Influence of the demagnetizing factor on the magnetocaloric effect: Critical scaling and numerical simulations

Romero‐Muñiz, Carlos; Ipus, J.J.; Blázquez, J.S.; Franco, V.; Conde, A.

doi:10.1063/1.4885110

Cited by 41 publications

(16 citation statements)

References 27 publications

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“…[113][114][115][116][117] Considering the case of the depolarizing field in ferroelectrics, its influence on electrocaloric properties is ignored in most studies. This is because for strongly polar materials, such as ferroelectrics,…”

Section: G Depolarizing Fieldmentioning

confidence: 99%

Direct and indirect measurements on electrocaloric effect: Recent developments and perspectives

Liu

Scott

Dkhil

2016

Applied Physics Reviews

237

150

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It has been ten years since the discovery of the giant electrocaloric effect in ferroelectric materials showed that it is possible to employ this effect for substantial cooling applications. This last decade has been marked by increasing research interest, especially in characterizing and measuring the electrocaloric effect using both the so-called indirect and direct approaches. In this context, a comprehensive summary and careful reexamination of these approaches are very timely and of great importance to justify the assumptions used in different measurement techniques. This review is therefore dedicated to cover recent important and rapid advances from both the indirect and direct measurements and provides critical insights relevant for quantifying the electrocaloric effect. It involves electrocaloric materials from normal ferroelectrics, antiferroelectrics, and relaxors, and it fundamentally focuses on how the electrocaloric entropy changes in response to electric field in these typical electrocalorics. The article addresses recent developments, especially during the past three years, such as technical selection of proper polarization-electric field loops, negative electrocaloric effect in antiferroelectrics and relaxors, the controversial debate on the indirect method in relaxors, the important role of field dependence of specific heat, kinetic factors, and so on. Moreover, this review also is concerned with extracting reliable data by direct measurements. Four typical techniques and devices used recently, such as thermocouples, differential scanning calorimeters, specifically designed calorimeters, and scanning thermal microscopy, are briefly reviewed, while infrared cameras are emphasized. We hope that our review will not only provide a useful background to understand fundamentally the electrocaloric effect and what one really measures but also may act as a practical guide to exploit and develop electrocalorics towards the design of suitable devices. Published by AIP Publishing. [http://dx

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Section: G Depolarizing Fieldmentioning

confidence: 99%

Direct and indirect measurements on electrocaloric effect: Recent developments and perspectives

Liu

Scott

Dkhil

2016

Applied Physics Reviews

237

150

View full text Add to dashboard Cite

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“…Another advantage of this equation is the wide range of applicability, which has been proved to be valid for t(M/H) −1/β 25 within errors of less than 1% [86]. Moreover, this equation has been used to extract valuable information in the context of MCE such as composite materials [87] or the demagnetizing factor [82]. Nevertheless, it is worth noting that this type of equations of state are constructed by applying the critical scaling in the whole range of applied field and temperature, which means that in these models a real saturation in magnetization is never reached.…”

Section: Other Remarksmentioning

confidence: 99%

Applicability of scaling behavior and power laws in the analysis of the magnetocaloric effect in second-order phase transition materials

et al. 2016

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In recent years, universal scaling has gained renewed attention in the study of magnetocaloric materials. It has been applied to a wide variety of pure elements and compounds, ranging from rare-earth-based materials to transition metal alloys, from bulk crystalline samples to nanoparticles. It is therefore necessary to quantify the limits within which the scaling laws would remain applicable for magnetocaloric research. For this purpose, a threefold approach has been followed: (a) the magnetocaloric responses of a set of materials with Curie temperatures ranging from 46 to 336 K have been modeled with a mean-field Brillouin model, (b) experimental data for Gd has been analyzed, and (c) a 3D-Ising model-which is beyond the mean-field approximation-has been studied. In this way, we can demonstrate that the conclusions extracted in this work are model-independent. It is found that universal scaling remains applicable up to applied fields, which provide a magnetic energy to the system up to 8% of the thermal energy at the Curie temperature. In this range, the predicted deviations from scaling laws remain below the experimental error margin of carefully performed experiments. Therefore, for materials whose Curie temperature is close to room temperature, scaling laws at the Curie temperature would be applicable for the magnetic field range available at conventional magnetism laboratories (∼10 T), well above the fields which are usually available for magnetocaloric devices.

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“…Despite the importance of demagnetizing field for the correct characterization of the samples, the applied field is seldom corrected to the internal field. [37][38][39][40][41][42][43][44] This correction can be done using N D = 1/3 for loosely spherical powder samples or for spherical powder in a spherical pack, which is derived from the expression: [45] …”

Section: Effect Of the Demagnetizing Fieldmentioning

confidence: 99%

Analysis of the Magnetocaloric Effect in Powder Samples Obtained by Ball Milling

Blázquez

Ipus

Moreno-Ramírez

et al. 2015

Metallurgical and Materials Transactions E

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Since the discovery of the giant magnetocaloric effect (MCE) close to room temperature in FeRh and particularly in Gd 5 Si 2 Ge 2 compounds, the study of this phenomenon has experienced an exponential growth. Among the different techniques used to produce magnetocaloric materials, ball milling has been shown as a very versatile one and presents several advantages over other preparation techniques (e.g., easy scale-up to industrial production). Although a general decrease of the peak value of the magnetic entropy change is observed for milled samples, it can be compensated by the large broadening of the MCE peak, leading to an increase of the refrigeration capacity. In this short review, several aspects inherent to powder samples affecting MCE will be discussed, such as the relevant effect of the demagnetizing field, the possible multiphase character, and the presence of Curie temperature distributions. In mechanically alloyed samples, the two latter factors are typically affected by the degree of integration of the different starting constituents.

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Influence of the demagnetizing factor on the magnetocaloric effect: Critical scaling and numerical simulations

Abstract: Articles you may be interested in Y-doped La0.7Ca0.3MnO3 manganites exhibiting a large magnetocaloric effect and the crossover of first-order and second-order phase transitions J. Appl. Phys. 118, 143902 (2015)

Cited by 41 publications

References 27 publications

Direct and indirect measurements on electrocaloric effect: Recent developments and perspectives

Direct and indirect measurements on electrocaloric effect: Recent developments and perspectives

Applicability of scaling behavior and power laws in the analysis of the magnetocaloric effect in second-order phase transition materials

Analysis of the Magnetocaloric Effect in Powder Samples Obtained by Ball Milling

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