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Abstract — Magnetic refrigeration investigated as an efficient

environmentally friendly and flexible alternative to conventional

vapor compression systems. This magnetic technology complete

with an important part of the Magnetocaloric material which

must be subjected to the magnetic field generates by magnets use.

A large effort invested in improving the magnetocaloric material,

discoveries of outstanding materials provided new opportunities

to use them as alternative working materials in active magnetic

refrigeration at various temperatures. It is believed that the

manganite materials with the superior magnetocaloric properties

in addition to cheap materials processing cost will be the option

of future magnetic [1]. This paper present an overview of

different published magnetocaloric materials used in magnetic

refrigeration applications over the past few years, analyze the

different efficiency, the usability for these materials based on

magnetic flux density used, the temperature span result and

others. Thus allows us to present recommendations for

improving existing magnetocaloric materials as well as discussing

the features of the best magnetocaloric material for magnetic

refrigeration. Lastly it remains the responsibility of decision-

makers to choose the most appropriate ones.

Index Terms — Magnetic Refrigeration, Magnetocaloric

Materials, Magnetocaloric Effect, (MCE) & Curie temperature,

(𝑻𝒄𝒖𝒊𝒓𝒆).

I.INTRODUCTION

The Earth is in serious danger of increasing its temperature

due to the greenhouse gases resulting mainly from the burning

of fossil fuels in the generation of electricity and transport [1,

2]. In addition, the contaminants produced by burning fossil

fuels represent a health hazard that cannot be exceeded [3, 4].

Most studies have shown that air conditioning for human

comfort takes up 30-40% of the electricity produced [5].

Although the air conditioning and refrigeration industry has

developed significantly, it still relies on conventional cooling

technology based on compression and expansion of refrigerant

fluids [6]. Researchers are currently developing a new

technique called magnetic fermentation based mainly on

magnetic materials.

Aedah M. Jawad Mahdy is with Middle Technical University, Technical

Engineering College / Baghdad, Iraq, (e-mail aida200899@yahoo.com).

The magnetocaloric material has an essential part as well as

magnet in magnetic refrigeration. Although a number of

review articles on magnetic refrigeration devices have been

published these mainly have concerned themselves with the

temperature span and cooling power of the devices, and little

effort made to compare existing magnetocaloric materials used

in detail. It is important to investigate the magnetocaloric

materials that used because it's can be expensive part as well

as the magnet. Considering the commercial viability of

magnetic refrigeration it is extremely important as the

magnetocaloric materials must generates a high temperature

span when exposed to a magnetic flux density over the

minimum amount of magnet possible [7].

This study review and compare different magnetocaloric

materials assemblies, showing which perform best, hopes to

learn some fundamental key features that must be present in

efficient magnetic refrigeration devices design to improve the

efficiency. In consequence is enabling technology to replace

the conventional gas compression (CGC) technology in the

near future.

II.BACKGROUND

A. Magnetocaloric Effect (MCE) & Curie Temperature

The Magnetocaloric Effect is one of the most fundamental

physical properties of Magnetic Materials, describes the

behavior of a magnetic solid when exposed to changing

magnetic field [8]. The applied magnetic field causes the

magnetic spin domains to align in a manner that decreases the

internal disorder of the material, resulting in a decrease in the

magnetic portion of the entropy in the system, Fig. (1). Its

temperature may increase or decreased, in ferromagnetic

materials near the ordering temperature, 𝑇𝑐𝑢𝑖𝑟𝑒, the

temperature above which it loses its ferromagnetic ability [9].

The extent of the temperature is difference between the final

and the initial state of the material, dependent on numerous

intrinsic and extrinsic factors. Chemical composition, crystal

structure, and the magnetic state are among the most important

intrinsic material parameters that determine its MCE. The

extrinsic factors include temperature, the surrounding

pressure, the sign of the magnetic field change, that whether

the magnitude of the magnetic field has been raised or

lowered, [8]. So, different MCMs have different values of

Curie temperature, operating more work than away from the

Curie point. The material doing the greatest magnetic work

Overview for published Magnetocaloric

Materials used in Magnetic Refrigeration

applications

Aedah M. Jawad Mahdy

International Journal of Computation and Applied Sciences IJOCAAS, Volume3, Issue 1, August 2017, ISSN: 2399-4509

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will be the material operating at a temperature with the largest

MCE [10].

Fig. (1): The alignment of a randomly ordered magnetic spin system by an

external magnetic field. (a) Without an external magnetic field. (b) Whit

external magnetic field applied [11].

B. Magnetocaloric Materials (MCMs)

The materials exhibiting large, reversible temperature changes

in response to changing magnetic fields are usually referred as

Magnetocaloric Materials [8], generally largest near Curie

temperature. It is important to consider the order of the phase

transition, i.e. the order of the lowest differential of the free

energy which shows a discontinuity at the transition [12].

There are two types of magnetic phase changes that may occur

at the Curie point:

- First Order Magnetic Transition (FOMT), the most

notable examples are Ferrum-Rhodium (FeRh) and

Giant magnetocaloric effect material, (GMCE).

- Second Order Magnetic Transition (SOMT),

Gadolinium and its Alloys.

The MCE can be much larger in magnitude in FOMT than

SOMT materials, but generally occurs over a smaller range of

temperatures [9], with a phase transition that involves a

discontinuity in the first derivative of free energy with respect

to a thermodynamic variable [13]. A large MCE (i.e. GMCE)

due to the fact that in addition to normal magnetic entropy

associated with magnetic ordering, there is a second

contribution the entropy associated with the structural change

in materials which exhibit a magnetic-structural

transformation [14].

In SOMT materials, there is no latent heat and the peak of the

magnetocaloric properties is wide and smooth, Fig. (2), a

phase transition with continuous first derivatives of free

energy, pay respect to either temperature or applied field, but

discontinuous at second derivatives. Magnetocaloric effect is a

consequence of a reduction in the heat capacity when exposed

to a magnetic field. Additionally, SOMT materials exhibit

negligible magnetic hysteresis [9].

There are several problems, one of which is the hysteresis

inherently associated with first order transitions. It may be

possible to reduce the hysteresis, but never eliminate it, by

increasing the purity, and/or grain size, and perhaps by

alloying an appropriate impurity element, by carefully packing

regenerator beds with the appropriate alloy compositions. In

addition to the time dependence associated with these first

order transformations, on the order of minutes to realize the

full MCE, especially ΔTad, [14]. This time lag associated the

FOMT material may decrease cycle performance by 30-50%,

[15].

B1. The Benchmark Magnetocaloric Material: -

B1.a Gadolinium and it's Alloys:-

Gadolinium (𝐺𝑑),is a rare-earth, chemical element, do not

exist in nature all by itself, originally found in a black stone,

called Cerite, discovered by Johan Gadolin after which the

element eventually named [16]. It is a soft, shiny, ductile,

silvery metal belonging to the Lanthanide group of the

periodic chart. Gadolinium becomes superconductive below

1083K, is a SOMT material with a Curie temperature

approximately 293K. It’s strongly magnetic at room

temperature, and the only pure substance with a Curie point

near room temperature that exhibits a significant MCE over a

large temperature span [15], its Curie temperature cannot be

adjusted readily. It’s truly a benchmark magnetic refrigerant

material that exhibits excellent magnetocaloric properties and

difficult to improve upon, it's rather expensive. Not

surprisingly, the metal has been employed in each of the early

demonstrations of near-ambient cooling by the MCE [8]. The

metal does not tarnish in dry air but an oxide film forms in

moist air and can corrode in the presence of water at room

temperature, which can be eliminated using Gd-based. So, it is

of interest to search for cheaper materials exhibit better

performance than of 𝐺𝑑, by alloyed with Terbium (𝑇𝑏),

Dysprosium (𝐷𝑦) or Erbium (𝐸𝑟), in order to lower the 𝑇𝐶𝑢𝑟𝑖𝑒 . Also, Palladium (𝑃𝑑) can added to Gd to form 𝐺𝑑7𝑃𝑑3,

which has a higher Curie point than pure 𝐺𝑑. These 𝐺𝑑 alloys

exhibit magnetocaloric properties similar to pure 𝐺𝑑 [15]. At

least one family of alloys might be much better refrigerants

and can be used to construct a layered regenerator bed than the

prototype 𝐺𝑑 metal magnetic refrigerant because of the much

larger MCE.

B1.b Giant Magnetocaloric Effect Material (GMCE):-

A few years later, several other families of materials have

been shown exhibit the phrase "the giant magnetocaloric effect

'' materials at temperatures close to ambient. It has been well

established that the GMCE arises from magnetic field–induced

magnetostructural first-order transformations, [8]. Thus, 𝛥𝑆𝑀

for a GMCE material may be twice or more as large as the

ordinary MCE of a substance which undergoes a second order

transition, exhibits hysteresis and time dependence may limit

the usefulness of the GMCE materials in magnetic

refrigeration. The discovery of the GMCE spurred a broad

international interest in the MCE, lead to the discovery of four

new families, members of which exhibit the giant

magnetocaloric effect, 𝑀𝑛(𝐴𝑠1−x𝑆𝑏𝑥), 𝑀𝑛𝐹𝑒(𝑃1−x𝐴𝑠𝑥),

𝐿𝑎(𝐹𝑒13−x𝑆𝑖𝑥)𝐻𝑧 and 𝑁𝑖~55𝑀𝑛~20𝐺𝑎25, [16].

C. Some theoretical Background

The temperature and magnetic field, of a MCM are highly

coupled over certain typically limited; operating ranges, this

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characteristic allows them to be used within energy conversion

systems [15]. From the 1𝑠𝑡 law of thermodynamics the change

in internal energy 𝑑𝑈 is defined as the sum of the changes in

heat 𝛿Q and work 𝛿W. Magnetocaloric materials, magnetic

field (µ0𝐻) and magnetic moment M, form the work term in

Eq. (2).

𝑑𝑈 = 𝛿Q- 𝛿W (1)

𝑑𝑈 = 𝑇. 𝑑𝑆 + (µ0H. 𝑑𝑀) (2)

When MCM is magnetized isothermally, the arrangement of

the spins causes the magnetic entropy to decrease, if the

hysteresis is neglected, in an adiabatic process. The total

entropy of a magnetic material, at constant pressure, is a

function of magnetic field strength and the absolute

temperature. It is a combination of three different entropies,

magnetic specific entropy (𝑆𝑚𝑎𝑔), results from the magnetic

spins in the material, lattice specific entropy (Slat), results from

vibrations in the lattice and electronic specific entropy (𝑆𝑒𝑙𝑒),

results from free electrons in the material [12],

𝑆𝑡𝑜𝑡(𝑇, 𝐻) = 𝑆𝑚𝑎𝑔(𝑇, 𝐻) + 𝑆𝑙𝑎𝑡(𝑇) + 𝑆𝑒𝑙𝑒(𝑇) (3)

The lattice and the electronic specific entropies are

independent of the magnetic field and depend only on the

temperature, whereas the magnetic specific entropy depends

on both the magnetic field and the temperature [11]. In order

to compensate the reduction of magnetic entropy, electric and

lattice entropies will increase which leads to the raise in

temperature. In a reversible process, once the magnetic field is

removed, the material returns to its initial temperature.

Therefore, under adiabatic conditions i.e.:

∆𝑆𝑡𝑜𝑡 = ∆𝑆𝑚𝑎𝑔 + ∆𝑆𝑙𝑎𝑡 + ∆𝑆𝑒𝑙𝑒 (4)

(∆𝑆𝑙𝑎𝑡 + ∆𝑆𝑒𝑙𝑒) = −∆𝑆𝑚𝑎𝑔 (5)

The 𝑀𝐶𝐸 for a given material is typically in terms of either an

isothermal magnetic entropy change (𝛥𝑆𝑀) or an adiabatic

(isentropic, assuming no irreversible losses) temperature

change (𝛥𝑇𝑎𝑑), These two quantities describe the difference in

entropy or temperature, respectively, between two lines of

constant applied magnetic field on a temperature-specific

entropy diagram [9], as shown in Fig. (2 & 3), and following

the expression:

∆𝑆𝑚𝑎𝑔 = 𝜇0 ∫ (𝜕𝑀

𝜕𝑇)

𝐻 𝑑𝐻

𝐻1

𝐻0

(6)

∆𝑇𝑎𝑑 = −𝜇0 ∫𝑇

𝑐𝐻 (

𝜕𝑀

𝜕𝑇)

𝐻 𝑑𝐻

𝐻1

𝐻0

(7)

where, µ0 is the vacuum permeability of free space and M the

specific magnetization. H0 and Hi are the initial and the final

magnetic field strength, respectively; CH is the heat capacity in

constant magnetic field; and (𝜕𝑀

𝜕𝑇)

𝐻is the derivative of

magnetization with respect to temperature in a constant

magnetic field, [17]. Experimentally the Curie temperature

can be approximated by the temperature, at which the change

in magnetization,(𝜕𝑀

𝜕𝑇)

𝐻, be maximum, and also, ΔSM will be

maximized, as in Fig. (3).

Fig. (2): Temperature-volume specific entropy diagram of a typical

ferromagnetic material, Gd.

Fig. (3): Negative magnetic isothermal entropy change and adiabatic

temperature change as a function of temperature near the Curie temperature,

[14].

III.CRITERIA FOR SELECTING ROOM TEMPERATURE

MAGNETOCALORIC MATERIAL

On the basis of the corresponding theoretical analysis and the

nature of MCE, magnetic materials in MR should satisfy

several features for application, includes: [17], the assessment

of the suitability of these materials if largely rested upon

characterization of key thermodynamic properties such as

magnetic entropy change 𝛥𝑆𝑀, heat capacity, and adiabatic

temperature change 𝛥𝑇𝑎𝑑, thermal conductivity, large electric

resistance, high chemical stability and simple sample synthetic

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route. Issues such as hysteresis, cost, purity, ease of

regenerator manufacture, and relaxation rate all influence the

design and performance of AMR coolers [18].

IV.REVIEW IN SOME MAGNETOCALORIC MATERIALS RESEARCHES

To make magnetic refrigeration even more efficient, it is

necessary to find new materials with better MCE properties

than Gd. Substantial amount of work, research and the

development of materials over the past years have been a great

effort. Leading to discoveries of outstanding MCMs provided

new opportunities to use as alternative working materials in

AMRs at various temperatures [7]. Recently many materials

have been investigated, a brief summary of the known existing

near room temperature of magnetic refrigerant regenerator

materials reviewed over the few past years in following

researches.

Ref. [19] investigation experimentally of magnetocaloric and

magnetoresistive properties of a series of polycrystalline

Calcium and Surlium doped lanthanum manganite’s,

𝐿𝑎0.67𝐶𝑎0.33−𝑥𝑆𝑟𝑥𝑀𝑛𝑂3 (0 ≤ 𝑥 ≤ 0.33). The samples

consisted of sintered oxide powders prepared the glycine-

nitrate combustion technique. The compounds were

ferromagnetic and showed a Curie transition in the

temperature range 267– 370𝐾 (𝑇𝑐𝑢𝑖𝑟𝑒 increased with

increasing 𝑥). An analysis of the structural properties was

carried out by means of 𝑋 − 𝑟𝑎𝑦 diffraction and the Riveted

technique. The resistivity contribution arising from the

presence of grain boundaries increased with increasing 𝑆𝑟

content. Reducing the sintering temperature also enhanced the

grain boundary effects. The samples with low 𝑆𝑟 content

showed colossal magneto resistance (CMR) near room

temperature (~20 − 45 %, with µ0𝐻 = 0.8 𝑇). The CMR

effect was negligible for the samples with high 𝑆𝑟 content.

However, these samples exhibited a grain boundary-related

magnetoresistance at room temperature.

Ref. [14] studied and compared behaviors of the different

families of magnetic materials which exhibit large or unusual

MCE values. These families include: the 𝑙𝑎𝑛𝑡ℎ𝑎𝑛𝑖𝑑𝑒 Laves

phases (𝑅𝑀2), (𝑅 = 𝑙𝑎𝑛𝑡ℎ𝑎𝑛𝑖𝑑𝑒 & 𝑀 = 𝐴𝑙, 𝐶𝑜 𝑎𝑛𝑑 𝑁𝑖), 𝐺𝑑5(𝑆𝑖1−𝑥𝐺𝑒𝑋)4, 𝑀𝑛(𝐴𝑠1−x𝑆𝑏𝑥), 𝑀𝑛𝐹𝑒(𝑃1−x𝐴𝑠𝑥),

𝐿𝑎(𝐹𝑒13−x𝑆𝑖𝑥)𝐻𝑧 and their hydrides and the manganites

(𝑅1−𝑥𝑀𝑥𝑀𝑛𝑂3), where (M = Ca, Sr and Ba). The potential

for use of these materials in magnetic refrigeration was

discussed, including a comparison with Gd as a near room

temperature AMR material. A number of new materials with

GMCE properties have been compered and proposed as viable

magnetic refrigerants. However, conclusion was that no clear

winner as a replacement for 𝐺𝑑 metal, the prototype

298𝐾 magnetic refrigerant material. As of today, 𝐺𝑑 and 𝐺𝑑-

based solid solution alloys are still the materials of choice.

Ref. [10] investigated experimentally an active magnetic

regenerator cycle near room temperature to produced

significant temperature spans with relatively low applied

fields. Experimental results focused on multi-material, layered

regenerators, 𝑇𝑠𝑝𝑎𝑛 for regenerators composed made of two

different alloys 𝐺𝑑, 𝐺𝑑0.74𝑇𝑏0.26 and 𝐺𝑑0.85𝐸𝑟0.15. Using

composed AMRs of more than one material at magnetic field

strengths of 2𝑇 and cycle frequencies of 0.65 𝐻𝑧 created a

significant results test for AMRs operating with hot reservoir

temperatures between 285 𝐾 and 312 𝐾, temperature span

over the equivalently sized single material regenerator,

suggesting also, that viable room-temperature devices using

permanent magnets may be possible.

Ref. [20] an existing rotating bed magnetic refrigerator was

used to test first order MCMs as well as a layered bed

containing MCMs with two different Curie temperatures

compared with results for single layer, second order MCMs.

Materials were tested over a range of flow rates, frequencies,

and temperatures with one first order MCM,

𝐺𝑑5(𝑆𝑖2.09𝐺𝑒1.91)4, showed that this particular material suffers

from hysteresis or other frequency dependent effects,

performance decreasing with increasing operating frequency.

While another first order MCM, 𝐿𝑎𝐹𝑒𝑆𝑖𝐻, did not exhibit the

same degree of hysteresis, appears to be very promising

magnetocaloric refrigerant.

On the other hand, a bed layered with pure 𝐺𝑑 and 𝐺𝑑 − 𝐸𝑟,

alloy clearly demonstrated the importance of layering. The

layered bed performed better than beds containing either of the

constituent MCMs alone, producing more cooling power and a

larger, 𝑇𝑠𝑝𝑎𝑛. Layering was critical to produce a useful 𝑇𝑠𝑝𝑎𝑛

with first order MCM’s and have the potential to greatly

improve the performance of magnetic refrigeration.

Ref. [21] investigated the magnetic behavior, magnetocaloric

effect, and refrigeration capacity of the 𝐺𝑑60𝐴𝑙10𝑀𝑛30

metallic glass containing 𝑛𝑎𝑛𝑜𝑐𝑟𝑦𝑠𝑡𝑎𝑙𝑙𝑖𝑡𝑒𝑠 of 𝐺𝑑. Found that

the temperature was dependence of the magnetization exhibits

multiple second-order magnetic transitions due to the

composite effect. The resulting magnetic entropy change and

adiabatic temperature change compared well with MCE of

known magnetic refrigerants. A high refrigeration capacity of

660𝐽/𝑘𝑔, a large operating temperature range around 150𝐾

and a soft magnetic behavior make this 𝑛𝑎𝑛𝑜𝑐𝑜𝑚𝑝𝑜𝑠𝑖𝑡𝑒𝑠 an

attractive candidate as magnetic refrigerants in a temperature

range where pure 𝐷𝑦𝑠𝑝𝑟𝑜𝑠𝑖𝑢𝑚 was the best material

currently available.

Ref. [22] studied and compared a sample of MCM with

nominal composition 𝐿𝑎(𝐹𝑒, 𝐶𝑜, 𝑆𝑖)13which has the 𝑁𝑎𝑍𝑛13

structure, fabricated using a powder metallurgical production

route that can be utilized for large scale production. The

nominal composition 𝐿𝑎(𝐹𝑒, 𝐶𝑜, 𝑆𝑖)13 presents a

ferromagnetic to paramagnetic transition with a 𝑇𝑐𝑢𝑖𝑟𝑒 =278.7𝐾. Isothermal magnetization curves were used to

determine the volumetric magnetic entropy change,

𝛥𝑆𝑀 (𝑚𝐽/𝑐𝑚3𝑘). The values found compared to 𝐺𝑑 and

found to be almost twice as large for a given field. Hysteresis

curves and thermomagnetic data show that a slight thermal

hysteresis of 2K was present, while no magnetic hysteresis

exists in this material. Therefore, several of the disadvantages

previously associated with 𝑁𝑎𝑍𝑛13-structured materials are

not present in 𝐿𝑎(𝐹𝑒, 𝐶𝑜, 𝑆𝑖)13materials produced by powder

metallurgy.

Ref. [23] studied, designed, and optimized a magnetic

refrigeration system to modeling a particularly cost-effective

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method. Two different models of a refrigerator bed, the

Continuous-Solid (CS) and Dispersion-Concentric (DC)

models were discussed. The former model was

computationally faster and has been used to perform the

optimal design of a multi layered composed bed of 𝐿𝑎𝐹𝑒𝑆𝑖𝐻,

with a sharp first order transition. The model of the system

was extended to include the effect of coatings on the

magnetocaloric particles in the bed. Such coatings are

desirable for the prevention of chemical interaction with the

heat transfer fluid, or for the formation of connected beds.

The latter model, while requiring significantly longer

computer time, was ideally suited for investigating the effects

of particle coatings on machine performance. Shown the

optimized 𝐿𝑎𝐹𝑒𝑆𝑖𝐻 design, plastic coatings of

5 𝑚𝑖𝑐𝑟𝑜𝑛 thickness significantly degrade performance,

suggesting that non-metallic coatings applied to form

connected beds, for example, should be substantially thinner.

Ref. [24], parallel plate AMR device using regenerators made

of three different types of MCMs were compares. The three

different intermetallic materials of the type, 𝐿𝑎(𝐹𝑒, 𝐶𝑜, 𝑆𝑖)13

and ceramic material of the type 𝐿𝑎0.67𝐶𝑎0.26, 𝑆𝑟0.07𝑀𝑛1.05𝑂3,

which is referred to 𝐿𝐶𝑆𝑀 compares with 𝐺𝑑. A technique

method to prevent corrosion of the 𝐿𝑎(𝐹𝑒, 𝐶𝑜, 𝑆𝑖)13 plates and

reduce thermal conduction losses through the regenerator

housing wall were also presents. The best performance was

achieved for a single-material 𝐺𝑑 regenerator. The maximum

no-load temperature span produced by the Gd AMR

was10.2℃. One of the two-material 𝐿𝑎(𝐹𝑒, 𝐶𝑜, 𝑆𝑖)13

regenerators demonstrated improved AMR performance over

a single-material AMR when the transition temperatures of the

materials were 13℃ and 16℃. The experiments show that it is

important to select the correct transition temperatures of each

material based on the heat transfer characteristics and cycle

parameters of the AMR where the material will be used. Using

a thin polymer coating of the, 𝐿𝑎(𝐹𝑒, 𝐶𝑜, 𝑆𝑖)13, plates was

shown to have a minor impact on AMR performance and

could be viable method to reduce corrosion in the AMR.

Ref. [25] measured the Magnetocaloric properties of 𝐺𝑑 and

three sample of 𝐿𝑎𝐹𝑒13−𝑥−𝑦𝐶𝑜𝑥𝑆𝑖𝑦, with different chemical

composition, (𝑥 = 0.86, 𝑦 = 1.08), (𝑥 = 0.94, 𝑦 = 1.01)

and (𝑥 = 0.97, 𝑦 = 1.07). The measurements were directly

compared in an internal field of 1 𝑇 the (−𝛥𝑆𝑀), was

6.2, 5.1 𝑎𝑛𝑑 5.0 𝐽/𝑘𝑔𝐾, the specific heat capacity was

910, 840 𝑎𝑛𝑑 835 𝐽/𝑘𝑔𝐾 and the adiabatic temperature

change was 2.3, 2.1 𝑎𝑛𝑑 2.1𝐾 for the three 𝐿𝑎𝐹𝑒𝐶𝑜𝑆𝑖 samples, respectively. The peak temperature changes of the

order of 1𝐾 depending on the property measured, but are

around 276, 286 𝑎𝑛𝑑 288𝐾 for the three samples

respectively. The corresponding values for all properties for

𝐺𝑑 are 3.1, 340 𝐽/𝑘𝑔𝐾, 3.3𝐾 and a peak temperature of

295 𝐾. Thus, 𝐿𝑎𝐹𝑒𝐶𝑜𝑆𝑖 has a large enough magnetocaloric

effect for practical application in magnetic refrigeration.

Ref. [26] studied the magnetic phase transition and the

magnetic entropy change in the polycrystalline

𝐿𝑎0.67𝐵𝑎0.33𝑀𝑛0.9𝐶𝑟0.1𝑂3 synthesized by measuring the

magnetization as a function of temperature. The maximum

magnetic entropy change, and the relative cooling power are

found to be, 4.20 𝐽 /𝑘𝑔. 𝑘 and 238 𝐽/ 𝑘𝑔, respectively for a

5𝑇 field change. The analysis of the field dependence of the

(𝛥𝑆𝑀)variation reveals power-law dependence and the

coupled order parameters at the transition temperature. The

field dependence of the relative (𝑅𝐶𝑃) has been also studied,

following a power law with an exponent value compatible

with theoretical predictions. The broad range of temperatures

in which advantageous values of (−𝛥𝑆𝑀), and (𝑅𝐶𝑃)

obtained make of 𝐿𝑎0.67𝐵𝑎0.33𝑀𝑛0.9𝐶𝑟0.1𝑂3a potential

candidate for room-temperature magnetic refrigeration.

Ref. [27] investigated and studied systematically the magnetic

and magnetocaloric properties of materials namely,

𝛽𝐶𝑜(𝑂𝐻)2 nanosheets, 𝐿𝑎0.8𝐶𝑒0.2𝐹𝑒11.4𝑆𝑖1.6𝐵𝑥 and

𝐿𝑎0.8𝐶𝑒0.2𝐹𝑒11.4𝑆𝑖1.6𝐵𝑥 compounds and 𝑀𝑛0.94𝑇𝑖0.06 𝐶𝑜𝐺𝑒

alloy in detail with their structural, demonstrated how boron

doping at high levels tunes the magnetic transition from 1𝑠𝑡 to

2𝑛𝑑 order. Reported that the synthesis of 𝛽𝐶𝑜(𝑂𝐻)2

nanosheets using microwave was assisted hydrothermal and

conventional chemical reaction methods. Additionally that the

nature of the magnetic phase transitions was reflected by the

magnetic hysteresis of ~ 3.7, 9, 5.7, 0.4 & 0.3 J/kg for 𝑥 =0.0, 𝑥 = 0.03, 0.06, 0.2 & 0.3,respectively.The hysteresis loss

decreases from, 131.5 𝑡𝑜 8.1 𝐽 𝑘𝑔−1, when 𝑥 increases from,

0 𝑡𝑜 0.3, while 𝛥𝑆𝑀 obtained for a field change of 0 – 5 𝑇,

varies from 19.6 to 15.9 𝐽 𝑘𝑔−1 𝑘−1. This also simultaneously

shifts the 𝑇𝑐𝑢𝑖𝑟𝑒 from 174 𝑡𝑜 184 𝐾 and significantly

improves the effective refrigerant capacity (𝑅𝐶𝑒𝑓𝑓) of the

material from, 164 𝑡𝑜 305 𝐽 𝑘𝑔−1.

Ref. [28] Four similar geometry regenerators with three

different materials, 𝑃𝑟0.65𝑆𝑟0.35𝑀𝑛𝑂3, 𝐿𝑎(𝐹𝑒𝐶𝑜)13−𝑥𝑆𝑖𝑥 and

Gd using a permanent magnet based device, investigated over

a wide range of fluidic and magnetic operating conditions.

However, since no thermal exchanger was used, the device

provides only non-load temperature spans. The work deals

with an analysis of the performance of the regenerators as a

function of their utilization ratio 𝑈, (i.e. working conditions

such as the mass flow rate and frequency). Then, an attempt

made to correlate the performance of regenerator with the

physical properties of these different materials. The results

discussed on the basis of usual non-dimensional numbers

characterizing the heat transfer phenomena taking place

between the working fluid and the solid. Shown that even with

a low, 𝛥𝑇𝑎𝑑, the oxide 𝑃𝑟0.65𝑆𝑟0.35𝑀𝑛𝑂3 provided interesting

results, and the layered regenerator presents a better efficiency

than the single layer.

Ref. [29], make comparison experimentally of different

parallel plate active magnetic regenerators with two different

groups of MCM. First, a 𝐺𝑑-based single-layered AMR was

tested and analyzed under different operating conditions. Next

step, three different multi-layered AMRs with different

compositions and different 𝑇𝑐𝑢𝑖𝑟𝑒 made from

𝐿𝑎𝐹𝑒13−𝑥−𝑦𝐶𝑜𝑥𝑆𝑖𝑦 materials constructed and tested. Seven,

four- and two-layered 𝐿𝑎-based AMRs were evaluated. The

measurements were performed with respect to the maximum

measured 𝑇𝑠𝑝𝑎𝑖𝑛under different operating conditions and the

cooling load under different, 𝑇𝑠𝑝𝑎𝑖𝑛. In order to find the

optimum operating temperature range the AMRs were further

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compared for different hot-side temperatures. The 𝐺𝑑-based

AMR produced a larger, 𝑇𝑠𝑝𝑎𝑖𝑛, especially at higher operating

frequencies and higher mass-flow rates. Among the multi-

layered 𝐿𝑎 − 𝐹𝑒 − 𝐶𝑜 − 𝑆𝑖 AMRs, the seven and four-layered

AMRs showed very similar characteristics, while the two-

layered AMR was much poorer.

Ref. [30] study and investigated a multi-layered 𝑀𝐶𝑀 packed

bed regenerator in order to optimize performance get

maximum 𝑇𝑠𝑝𝑎𝑖𝑛 or maximum efficiency are different,

simulate by a numerical model developed to this packed bed.

𝐺𝑑 with different 𝑇𝑐𝑢𝑖𝑟𝑒 and adjusted heat capacities are used

to do the theoretical optimization. The study shows that the

layer design to get maximum 𝑇𝑠𝑝𝑎𝑛is different form the layer

design for maximizing Carnot efficiency, 𝜂𝐶𝑎𝑟𝑛𝑜𝑡 . The

maximum 𝑇𝑠𝑝𝑎𝑛can be achieved by choosing the materials

which have the highest MCE in the working temperature

range, while the highest 𝜂𝐶𝑎𝑟𝑛𝑜𝑡 are achieved by choosing

materials with 𝑇𝐶𝑢𝑟𝑖𝑒 above the average layer temperature

during a cycle. The simulation results for a fixed heat sink

temperature of 308.15 𝐾 and cooling load of 8.4 𝑊 for

various MCMs selections and two different sets of patterns for

variations in flow rate and magnetic field are reported.

Ref. [31] studied a new performance test and preliminary

comparison of AMRs consisting of 𝐺𝑑 sintered monolithic

spheres with diameters ranging from,450 − 550 𝑚𝜇, to

similar spheres, sorted in the same size range from the same

batch and merely packed. Pressure drop was compared at

uniform temperature and at a range of heat rejection

temperatures and 𝑇𝑠𝑝𝑎𝑛. Performance is compared in terms of

𝑇𝑠𝑝𝑎𝑛 at a range of heat rejection temperatures (295 − 308 𝐾)

with cooling loads, 0 𝑎𝑛𝑑 10 𝑊. Results tests showing that

the sintered spheres display larger 𝑃𝑑𝑟𝑜𝑝 and inferior

performance. Where, the moderate increase of 𝑃𝑑𝑟𝑜𝑝 with the

sintered spheres, while temperature spans were consistently

2.5 − 5 𝐾 smaller. The reason of the lower performance is

still unanswered and is currently under investigation.

Ref. [32], A multi-layer active magnetic regenerator consisting

of Gd and 𝐺𝑑0.73𝑇𝑏0.27, studied and compared with AMR of

pure 𝐺𝑑, to improve the refrigeration performance at a larger

𝑇𝑠𝑝𝑎𝑛, which limited by single magnetocaloric material. The

experimental magnetocaloric properties adopted for a better

precision. Effects of 𝐺𝑑0.73𝑇𝑏0.27 content 𝜑 and fluid

flowrate, 𝑞𝑉 on refrigeration capacity, 𝑞𝑟𝑒𝑓,𝑉, and coefficient

of performance, with the hot and cold reservoir temperatures,

investigated, as well as temperature contours of fluid and solid

matrix discussed. The study demonstrates that the multi-layer

AMR improves the 𝑞𝑟𝑒𝑓,𝑉 and 𝐶𝑂𝑃 by ～167% and 57%

at 𝑇𝑠𝑝𝑎𝑛 = 28𝐾, respectively. Moreover, it is observed that

𝑞𝑟𝑒𝑓,𝑉 of multi-layer AMR has a convex variation tendency

with 𝜑, and the maximum at 𝑇𝐶 of 268𝐾 equals

874.7 𝑘𝑊/𝑚3. As a contrast, COP has two peaks, and the

optimal 𝜑 is almost independent of 𝑇𝐶 , while it decreases with

a rising 𝑇ℎ. In addition, current investigation indicates that

𝑞𝑟𝑒𝑓,𝑉 takes a lager value at a larger 𝑞𝑉, while a smaller 𝑞𝑉

facilitates a good COP.

Ref. [33] used materials with different Curie temperatures to

enhance the MCE along the active magnetic regenerator, and

to improve the temperature span and thermal performance.

The performance of multilayer AMRs composed of 𝐺𝑑 and

two 𝐺𝑑𝑥−1𝑌𝑥 alloys was evaluated. Results indicated that by

increasing number of layers, cooling capacity increases,

especially for larger 𝑇𝑠𝑝𝑎𝑛. Working with a system

temperature span of 15 𝐾, the optimized configuration of a

three-layer regenerator presented 26.2% increase in

performance compared to a single-layer regenerator. For a

𝑇𝑠𝑝𝑎𝑛= 20𝐾, the performance was approximately 47.3%

higher than single-layer regenerator. It concluded that, for the

operating conditions and 𝑇𝑐𝑢𝑖𝑟𝑒 used in this work, at least 50%

of Gd is necessary in the multilayer regenerator in order to

achieve the largest cooling capacities.

Ref. [34] focused on low cost, corrosion resistant, rare earth

free MCMs, structural of iron based (𝐹𝑒0.72𝐶𝑟0.28)3𝐴𝑙 alloys.

The arc melted buttons and melt spun ribbons possessed the

𝐿21, which represent (𝐹𝑒, 𝐴𝑙 & 𝐶𝑟) crystal structure and 𝐵2

represent (𝐹𝑒 & 𝐴𝑙), crystal structure, respectively. A notable

enhancement of 33% in isothermal entropy change, (−𝛥𝑆 𝑚)

and 25% increase in relative cooling power for the ribbons

compared to the buttons attributed to higher structural disorder

in the (𝐹𝑒– 𝐶𝑟) and (𝐹𝑒– 𝐴𝑙) sub-lattices of the 𝐵2 structure.

Both bulk and ribbon samples exhibited soft ferromagnetic

nature, negligible hysteresis, broad −𝛥𝑆𝑚 versus T and a

Curie temperature (bulk 𝑇𝐶 = 285 K, ribbon 𝑇𝐶 = 300 𝐾)

near room temperature, which are highly desirable for

magnetic cooling applications. Thus, (𝐹𝑒0.72𝐶𝑟0.28)3𝐴𝑙 alloys

exhibit good magnetocaloric properties, ease of availability of

the constituent elements, established manufacturing

techniques, low cost, soft ferromagnetic behavior, low

hysteresis, good corrosion resistance and good thermal

conductivity.

Ref. [35] investigated the partial substitution of 𝐶𝑜 in 𝑁𝑖 site

of (𝑁𝑖2.1−𝑥𝐶𝑜𝑥x)𝑀𝑛0.9𝐺𝑎 (𝑥 = 0, 0.04, 0.12 𝑎𝑛𝑑 0.2) Heusler

alloys, observed through structural, transport, magnetic and

magnetocaloric properties and at room temperature. Heusler

alloys exhibits two transformations, paramagnetic 𝑃𝑀, to

ferromagnetic 𝐹𝑀. The presence of martensite around FM

transition in 𝑥 = 0 and 0.04 samples exhibit first-order

transition, whereas, appearance of austenite around 𝐹𝑀

transition leads second-order nature for 𝑥 = 0.12 and 0.2

samples. The change in magnetic entropy (−∆𝑆𝑀) is

calculated using Maxwell’s relation for all four samples. The

(−∆𝑆𝑀𝑝𝑒𝑎𝑘) is obtained (2.8 𝐽/𝑘𝑔. 𝐾) for 𝑥 = 0.12 sample.

Further, critical behavior of 𝑥 = 0.12 composition has been

studied due to its second order nature of 𝐹𝑀 − 𝑃𝑀 transition.

The estimated values of critical exponents suggested mean-

field model, and hence suggested the presence of long-range

ferromagnetic nature.

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V.CONCLUSION

Magnetic cooling is an environmentally friendly, energy

efficient. Thermal management technology relying on the use

of the various metallic materials and new high performance

alloys named Magnetocaloric Materials (MCMs) as the

refrigerant. Where, temperature span and magnetic field

density highly coupled over a certain typically limited

operating ranges, allows them to be used within energy

conversion systems. Magnetocaloric energy conversion did

not reach yet market applications. The major obstacle of this

green technology is the cost of device, which mostly related to

the magnet and partly magnetocaloric materials. The

technology is still an emerging one, and still a few challenges

to face to make this technology commercially viable.

Magnetic refrigeration units will be a reality in the near future,

now it just a niche market, or a full-blown growth market, in

future view from now is difficult to predict. Either way this

technology will be an important market for the rare earth

industry. All these circumstances did not prevent the

researcher to provide alternatives and distinctive to optimize

the performance of an active magnetic regenerative system

use. The article presents a review size of the MCMs used in

magnetic refrigeration researcher's desire to improve their

environment by changing the reality of the MCMs currently

used. Seems Gadolinium still candidate as the truly a

benchmark magnetic refrigerant material that exhibits

excellent magnetocaloric properties at room temperature and

difficult to improve upon. Not surprisingly, the metal has

employed in each of the early demonstrations of near ambient

cooling by the MCE. Moreover, it represents a potential

alternative, to phase out vapor-compression by the application

of low temperature energy sources. Table (1) shows a

summary of the Magnetocaloric Materials researches papers

working Up-to-end of 2014.

Nomenclature

Symbol Quantity Units

A Alkaline earth cation, Ca+2,

Sr+2, Ba+2, Na+2, K+2, etc.

-

COP Coefficient of Performance -

CGC Conventional Gas Compression. -

Dy Dysprosium. -

FM, FMT Ferromagnetic, Ferromagnetic

transition.

-

FOT First-order transition -

Gd Gadolinium. -

GMCE Giant Magnetocaloric Effect. -

La Lanthanum. -

MC Magnetocaloric -

MCE Magnetocaloric Effect. -

MCM Magnetocaloric Materials. -

MR Magnetic Refrigeration. -

PM Paramagnetic. -

𝑃𝑑𝑟𝑜𝑝 Pressure drop -

R Rare-earth cation, La, Pr, Y,

Nd, etc.

-

RC or 𝑞𝑟𝑒𝑓,𝑉 Refrigeration Capacity. 𝐽/𝑘𝑔

RCP Relative Cooling Power. 𝐽 /𝑘𝑔. 𝑘

Su Surlium

T 𝑇𝑒𝑠𝑙𝑎 Magnetic field unit. T

𝑇𝐶 and 𝑇ℎ Hot & cold reservoir

temperatures. K or ℃

𝑇𝑐𝑢𝑖𝑟𝑒 or 𝑇𝑐 Curie Temperature. =

𝑇𝑠𝑝𝑎𝑛 Temperature Span. =

𝑄𝑙𝑜𝑎𝑑 Cooling loads. W

𝜂𝐶𝑎𝑟𝑛𝑜𝑡 Carnot efficiency. -

𝜑 Content -

𝑞𝑉 Fluid flowrate. 𝑘𝑊/𝑚3

𝜂 Efficiency. -

µ0𝐻 Magnetic field. Tesla

-ΔSM Magnetic Entropy change. 𝐽 /𝑘𝑔. 𝑘

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[26] Oumezzine, M., Pena, O., Kallel., S. and Oumezzine, M., “Crossover of

the magnetocaloric effect and its importance on the determination of

the critical behavior in the La0.67Ba0.33Mn0.9Cr0.1O3 perovskite

manganite”, University de Monastir, Tunisia, Journal of Alloys and

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[27] Shamba, P., “Tuning Phase Transitions and Magnetocaloric Properties

of Novel Materials for Magnetic Refrigeration”, PhD. Thesis,

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[28] Legait, U., Guillou, F., Kedous-Lebouc, A., Hardy, V. and Almanza,

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[29] Tušek, J., Kitanovski, A., Tomc, U., Favero, C., and Poredo, A.,

“Experimental comparison of multi-layered La-Fe-Co-Si and single-

layered Gd active magnetic regenerators for use in a room temperature

magnetic refrigerator”, University of Ljubljana, Faculty of Mechanical

Engineering, Slovenia, Elsevier, International Journal of Refrigeration,

Vol. 37, Pp 117-126, 2014.

[30] Behzad M., Björn P., "Optimization of layered regenerator of a

magnetic refrigeration device". Institute of Technology, School of

Industrial Engineering and Management, Department of Energy

Technology, Stockholm, Sweden. International Journal of

Refrigeration, 26 April 2015.

[31] Tura, A., Nielsen, K.K., Ngo Van Nong, Nini Pryds, Trevizoli, P.V.,

Christiaanse, T.V, Teyber, R., and Rowe, A., "Experimental

Performance Evaluation of Sintered Gd Spheres Packed Beds".,

University of Victoria, Victoria, BC, Canada, and Technical University

of Denmark, Roskilde, Denmark. Conference Paper. September, 2016.

[32] Yonghua, Y., Shen, Y, Yuqian,T., Xiaobing, L. and Suyi, H., “A

numerical study on the unsteady heat transfer in active regenerator with

multi-layer refrigerants of rotary magnetic refrigerator near room

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[33] Cararo, J.E., Lozano, J.A., Trevizoli, P.V., Teyber, R., Rowe, A.,

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[35] Arumugam, S., Devarajan, U., Esakki M. S., Sanjay S., Thiyagarajan,

R., Manivel R. M., Rama Ra, N.V., and Alok B., " Structural,

transport, magnetic, magnetocaloric properties and critical analysis of

Ni-Co-Mn-Ga Heusler alloys". Journal of Magnetism and Magnetic

Materials, July 2017.

Table (1): Summary of the Magnetocaloric Materials researches papers working Up-to-end of 2014.

Authors Year Magnetic material Investigated Results Parameters

Dinesen, [19]. 2004

lanthanum manganite’s,

𝐿𝑎0.67𝐶𝑎0.33−𝑥𝑆𝑟𝑥𝑀𝑛𝑂3

(0 ≤ 𝑥 ≤ 0.33).

Grain resistivity arising with increasing

Sr. 𝑇𝑐𝑢𝑖𝑟𝑒 increased with𝑥.

0.8 𝑇

𝑇𝑐𝑢𝑖𝑟𝑒 = 267– 370𝐾.

Gschneidner, et

al. [14]. 2005

lanthanide families Laves phases𝑅𝑀2

𝐺𝑑5(𝑆𝑖1−𝑥𝐺𝑒𝑋)4, 𝑀𝑛(𝐴𝑠1−x𝑆𝑏𝑥),

𝑀𝑛𝐹𝑒(𝑃1−x𝐴𝑠𝑥)

, 𝐿𝑎(𝐹𝑒13−x𝑆𝑖𝑥)𝐻𝑧, with 𝐺𝑑.

No clear winner can replaces Gd metal

near room temperature. 𝑇𝑐𝑢𝑖𝑟𝑒 = 298𝑘

Rowe, et al.

[10]. 2005

Multi-material layered AMR regenerators, of

two different alloys 𝐺𝑑, 𝐺𝑑0.74𝑇𝑏0.26 , &

𝐺𝑑0.85𝐸𝑟0.15.

Created a significant 𝑇𝑠𝑝𝑎𝑛 than single

material regenerator.

2𝑇 𝑓 = 0.65𝐻𝑧

𝑇ℎ = 285&312𝑘

Boeder and

Zimm, [20]. 2006

Compared two different 𝑇𝑐𝑢𝑖𝑟𝑒 FOMT

𝐺𝑑5(𝑆𝑖2.09𝐺𝑒1.91)4 Layered bed &

𝐿𝑎𝐹𝑒𝑆𝑖𝐻, with single SOMT bed,𝐺𝑑 &

𝐺𝑑 − 𝐸𝑟 alloy.

𝐺𝑑5(𝑆𝑖2.09𝐺𝑒1.91)4 suffer hysteresis &

performance decrees with increased

frequency. 𝐿𝑎𝐹𝑒𝑆𝑖𝐻, very promising.

1.5 𝑇𝑒𝑠𝑙𝑎

𝑓 = 5 𝐻𝑧

Gorsse, et al.

[21]. 2008

Magnetic behavior, MCE & RC of

𝐺𝑑60𝐴𝑙10𝑀𝑛30 metallic glass containing 𝐺𝑑

nanocrystallites.

nanocomposites attractive candidate &

pure Dy the best material currently

available.

𝑅𝐶 = 660𝐽/𝑘𝑔 𝑇 = 150𝐾.

International Journal of Computation and Applied Sciences IJOCAAS, Volume3, Issue 1, August 2017, ISSN: 2399-4509

200

200

Hansen, et al,

[22]. 2009

Compared powder metallurgy nominal

composition 𝐿𝑎(𝐹𝑒, 𝐶𝑜, 𝑆𝑖)13 & 𝑁𝑎𝑍𝑛13 structure materials.

𝐿𝑎(𝐹𝑒, 𝐶𝑜, 𝑆𝑖)13 presents Slight thermal

hysteresis of 2K. Corrode 𝑁𝑎𝑍𝑛13 in pure

water & no with 𝐿𝑎(𝐹𝑒, 𝐶𝑜, 𝑆𝑖)13.

𝑇𝑐𝑢𝑖𝑟𝑒 = 278.7𝐾

𝛥𝑆𝑀 = twice to

Gd.

Jacobs, et al.

[23]. 2010

Coatings bed on MC particles to prevention

of chemical interaction with the heat transfer

fluid.

Plastic coatings thickness5𝜇𝑚, decline 𝜂

with the COP dropping, 12%. . Suggested

thinner non-metallic best..

1.4 𝑇𝑒𝑠𝑙𝑎 𝑇𝑠𝑝𝑎𝑛 = 20℃,

Coated. 𝐶𝑃 = 25%

<uncoated.

Engelbrecht, et

al. [24]. 2010

3different intermetallic type,

𝐿𝑎(𝐹𝑒, 𝐶𝑜, 𝑆𝑖)13 & ceramic

𝐿𝑎0.67𝐶𝑎0.26, 𝑆𝑟0.07𝑀𝑛1.05𝑂3 Compared

with𝐺𝑑.

Gd best & polymer coating of

𝐿𝑎(𝐹𝑒, 𝐶𝑜, 𝑆𝑖)13, plates viable to reduce corrosion in the AMR.

𝑇𝑠𝑝𝑎𝑛 = 10.2℃

The 2 matrials

𝑇𝑡𝑟𝑎𝑛𝑠𝑖𝑜𝑛= 13 &16 ℃.

Bjφrk, et al.

[25]. 2010

𝐿𝑎𝐹𝑒13−𝑥−𝑦𝐶𝑜𝑥𝑆𝑖𝑦 3samples measured and

compared, to commercial grade Gd.

𝐿𝑎𝐹𝑒𝐶𝑜𝑆𝑖 has large MCE for practical

application in magnetic refrigeration.

1 𝑇

𝑇𝑝𝑒𝑎𝑘 = 276– 286&288𝑘

−𝛥𝑆𝑀 = 6.2 − 5.1

& 5.0 𝐽/𝑘𝑔 𝐾

Oumezzine, et

al. [26]. 2012

Polycrystalline 𝐿𝑎0.67𝐵𝑎0.33𝑀𝑛0.9𝐶𝑟0.1𝑂3

Synthesized.

𝐿𝑎0.67𝐵𝑎0.33𝑀𝑛0.9𝐶𝑟0.1𝑂3 Candidate for

MR near room temperature.

5 𝑇 −𝛥𝑆𝑀 = 4.20 𝐽/𝑘𝑔𝑘

𝑅𝐶𝑃 = 238 𝐽/𝑘𝑔

Shamba, [27]. 2013

Nanosheets 𝛽𝐶𝑜(𝑂𝐻)2 and,

𝐿𝑎0.8𝐶𝑒0.2𝐹𝑒11.4𝑆𝑖1.6𝐵𝑥 ,

𝐿𝑎0.8𝐶𝑒0.2𝐹𝑒11.4𝑆𝑖1.6𝐵𝑥 compounds & alloy

of 𝑀𝑛0.94𝑇𝑖0.06 𝐶𝑜𝐺𝑒.

Hysteresis loss decreases

from131.5 𝑡𝑜 8.1 𝐽 𝑘𝑔−1, when 𝑥

increases, 0 𝑡𝑜 0.3. shifts 𝑇𝑐𝑢𝑖𝑟𝑒& 𝑅𝐶𝑒𝑓𝑓

.Improves.

0 – 5 𝑇

−𝛥𝑆𝑀= 19.6 − 15.9 𝐽/𝑘𝑔𝑘

𝑇𝑐𝑢𝑖𝑟𝑒 = 174,184𝐾 𝑅𝐶𝑒𝑓𝑓= 164 −

305 𝐽 /𝑘𝑔

Legait, et al.

[28]. 2014

4 similar geometry regenerators with 3

different materials 𝑃𝑟0.65𝑆𝑟0.35𝑀𝑛𝑂3,

𝐿𝑎(𝐹𝑒𝐶𝑜)13−𝑥𝑆𝑖𝑥 and Gd.

Even 𝛥𝑇𝑎𝑑 low Oxide 𝑃𝑟0.65𝑆𝑟0.35𝑀𝑛𝑂3

provided interesting results & layered

regenerator better efficiency than single.

1.1 𝑇

𝛥𝑇𝑠𝑝𝑎𝑖𝑛 = 16𝑘,

𝛥𝑇𝑠𝑝𝑎𝑖𝑛 = 14𝑘,

for 𝐿𝑎𝐹𝑒𝑆𝑖𝐶𝑜& 𝐺𝑑,

respectively

Tušek, et al.

[29]. 2014

3 multi-layered compositions

𝐿𝑎𝐹𝑒13−𝑥−𝑦𝐶𝑜𝑥𝑆𝑖𝑦 have different 𝑇𝑐𝑢𝑖𝑟𝑒 &

𝐺𝑑 single-layered.

Gd- AMR produced a larger non-load

𝑇𝑠𝑝𝑎𝑛 among the multi-layered La-Fe-Co-

Si.

1.15 𝑇

𝑓 = 0.15 − 0.45𝐻𝑧

Behzad et al.

[30]. 2015

𝐺𝑑 different 𝑇𝑐𝑢𝑖𝑟𝑒 & adjusted heat

capacities, to get optimize regenerators of

MR for large 𝑇𝑠𝑝𝑎𝑛 or high efficiency, η.

Maximum 𝑇𝑠𝑝𝑎𝑛 achieved with highest

MCE, while highest 𝜂𝐶𝑎𝑟𝑛𝑜𝑡 with 𝑇𝐶𝑢𝑟𝑖𝑒

above average layer Temp.

𝑇𝑠𝑖𝑛𝑘 = 308.15𝑘

𝑄𝑙𝑜𝑎𝑑 = 8.4W

Tura, et al. [31]. 2016

Comparing 𝐺𝑑 sintered monolithic

spheres 𝐷 = 450 − 550 𝑚𝜇, to simply

packed spheres.

Display larger𝑃𝑑𝑟𝑜𝑝 inferior

performance, reason still unanswered

currently under investigation.

𝑇 = 295 − 308 𝐾

𝑇𝑠𝑝𝑎𝑛= 2.5 − 5K

𝑄𝑙𝑜𝑎𝑑 = 0 −10 𝑊 Smaller.

Yonghua, et al.

[32]. 2016

multi-layer Gd & 𝐺𝑑0.73𝑇𝑏0.27 compared with pure Gd, to improve the refrigeration

performance at a larger 𝑇𝑠𝑝𝑎𝑛.

COP has two peaks, and the optimal 𝜑 is

independent 𝑇𝐶 & decreases with rising

𝑇ℎ. multi-layer improves 𝑞𝑟𝑒𝑓,𝑉 and COP.

At 𝑇𝑠𝑝𝑎𝑛 =  28𝐾

𝑞𝑟𝑒𝑓,𝑉～167% &

COP ～57%.

Improves.

Cararo, et al.

[33]. 2016

Composed of Gd & two 𝐺𝑑𝑥−1𝑌𝑥 alloys with

different 𝑇𝑐𝑢𝑖𝑟𝑒 to improve 𝑇𝑠𝑝𝑎𝑛 & thermal

performance.

Increasing No. layers to 3 𝑇𝑠𝑝𝑎𝑛 =15K,

increase cooling capacity, & 𝑇𝑠𝑝𝑎𝑛 =20K,

performance.

𝑇𝑠𝑝𝑎𝑛 = 15 − 20K

𝑄𝑙𝑜𝑎𝑑 = 26.2% − 47.3%. higher with

3layer.

Sharma, et al.

[34]. 2017

Low cost, corrosion resistant

(𝐹𝑒0.72𝐶𝑟0.28)3𝐴𝑙 alloys, 𝐿21, (𝐹𝑒, 𝐴𝑙 & 𝐶𝑟)

& 𝐵2, (𝐹𝑒 & 𝐴𝑙), crystal structure.

(𝐹𝑒0.72𝐶𝑟0.28)3𝐴𝑙 Alloys possess

promising attributes for near room

temperature magnetic cooling use.

−ΔS m ～33%,

𝑅𝐶𝑃, 25%

𝑇𝐶 = 285 K, ribbon

300 𝐾

Arumugam, et

al. [35]. 2017

Structural, transport, magnetic,

magnetocaloric properties of the

(𝑁𝑖2,1−𝑥𝐶𝑜𝑥x)𝑀𝑛0.9𝐺𝑎 (𝑥 =0, 0.04, 0.12 & 0.2) Heusler alloys.

Martensite around FMT in 𝑥 = 0 & 0.04

exhibit FOT , while, appearance austenite

𝐹𝑀𝑇 leads SOT for 𝑥 = 0.12 & 0.2 samples.

𝑓𝑜𝑟 𝑥 = 0.12, 147 𝐾& 5 𝑇

Max. −∆𝑆𝑀𝑝𝑒𝑎𝑘

= 2.8 𝐽/𝑘𝑔. 𝐾