Maximum Magnetocaloric Effect Research Articles

Механический тепловой ключ криогенного магнитного рефрижератора

This work study the operating parameters of a cryogenic mechanical thermal switch, a detachable contact pair made of a alloy GdNi2 disk and a copper cylinder. The mechanical thermal switch operates in a vacuum in the temperature range of 8-325 K with a pressure of 250-350 kPa. The time of thermal equilibrium is studied at different contact areas with and without an indium thermal interface at an initial temperature difference of 0.8-10 K in the contact pair in the temperature range from 8 to 122 K. The temperature relaxation value is 33.7...39.9 seconds at a temperature difference of 3±0.14 K in the range of 50...122 K. Reducing the nominal contact area from 177 mm2 to 2.5 mm2 increases the temperature relaxation time at a temperature of 73.3 K from 36.6 to 63.5 seconds. This temperature range corresponds to the maximum magnetocaloric effect near the Curie temperature of the GdNi2 alloy. The values of the heat that must be removed to maintain the required temperature of the cooling object in a cryogenic magnetic refrigerator have been obtained.

Role of Gd3+ on the magnetocaloric properties of lanthanum-strontium manganite

In this work, the role of magnetic ion Gd3+ in the crystal structure, magnetic and magnetocaloric properties of doped lanthanum-strontium manganite (La0.7-xGdxSr0.3MnO3 varying x from 0 to 0.2) synthesized by high-energy ball milling assisted with annealing, is discussed. Furthermore, the interplay between the magnetic and crystal structure in co-doped manganites is proposed. The X-ray diffraction patterns confirm the complete formation of lanthanum manganite showing different crystal structures regarding the gadolinium content. The Sr2+/Gd3+ doped lanthanum manganites with Gd3+ concentration lower than 0.1 mol show rhombohedral crystal structure (R-3cH). Higher gadolinium concentrations promote a phase transition from rhombohedral to orthorhombic crystal structure. The Curie temperature of the manganites decreases with an increase in Gd3+ content, from 376 K to 257 K, for un-doped and x = 0.2 Gd3+, respectively, attributed to a weakening in the double exchange interaction. Close interaction of the lattice parameters such as bond distances, bond angles, and symmetry-related with the mixed magnetic interactions was observed. The maximum magnetocaloric effect (MCE) calculated using Maxwelĺs ratio was observed around the paramagnetic to ferromagnetic ordering, at 311 K, for gadolinium content of 0.15 mol, measured through the entropy change. The Sr2+/Gd3+ doped lanthanum manganite shows a magnetically induced entropy change (|ΔSM|) in the range from 2.4 to 3.69 Jkg-1K−1 under 18 kOe, for 0.10 and 0.15, respectively, doing this manganite a suitable material for refrigeration applications at room temperature.

Thermally Reduced Soft Magnetic CuFe Nanoparticles for High-Performance Electrical Devices

Developing economically soft magnetic materials for high-performance electrical devices is indispensable. Here, we present the structural and magnetic properties of thermally reduced soft CuFe nanoparticles. The fcc cubic structure of iron-rich Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">37</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">63</sub> and their composition was confirmed by Rietveld refinement. Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">37</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">63</sub> nanoparticles exhibited high saturation magnetization and coercivity of 127 emu/g (142 emu/g) and 4.3 Oe (31 Oe), respectively, at 300 K (5 K). They showed transitions at ~34 and ~249 K due to the Kondo temperature of CuFe and minor fraction of CuFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> , respectively. The exchange coupling between Cu and Fe was not significant, as demonstrated by field-cooled magnetization curves at 5 K. The magnetocaloric effect (MCE) in the range of fields and temperatures was estimated whereas the maximum MCE of -8.71 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> J.kg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> .K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> was achieved at 222 K. These soft magnetic materials, which exhibited stable high saturation magnetization with less heating effect during magnetization and demagnetization cycles, would be suitable candidates for magnetic applications.

Room temperature magneto-caloric effect and electron transport properties study on Ni2.14Mn0.55Sb1.31 alloy

Ni2.14Mnd0.55Sb1.3 Heusler alloy has been prepared by the conventional arc melting method with vacuum-sealed annealing. The sample has been crystallized to Fm3¯m space group in L21 phase, and it is the parent crystal structure of the Ni-based Full Heusler alloy. It has been found that the sample has the Curie temperature (para to ferromagnetic transition temperature) at 290K. It was determined from magnetization ∼ temperature plot (M ∼ T) as well as by employing the Arrott plot method. Also, critical exponent analysis by employing the Arrott plot and Kouvel-Fisher methods confirm that the sample (Ni2.14Mn0.55Sb1.31) obeys mean field theory with long range spin ordering. Analysis of temperature dependent resistivity data interestingly reveals the phonon-phonon and magnon-manon scattering dominance above and below the Curie temperature, respectively. The electrical and magnetic properties investigation endorse that there is a correlation between magnetic and electrical properties of the above sample. The magnetocaloric effect (MCE) analysis is carried out by using the Maxwell’s equations in isothermal magnetization data. It is interesting to note that the sample exhibits maximum MCE near the room temperature (∼290K), i.e., the magnetic Curie temperature. Hence the present alloy may be a potential material to be used for magnetic refrigeration application.

Magnetocaloric Effect of Micro- and Nanoparticles of Gd5Si4

Materials exhibiting a large magnetocaloric effect (MCE) at or near room temperature are critical for solid-state refrigeration applications. The MCE is described by a change in entropy (ΔSM) and/or temperature (ΔTad) of a material in response to a change in applied magnetic field. Ball milled materials generally exhibit smaller ΔSM values compared to bulk; however, milling broadens the effect, potentially increasing the relative cooling power (RCP). The as-cast Gd5Si4 is an attractive option due to its magnetic transition at 340 K and associated MCE. Investigation of effect of particles size and transition temperature in the binary material, Gd5Si4, can lead to development of functionally graded bulk material with higher MCE and RCP than the traditional bulk materials. A two-step ball-milling process, in which coarse powder of Gd5Si4 was first milled with poly(ethylene glycol) followed by milling in heptane was used to produce fine particles of Gd5Si4 that showed a broad distribution in particle size. Magnetic measurement on the milled sample obtained after washing with water show a decrease in Curie temperature and significant broadening of the magnetic transition. Compared to bulk Gd5Si4, the maximum MCE of the milled samples is also reduced and shifted down by close to 30 K, but the MCE remains substantial over a broader temperature range. The RCP of both milled samples increased 75% from the bulk material.

Improving the multicaloric properties of Pb(Fe0.5Nb0.5)O3 by controlling the sintering conditions and doping with manganese

Designing multicaloric single-phase materials with combined electro- and magnetocaloric effects is still at its initial stage and presents a number of challenges. One of the main challenges encountered so far is to reduce the excessive electrical conductivity, which leads to the appearance of Joule heating that might completely degrade the electrocaloric response. In this work, multicaloric Pb(Fe0.5Nb0.5)O3 material was successfully prepared exhibiting pronounced electrocaloric effect above room temperature and maximum magnetocaloric effect at cryogenic temperature. The conductivity was suppressed by controlling the sintering temperature. The ceramic sintered at 1000 °C exhibits maximum electrocaloric effective cooling of 0.88 °C at 28 °C and maximum magnetocaloric effect of 0.14 °C at −271 °C. The caloric properties can be further improved by doping Pb(Fe0.5Nb0.5)O3 with manganese. In comparison to the undoped sample, Pb(Fe0.5Nb0.5)O3 doped with 0.5 mol% of manganese exhibits three times higher maxima of electrocaloric effective cooling (2.47 °C at 80 °C) and magnetocaloric temperature change (0.44 °C at −271 °C).

Влияние изовалентного замещения катионов на термические, калорические и магнетокалорические свойства манганитов (La-=SUB=-1-y-=/SUB=-Eu-=SUB=-y-=/SUB=-)-=SUB=-0.7-=/SUB=-Pb-=SUB=-0.3-=/SUB=-MnO-=SUB=-3-=/SUB=-

AbstractCrystalline samples of the (La_1 – _ y Eu_ y )_0.7Pb_0.3MnO_3 ( y = 0, 0.2, 0.4, 0.5, 0.6, and 0.8) manganite solid solutions have been grown. Temperature dependences of the specific heat, thermal expansion, and high-intensity magnetocaloric effect have been investigated. A comparative analysis of the effect of isovalent cationic substitution on the thermal and caloric parameters of the ferromagnetic phase transition has been made. It has been shown that the growth of the Eu atom concentration leads to a decrease in the phase transition entropy and an increase in the baric coefficient dT / dp . Field and temperature dependences of the magnetocaloric effect have been established. It is demonstrated that, varying the ratio of cations, one can obtain the solid solutions with the maximum magnetocaloric effect value in fields of up to 6 kOe in a temperature range of 90–340 K. Owing to the similar reduced relative cooling powers, the investigated solid solutions can be used as reference solid-state cooling media in designing the cascade cooling systems.

Effect of Isovalent Cation Substitution on the Thermal, Caloric, and Magnetocaloric Properties of the (La1 – yEuy)0.7Pb0.3MnO3 Manganites

Crystalline samples of the (La1 – yEuy)0.7Pb0.3MnO3 (y = 0, 0.2, 0.4, 0.5, 0.6, and 0.8) manganite solid solutions have been grown. Temperature dependences of the specific heat, thermal expansion, and high-intensity magnetocaloric effect have been investigated. A comparative analysis of the effect of isovalent cationic substitution on the thermal and caloric parameters of the ferromagnetic phase transition has been made. It has been shown that the growth of the Eu atom concentration leads to a decrease in the phase transition entropy and an increase in the baric coefficient dT/dp. Field and temperature dependences of the magnetocaloric effect have been established. It is demonstrated that, varying the ratio of cations, one can obtain the solid solutions with the maximum magnetocaloric effect value in fields of up to 6 kOe in a temperature range of 90–340 K. Owing to the similar reduced relative cooling powers, the investigated solid solutions can be used as reference solid-state cooling media in designing the cascade cooling systems.

Magnetocaloric effect and piezoresponse of engineered ferroelectric-ferromagnetic heterostructures

Abstract This study reports the magnetocaloric effect (MCE) and piezoresponse of integrated ferroelectric-ferromagnetic heterostructures of PbZr0.52Ti0.48O3 (PZT) (5 nm)/Bi-Sr-Ca-Cu2-OX (BSCCO) (5 nm)/La0.67Sr0.33MnO3 (LSMO) (40 nm)/MgO (0 0 1). Magnetic and pizoresponse behavior of the heterostructures are found to be governed by magneto-electric coupling and induced lattice strains. In addition, a maximum MCE is studied using Maxwell equations from both Field Cooled (FC) and Zero Field Cooled (ZFC) magnetization data. Maximum MCE entropy change (|ΔS|) of 42.6 mJkg−1K−1 (at 258 K) and 41.7 mJkg−1K−1 (at 269 K) are found corresponding to FC and ZFC data, respectively. The variation in maximum entropy change and corresponding temperatures for FC and ZFC data revealed that the application of a magnetic field can significantly contribute towards tuning of the MCE. Interestingly, these multilayered structures are found to sustain MCE over a broad temperature range, which makes them attractive for improved solid-state energy conversion devices.

Persistent values of magnetocaloric effect in the multicomponent Laves phase compounds with varied composition

In this work we investigate the magnetocaloric effect (MCE) in the multicomponent RCo2-type compounds with a Laves phase structure varied by substitutions within both the rare earth (R) and Co sublattices. Complex substitutions increase dramatically the Curie temperatures at which the maximum MCE is observed. The Tbx(Dy0.5Ho0.5)1-xCo2 (0 ≤ x ≤ 0.5) compounds have transitions of the first order at the Curie temperature (TC) and exhibit a large magnetocaloric effect (with the adiabatic temperature change ΔTad as a measure of the effect) decreasing linearly from ΔTad = 3.6 K to 2.2 K (at μ0ΔH = 1.8 T) as x varies between 0 and 0.5. At the increasing Tb concentrations x above 0.5, the transition at TC in Tbx(Dy0.5Ho0.5)1-xCo2 changes order from first to the second while MCE remains constant ∼2.2 K. Volume magnetostriction is of the order of 1000 ppm in Tbx(Dy0.5Ho0.5)1-xCo2 in the vicinity of TC. Sets of compounds Tbx(Dy0.5Ho0.5)1-xCo1.75T0.25 (T = Fe, Al) having equal MCE values, appreciable magnetostrictive strains and continuously increased TC are found.

Magnetocaloric Effect in Ni50Mn36Sb14–xZ x (Z = Al, Ge; x = 0, 2) Heusler Alloys

The temperature dependences of the electrical resistivity and magnetization of the Ni50Mn36Sb14–xZ x (Z = Al, Ge; x = 0; 2) alloys have been used to determine the characteristic phase transition temperatures. The isothermal entropy change ΔS was determined using Maxwell’s equation and the field dependences of magnetization. The partial substitution of Ge for Sb has been shown to result in a slight increase in ΔS and a shift in the ΔS maximum to the low-temperature range. The substitution of Al for Sb leads to a decrease in the effect and shift in the ΔS maximum to the high-temperature range. It has been found that the maximum magnetocaloric effect has been observed for the Ni50Mn36Sb12Ge2 composition and is equal to ΔS = 1.3 J/(kg K) in a field change of 10 kOe.

Estimation of Curie temperature of manganite-based materials for magnetic refrigeration application using hybrid gravitational based support vector regression

Magnetic refrigeration (MR) technology stands a good chance of replacing the conventional gas compression system (CGCS) of refrigeration due to its unique features such as high efficiency, low cost as well as being environmental friendly. Its operation involves the use of magnetocaloric effect (MCE) of a magnetic material caused by application of magnetic field. Manganite-based material demonstrates maximum MCE at its magnetic ordering temperature known as Curie temperature (TC). Consequently, manganite-based material with TC around room temperature is essentially desired for effective utilization of this technology. The TC of manganite-based materials can be adequately altered to a desired value through doping with appropriate foreign materials. In order to determine a manganite with TC around room temperature and to circumvent experimental challenges therein, this work proposes a model that can effectively estimates the TC of manganite-based material doped with different materials with the aid of support vector regression (SVR) hybridized with gravitational search algorithm (GSA). Implementation of GSA algorithm ensures optimum selection of SVR hyper-parameters for improved performance of the developed model using lattice distortions as the descriptors. The result of the developed model is promising and agrees excellently with the experimental results. The outstanding estimates of the proposed model suggest its potential in promoting room temperature magnetic refrigeration through quick estimation of the effect of dopants on TC so as to obtain manganite that works well around the room temperature.

Magnetocaloric refrigerant with wide operating temperature range based on Mn5−xGe3(Co,Fe)x composite

The Curie temperature of Mn5Ge3 was raised or lowered by alloying the compound with Fe or Co; hence, the temperature at which maximum magnetocaloric effect manifested was easily manipulated by forming Mn5−xGe3(Co,Fe)x alloys to ultimately develop a composite magnetic refrigerant consisting of multiple Mn5Ge3 – based alloys. The composite refrigerant was designed to produce a table-like ΔSM–T curve and to maximize the RC value near room temperature. Linear combination of the ΔSM–T curves for the constituent materials showed that a composite composed of physical mixture of four different Mn5Ge3-based compounds: Mn5Ge3, Mn5.1Ge2.9, Mn4.75Co0.25Ge3 and Mn4.75Fe0.25Ge3, generated an optimal ΔSM–T curve with a table-like shape. The composite refrigerant with refrigeration capacity of 52Jkg−1, peak entropy change at 300K, and operating temperature range of 45K under ΔH=10kOe was suitable for room-temperature magnetic refrigeration. Moreover, by changing the relative fraction of each constituent material in the composite, it was shown that the operating temperature range could be fine-tuned as needed. The calculated ΔSM–T curve for the composite refrigerant by linear combination reasonably well matched the experimental ΔSM–T curve estimated from the M–H curves of the composite refrigerant, suggesting that the simple linear combination of the experimental ΔSM–T curves can be used to predict the performance of the composite magnetic refrigerants whose MCE was originated from the second order magnetic transition. In conclusion, being rare-earth free and lacking thermal or magnetic hysteresis, the Mn5Ge3 – based composite can be a competitive candidate magnetic refrigerant material operating at room temperature in terms of both economy and reliability compared to the giant MCE materials such as Gd – based intermetallic compounds or Heusler alloys.

Large reversible room-temperature magnetocaloric effect in the Ba0.5Sr1.5Zn2Fe12O22-related hexaferrites

The magnetic and magnetocaloric effect (MCE) of Mg or Cu-doped Ba0.5Sr1.5Zn2Fe12O22 hexaferrites synthesized by the sol-gel method are investigated. The Ba0.5Sr1.5Zn2Fe12O22 shows a sharp paramagnetic to ferrimagnetic phase transition and a large conventional MCE at around room temperature. By the partial substitution of Zn with Mg or Cu, the magnetic transition temperature as well as the maximum MCE temperature can be tuned in the range of 300 and 375K while keeping the maximum MCE nearly unchanged, which are beneficial characteristics for their application as near room-temperature magnetic refrigerants. For Ba0.5Sr1.5Zn2Fe12O22, it is found that the maximum values of magnetic entropy change –ΔSM and relative cooling power (RCP) are 1.27J/kg K and 124J/kg for ΔH=4.4T, respectively. Given its advantages, such as large RCP, suitable working temperature, low-cost raw materials, easy to synthesize, and environment-friendly, the Ba0.5Sr1.5Zn2Fe12O22 related hexaferrites may be potential candidates for room-temperature magnetic refrigeration.

Optimizing the Curie temperature of pseudo-binary RxR'2-xFe17 (R,R' = rare earth) for magnetic refrigeration

Several pseudo-binary RxR'2-xFe17 alloys (with R = Y, Ce, Pr, Gd and Dy) were synthesized with rhombohedral Th2Zn17-type crystal structure determined from x-ray and neutron powder diffraction. The choice of compositions was done with the aim of tuning the Curie temperature (TC) in the 270 ± 20 K temperature range, in order to obtain the maximum magneto-caloric effect around room temperature. The investigated compounds exhibit broad isothermal magnetic entropy changes, ΔSM(T), with moderate values of the refrigerant capacity, even though the values of ΔSMPeak are relatively low compared with those of the R2Fe17 compounds with R = Pr or Nd. The reduction on the ΔSMPeak is explained in terms of the diminution in the saturation magnetization value. Furthermore, the ΔSM(T) curves exhibit a similar caret-like behavior, suggesting that the magneto-caloric effect is mainly governed by the Fe-sublattice. A single master curve for ΔSM/ΔSMPeak(T) under different values of the magnetic field change are obtained for each compound by rescaling of the temperature axis.

Experimental investigation of the effect of thermal hysteresis in first order material MnFe(P,As) applied in an AMR device

The magnetocaloric first order material MnFe(P,As) is a candidate for room temperature magnetic refrigeration. However, these materials have intrinsic hysteresis and the impact on the refrigeration performance has not yet been thoroughly investigated in the literature.Here, the magnetocaloric effect (MCE) and the thermal hysteresis are studied using vibrating sample magnetometry. The influence on actual refrigeration performance is investigated with an established active magnetic regenerator (AMR) test device (Bahl et al., 2008), utilizing a flat plate regenerator of a single Curie temperature material.We find that the MCE curves are shifted 1.5 K when comparing heating and cooling the material, while the maximum MCE remains constant. The width of the MCE curve peak is seen to increase 0.3 K when cooling compared to heating. These results are confirmed by experiments on the AMR test device.

Improvement of magnetocaloric properties of Gd-Ge-Si alloys by alloying with iron

The influence of annealing of Gd5 Ge2 Si2 Fex alloys at 1200°C and of alloying with various amount of iron on structure as well as thermal and magnetocaloric properties is investigated. It was found that annealing for 1 to 10 hours improves the entropy change, but reduces the temperature of maximum magnetocaloric effect by up to 50 K. Prolonged annealing of the Gd5 Ge2 Si2 alloy results in the decrease of entropy change due to the reduction of Gd5 Ge2 Si2 phase content. Addition of iron to the ternary alloy enhances the magnetocaloric effect, if x = 0.4 – 0.6, especially if alloying is combined with annealing at 1200°C: the peak value of the isothermal entropy change from 0 to 2 T increases from 3.5 to 11 J/kgK. Simultaneously, the temperature of maximum magnetocaloric effect drops to 250 K. The changes in magnetocaloric properties are related to the change in phase transformation from the second order for arc molten ternary alloy to first order in the case of annealed and/or alloyed with iron. The results of this study indicate that the minor addition of iron and heat treatment to Gd-Ge-Si alloys may be useful in improving the materials’ magnetocaloric properties..

Co–Ln Mixed-Metal Phosphonate Grids and Cages as Molecular Magnetic Refrigerants

The synthesis, structures, and magnetic properties of six families of cobalt-lanthanide mixed-metal phosphonate complexes are reported in this Article. These six families can be divided into two structural types: grids, where the metal centers lie in a single plane, and cages. The grids include [4 × 3] {Co(8)Ln(4)}, [3 × 3] {Co(4)Ln(6)}, and [2 × 2] {Co(4)Ln(2)} families and a [4 × 4] {Co(8)Ln(8)} family where the central 2 × 2 square is rotated with respect to the external square. The cages include {Co(6)Ln(8)} and {Co(8)Ln(2)} families. Magnetic studies have been performed for these compounds, and for each family, the maximum magnetocaloric effect (MCE) has been observed for the Ln = Gd derivative, with a smaller MCE for the compounds containing magnetically anisotropic 4f-ions. The resulting entropy changes of the gadolinium derivatives are (for 3 K and 7 T) 11.8 J kg(-1) K(-1) for {Co(8)Gd(2)}; 20.0 J kg(-1) K(-1) for {Co(4)Gd(2)}; 21.1 J kg(-1) K(-1) for {Co(8)Gd(4)}; 21.4 J kg(-1) K(-1) for {Co(8)Gd(8)}; 23.6 J kg(-1) K(-1) for {Co(4)Gd(6)}; and 28.6 J kg(-1) K(-1) for {Co(6)Gd(8)}, from which we can see these values are proportional to the percentage of the gadolinium in the core.

Pressure tuning the magnetocaloric effect in valence transition compound YbInCu4

We have obtained the magnetocaloric effect (MCE) in YbInCu4 under different pressures and magnetic fields. The MCE at the valence transition could be maximized using a combination of magnetic field and applied pressure. The maximum value of the MCE for ΔH=7 T showed significant changes with pressure and peaked at 6.6 kbar. The temperature of the maximum MCE occurs near the assumed Kondo temperature for this compound. Using differential scanning calorimetry, we found that the entropy associated with the valence transition is nearly reversible under heating and cooling.

Origin and tuning of the magnetocaloric effect in the magnetic refrigerantMn1.1Fe0.9(P0.8Ge0.2)

Neutron-diffraction and magnetization measurements have been carried out on a series of samples of the magnetorefrigerant ${\text{Mn}}_{1+y}{\text{Fe}}_{1\ensuremath{-}y}{\text{P}}_{1\ensuremath{-}x}{\text{Ge}}_{x}$. The data reveal that the ferromagnetic and paramagnetic phases correspond to two very distinct crystal structures, with the magnetic-entropy change as a function of magnetic field or temperature being directly controlled by the phase fraction of this first-order transition. By tuning the physical properties of this system we have achieved a magnetic-entropy change [magnetocaloric effect (MCE)] for the composition ${\text{Mn}}_{1.1}{\text{Fe}}_{0.9}{\text{P}}_{0.80}{\text{Ge}}_{0.20}$ that has a similar shape for both increasing and decreasing field, with the maximum MCE exceeding $74\text{ }\text{J}/\text{kg}\text{ }\text{K}$---substantially higher than the previous record. The diffraction results also reveal that there is a substantial variation in the Ge content in the samples which causes a distribution of transition temperatures that reduces the MCE. It therefore should be possible to improve the MCE to exceed $100\text{ }\text{J}/\text{kg}\text{ }\text{K}$ under optimal conditions.