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International Journal of Computation and Applied Sciences IJOCAAS, Volume3, Issue 1, August 2017, ISSN: 2399-4509
192
192
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 [email protected]).
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
193
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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
International Journal of Computation and Applied Sciences IJOCAAS, Volume3, Issue 1, August 2017, ISSN: 2399-4509
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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
International Journal of Computation and Applied Sciences IJOCAAS, Volume3, Issue 1, August 2017, ISSN: 2399-4509
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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
International Journal of Computation and Applied Sciences IJOCAAS, Volume3, Issue 1, August 2017, ISSN: 2399-4509
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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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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