that the investigated model predominantly displays the conventional magnetocaloric effect with exception of a small range of moderate temperatures, which contrarily promotes the inverse magnetocaloric effect. It turns out that the temperature range inherent to the inverse magnetocaloric effect is gradually suppressed upon increasing of the spin magnitude S.

Nanocomposites For magnetic Refrigeration

1992 ◽  
Vol 286 ◽  
Author(s):  
R.D. Shull ◽  
R.D. Mcmichael ◽  
J.J. Ritter ◽  
L.H. Bennett
Keyword(s):  
Magnetic Field ◽  
Heat Capacity ◽  
External Magnetic Field ◽  
Magnetocaloric Effect ◽  
Spin System ◽  
Entropy Change ◽  
Magnetic Nanocomposites ◽  
Magnetic Entropy ◽  
Effect Data ◽  
The Magnetic Field

ABSTRACTUpon the application of an external magnetic field, the magnetic spins in a material partially align with the field, thereby reducing the magnetic entropy of the spin system. When performed adiabatically, the specimen's temperature will rise. This temperature rise, δT, related to the entropy change by the heat capacity, is known as the magnetocaloric effect. Upon cycling the magnetic field, this effect can be used for transferring heat from one thermal reservoir to another, forming the basis for a magnetic refrigerator. Recently, NIST scientists predicted composite magnetic materials containing nanometer-size magnetic species could possess enhanced magnetocaloric effects [1-2], especially at high temperatures or low magnetic fields. Magnetic nanocomposites may be prepared in many different ways, and recent magnetocaloric effect data measured on Fe-doped gadolinium gallium garnets are presented to show both the effect of processing and a methodology for optimizing δT.

The Magnetocaloric Effect and Magnetic Transitions in Hydride Compounds: GdNiH3.2 and TbNiH3.4

2015 ◽  
Vol 233-234 ◽  
pp. 243-246
Author(s):  
A.I. Smarzhevskaya ◽  
S.A. Nikitin ◽  
Viktor N. Verbetsky ◽  
Wacław Iwasieczko ◽  
Alexey N. Golovanov
Keyword(s):  
Magnetocaloric Effect ◽  
Magnetic Entropy Change ◽  
Entropy Change ◽  
Magnetic Entropy ◽  
Magnetic Transitions ◽  
Isothermal Magnetization ◽  
Magnetocaloric Properties ◽  
Magnetization Data

The paper presents the investigation of GdNiH3.2 and TbNiH3.4 hydrides magnetic transitions and magnetocaloric properties. The isothermal magnetization data in the fields up to 5T are obtained for GdNi and TbNi compounds and their hydrides and the values of magnetic entropy change are calculated. The maximum values of magnetic entropy change ΔSM in GdNiH3.2 and TbNiH3.4 are extremely large. It is shown that the hydrogenation shifts ΔSM(T) maximum to lower temperatures.

Toward an Experimental Design Approach for Magnetocaloric Refrigeration Systems

2016 ◽  
Author(s):  
Ivan Bernal ◽  
Hector Guido ◽  
Spencer Rautus ◽  
Joseph Piacenza
Keyword(s):  
Magnetic Field ◽  
Magnetocaloric Effect ◽  
Heat Carrier ◽  
Large Scale ◽  
Experimental Testing ◽  
Entropy Change ◽  
High Heat ◽  
Field Exposure ◽  
Design Variables ◽  
The Impact

The magnetocaloric effect (MCE) is a magneto-thermodynamic phenomenon that heats and cools specific alloys through exposure to an alternating magnetic field. This phenomenon has the potential to create a temperature difference in a heat carrier mimicking a conventional vapor compression refrigeration cycle without harmful chemical byproducts. This research investigates the design of an experimental testing mechanism for identifying key interactions between design variables, while maximize temperature differential Key noise parameters (KNP). Fluid flow rate, magnetic field exposure time, and variations in heat exchanger configuration are explored. Understanding the significant interactions between these variables will lead to the design of a functional prototype that serves as a basis for future development in applications of the MCE for large-scale cooling systems. In this work, elemental gadolinium is used due to its high magnetic entropy change, and consequently high reversible temperature change when exposed to a magnetic field. An aqueous propylene glycol solution serves as the heat carrier based on its high heat capacity and basic pH level, reducing the possibility of degradation within the magnetocaloric material. The magnetic field is supplied by a grade N52 magnet with a magnetic field strength of approximately 0.9 Tesla. Based on this analysis, a concept stage design for experimentally maximizing the impact of the magnetocaloric effect is presented.

The Influence of the Purity of Gd on the Magnetocaloric Effect in Gd5Si2-XGe2-XZn2x Alloys

2011 ◽  
Vol 685 ◽  
pp. 311-315
Author(s):  
Zhi Zeng ◽  
Xue Zhen Wang ◽  
Jian Huang ◽  
Jie Xiang ◽  
Xue Ling Hou
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetocaloric Effect ◽  
Curie Point ◽  
Magnetic Entropy Change ◽  
Entropy Change ◽  
Magnetic Entropy ◽  
Field Change ◽  
Magnetic Field Change ◽  
Giant Magnetocaloric Effect

Gd5Si2Ge2-based alloys can exhibit a giant magnetocaloric effect (GMCE) which gives them the potential use in the cooling technologies[1].Through this studies, it can be found that the purity of Gd had a great impact on the magnetocaloric effect in Gd5Si2-xGe2-xZn2x alloys. When 3N Gd used and 2x=0.01, Gd5Si2-xGe2-xZn2x around the curie point of 280k get the maximum magnetic entropy change of 14.0 J/(Kg.K) under the external magnetic field change from 0 to 1T, but when 2N Gd used and 2x=0.05, Gd5Si2-xGe2-xZn2x around the curie point of 284.2k under the external magnetic field change 1T get the maximum magnetic entropy change 6.65 J/(Kg.K).

scholarly journals Magnetocaloric Effect in Cu5-NIPA Molecular Magnet: A Theoretical Study

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 485 ◽  
Author(s):  
Karol Szałowski ◽  
Pamela Kowalewska
Keyword(s):  
Magnetic Field ◽  
Magnetocaloric Effect ◽  
Theoretical Study ◽  
Canonical Ensemble ◽  
Entropy Change ◽  
Molecular Magnet ◽  
Wide Range ◽  
Magnetocaloric Properties ◽  
Magnetic Specific Heat ◽  
High Degree

We calculated the magnetocaloric properties of the molecular nanomagnet Cu5-NIPA, consisting of five spins S = 1 / 2 arranged in two corner-sharing triangles (hourglass-like structure without magnetic frustration). The thermodynamics of the system in question was described using the quantum Heisenberg model solved within the field ensemble (canonical ensemble) using exact numerical diagonalization. The dependence of the magnetic entropy and magnetic specific heat on the temperature and the external magnetic field was investigated. The isothermal entropy change for a wide range of initial and final magnetic fields was discussed. Due to plateau-like behavior of the isothermal entropy change as a function of the temperature, a high degree of tunability of magnetocaloric effect with the initial and final magnetic field was demonstrated.

The Effect of Plastic Deformation on Magnetic and Magnetocaloric Properties of Gd90Ga10 Alloy

2016 ◽  
Vol 845 ◽  
pp. 56-60 ◽  
Author(s):  
Sergey Taskaev ◽  
Konstantin Skokov ◽  
Dmitriy Karpenkov ◽  
Vladimir V. Khovaylo ◽  
Maxim N. Ulyanov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Treatment ◽  
Plastic Deformation ◽  
Magnetocaloric Effect ◽  
Entropy Change ◽  
High Temperature Heat Treatment ◽  
Magnetocaloric Properties ◽  
Temperature Heat ◽  
Cold Rolled ◽  
Temperature Heat Treatment

In this work we report the results of experimental investigation of the magnetocaloric effect in Gd90Ga10 cold rolled ribbons. A moderate entropy change ΔS = 3.5 J/(kg·K) and magnetocaloric effect ΔT = 3.4K was observed for the as-cast materials in an external magnetic field of 2T which is less by 35% in comparison with the pure gadolinium metal. It was found that a significant (up to 70%) depression of magnetization and magnetocaloric properties developed in the course of plastic deformation can be completely restored by means of a high temperature heat treatment.

scholarly journals Simulated thermomagnetic properties of DyAl2, HoAl2 and ErAl2 compounds in comparison with the results for TbAl2, GdAl2 and SmAl2 compounds calculated by ATOMIC MATTERS MFA Computation System

2018 ◽  
Author(s):  
Rafał Michalski ◽  
Jakub Zygadło ◽  
Tomasz Lanczewski
Keyword(s):  
Magnetic Field ◽  
Electronic Structure ◽  
External Magnetic Field ◽  
Thermal Evolution ◽  
Entropy Change ◽  
Electronic Systems ◽  
Zero Field ◽  
Calculation Methodology ◽  
Thermomagnetic Properties ◽  
Parameter Values

We present the results of calculations of magnetic properties of 3 compounds from Laves phase C15 family: DyAl2, HoAl2 and ErAl2 performed with a new computation system called ATOMIC MATTERS MFA. We compare these findings with the recently published results for TbAl2, GdAl2 and SmAl2. The calculation methodology was based on the localized electron approach applied to describe the thermal evolution electronic structure of rare-earth R3+ ions over a wide temperature range and to compute magnetocaloric effect (MCE). Thermomagnetic properties were calculated based on the fine electronic structure of 4f9, 4f10 and 4f11 configurations of the Dy3+, Ho3+, Er3+ ions, respectively. Our calculations yield the magnetic moment value and direction; single-crystalline magnetization curves in zero field and external magnetic field applied in various directions of m(T, Bext); the 4f-electronic components of specific heat c4f(T, Bext); and temperature dependence of the magnetic entropy and isothermal entropy change with external magnetic field -S(T, Bext). The cubic CEF parameter values used for DyAl2 calculations are taken from earlier research of A.L. Lima, A.O. Tsokol and recalculated for universal cubic parameters (Amn) for the RAl2 series. Our studies reveal the importance of multipolar charge interactions when describing thermomagnetic properties of real 4f electronic systems and the effectiveness of an applied self-consistent molecular field in calculations for magnetic phase transition simulation.

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