Search

There is an urgent demand for the development of new resource-saving and high-efficiency cryogenic refrigeration technologies against the historical backdrop of increasing scarcity of resources and energy. Magnetic refrigeration technology based on the magnetocaloric effect (MCE) of magnetic materials is a promising approach to address helium resource constraints and improve energy efficiency. Here, a brilliant cryogenic magnetic refrigerant with a large low-field MCE and excellent refrigeration performance is presented. Benefiting from the enhanced ferromagnetism and low saturation magnetic field, the peaks of magnetic entropy change, refrigeration capacity, and adiabatic temperature change of Eu(Ti,Nb,Zr)O3 compounds reach 19.6 J·kg−1·K−1, 87.6 J·kg−1, and 5.5 K, respectively, for a field change of 0−1 T. Magnetic refrigeration experiments on a Gifford‒McMahon (GM)/magnetic hybrid refrigerator further demonstrated that EuTi0.8375Nb0.0625Zr0.1O3 is an excellent magnetic refrigerant operating near the liquid helium temperature. An appropriate amount of this magnetic refrigerant can significantly improve the refrigeration performance of the hybrid refrigerator. The cooling power in hybrid refrigeration mode is improved by a maximum of 52% over that in pure GM/HoCu2 mode at 4.2 K and 0.5 Hz. In addition, the cooling efficiency at 4.2 K is more than 40% greater than that of the pure GM/HoCu2 refrigerator.

A lanthanide carboxylates cluster derived from 1,8-naphthalene dicarboxylate (NDC= 1,8 naphthalene dicarboxylate) and 1,10-phenanthroline (Phen) has been synthesized. The cluster of Sm(III) has been utilized for luminescence and magnetic refrigeration properties. Most interestingly, the auto immobilization of atmospheric carbon dioxide forms carbonate ion which acts as a bridging ligand and is positioned at the middle of the cluster. This cluster is characterized by different spectroscopic tools like FT-IR, photoluminescence spectrum, and the molecular structure [Sm4(NDC)5(Phen)4(µ4-CO3)(H2O)3].3H2O.CH3OH (1) is determined by single crystals X-ray diffraction. π-conjugated ligand (NDC=1,8-Naphthalene dicarboxylate; Phen=phenanthroline) affects both absorption and photoluminescence intensity. Moreover, from the χmT vs temperature plot, it is observed that there is an occurrence of antiferromagnetic interaction among the SmIII centers. The cluster possesses high magnetocaloric value at low temperature which offers itself as a potential candidate for cryogenic molecular magnetic refrigerant material. In addition, thermogravimetric analysis, Hirsh field surface area analysis, and the optical diffuse reflectance spectrum of this cluster is also described. The synthesis, characterization, and magnetic properties of the Samarium cluster are described. The cluster is formed by the capturing of atmospheric CO2 in the form of carbonate ions which connects all four metal centers. The cluster exhibits a high magnetocaloric effect for which it can be used for molecular magnetic refrigerant material. Besides this, it can be a potential candidate for luminescent materials. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Refrigeration is the property of Journal of Refrigeration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Herein, as the fabrication of the microchannels for fluid flow using La(Fe,Si)13 magnetic refrigerant material is required while maintaining its superior magnetocaloric performance, sinter molding of the microchannel-designed La(Fe,Si)13 was investigated using a dissolutive mold comprised of NaCl to develop a molding process without contamination by carbon and other light elements. In addition, to avoid the thermal decomposition of fine particles of La(Fe,Si)13, a solid-state reaction was conducted during sintering using a mixture of α-Fe and La-rich compounds as the initial powder. After sintering, the sample shape exhibited channel widths and depths of 200 μm and pillar widths of 300 μm, which were originally designed for the NaCl dissolutive mold. The metallographic microstructure mostly comprised the La(Fe,Si)13 phase, and the volume fractions of the extra phases, such as α-Fe and La2O3, were suppressed to 1.1 % and 3.2 %, respectively. The maximum of the magnetic entropy change in a single pillar reached −19 J/kg K. Direct observation of magnetic nucleation/growth confirmed the smooth emergence of the first-order transitions in multiple pillars. Consequently, this fabrication approach promoted micro-channel-designed La(Fe,Si)13Hy while maintaining a large magnetocaloric effect via low carbon contamination.

Two structurally dissimilar 3d-4f cages having the formulae [(CoIII)3Gd4(μ3-OH)2(CO3) (O2CtBu)11(teaH)3]·5H2O (1) and [(CoIII)3Dy3(μ3-OH)4(O2CtBu)6(teaH)3]·(NO3)2·H2O (2) have been isolated under similar reaction conditions and stoichiometry of the reactants. The most important factor for structural diversity seems to be the incorporation of one μ3-carbonate anion in 1 and not in 2. Co atoms are in a +3 oxidation state in both complexes, as shown by the Bond Valence Sum (BVS) calculations and bond lengths, and as further supported by magnetic measurements. Co3Gd4 displays a significant magnetocaloric effect (−∆Sm = 25.67 J kg−1 K−1), and Co3Dy3 shows a single molecule magnet (SMM) behavior.

Magnetic properties, magnetocaloric effect, and critical behavior of Fe84-xCr2+xB2Co2Zr10 (x = 1, 2, 3, 4, 5, and 6) rapidly quenched alloy ribbons prepared by melt-spinning method have been investigated. X-ray diffraction analysis shows that the ribbons are almost amorphous. All the ribbons exhibit soft magnetic behavior with a low coercivity, Hc < 20 Oe. The magnetic phase transition temperature of the alloy can be adjusted in the room temperature region by appropriate Cr concentrations. With increasing Cr concentration, Curie temperature (TC) of the alloys is reduced from 330 K (for x = 1) to 290 K (for x = 6). The quite high maximum magnetic entropy change, |ΔSm|max > 0.8 J.kg−1.K−1 (under a magnetic field change of 12 kOe), and the wide working temperature range, δT > 90 K, around room temperature, have been achieved on these alloy ribbons. The obtained results reveal that Fe84-xCr2+xB2Co2Zr10 alloys are potential candidates for the magnetic refrigerants at room temperature region. Using the Arrott-Noakes method, critical analyses around the ferromagnetic-paramagnetic phase transition elucidated the magnetic orders in the alloys. The critical parameters determined for Fe84-xCr2+xB2Co2Zr10 ribbons are close to those of the mean-field theory applied for the long-range ferromagnetic orders. [ABSTRACT FROM AUTHOR]

The hydrogen absorption of the LaFe10.9Co0.8Si1.3 compound under constant 1.01 × 105 Pa H2 gas in a flow hydrogen atmosphere was studied. The effects of hydrogen absorption on structure, Curie temperature, phase transition and magnetic property were investigated by X-ray diffraction (XRD), differential scanning calorimeter (DSC) and superconducting quantum interference device, respectively. The hydrides of LaFe10.9Co0.8Si1.3 crystallize into NaZn13-type structural phase after hydrogen absorption at temperature from 548 to 623 K. Lower hydrogen absorption temperature is of no advantage for pure 1:13 phase formation in a flow H2 atmosphere. The Curie temperature (TC) of LaFe10.9Co0.8Si1.3 compound increases by 70 K or more after hydrogen absorption. For LaFe10.9Co0.8Si1.3H1.8 compound, the maximum magnetic entropy change and the relative cooling power under a magnetic field change of 0-2 T are 6.1 J·kg−1·K−1 and 170 J·kg−1, respectively. Large refrigerant capacity, low hysteresis loss and wide temperature span of magnetic entropy change peak make it a competitive practical candidate for magnetic refrigerant. [ABSTRACT FROM AUTHOR]

A metal-organic framework (MOF) based on gadolinium ion (Gd 3+ ) and tricarboxylate ligand, [Gd(BTPCA)(H 2 O)]·2DMF·3H 2 O ( Gd-BTPCA ) (H 3 BTPCA =1,1′,1′-(benzene-1,3,5-triyl)tripiperidine-4-carboxylic acid; DMF=dimethylformamide), was synthesized and structurally characterized. The adjacent Gd 3+ ions are intraconnected by the carboxylate groups of the BTPCA 3- ligands to form a 1D Gd 3+ ion chain. The 1D Gd 3+ ion chains are interconnected by the BTPCA 3- ligands, giving rise to a 3D framework with 1D open channel. The magnetic studies indicate that Gd-BTPCA exhibits weak ferromagnetic interactions, and acts as a cryogenic magnetic refrigerant having the magnetic entropy change (−Δ S m ) of 20.40 J kg −1 K −1 for ΔH =7 T at 3 K. [ABSTRACT FROM AUTHOR]

The parent La 0.8 Ce 0.2 Fe 11.47 Mn 0.23 Si 1.3 were prepared by induction furnace and annealed at 1363 K for 144 h, then milled to powder and hot pressed into cylindrical block at723 K, 873 K, 1023 K and 1173 K respectively under the pressure of 30Mpa for 15min. The hot pressing samples were cut into thin plates and hydrogenated. The structure and morphology were tested by XRD and SEM method, the magnetic property were tested by VSM. The experimental results show that the structure of sample is more compact and the magnetocaloric effects increase with the increase of the hot pressing temperature. The max magnetic-entropy change ΔS M is 10.99 J/kgK (66.53 mJ/cm 3 K), max adiabatic temperature change ΔT ad is 2.5 K under a magnetic field change of 1.5 T for the sample hot pressed at 1173 K. The max bending strength is 113.6 Mpa and the thermal conductivity is 7.3w/mk. [ABSTRACT FROM AUTHOR]

This paper presents the structure, magnetic properties, and magnetocaloric effect of the polycrystalline compound GdNiAl 2 . Powder X-ray diffraction (XRD) measurement and Rietveld refinement revealed that GdNiAl 2 alloy is CuMgAl 2 -type phase structure with about 1 wt% GdNi 2 Al 3 secondary phase. Magnetic measurements suggest that the compound is ferromagnetic and undergoes a second-order phase transition near 28 K. The maximum value of magnetic entropy change reaches 16.0 J/kg K for an applied magnetic field change of 0–50 kOe and the relative cooling power was 6.4×10 2 J/kg. It is a promising candidate as a magnetocaloric material working near liquid hydrogen temperature (~20 K) exhibiting large relative cooling power. [ABSTRACT FROM AUTHOR]

[Display omitted] • A submillimeter-scale microchannel/pillar structure composed of La(Fe,Si) 13 compound was fabricated by reactive sintering using an NaCl mold. • Strong first-order magnetic transition was observed in the sintered structures, resulting in a magnetic entropy change of −19 J/kg K. Herein, as the fabrication of the microchannels for fluid flow using La(Fe,Si) 13 magnetic refrigerant material is required while maintaining its superior magnetocaloric performance, sinter molding of the microchannel-designed La(Fe,Si) 13 was investigated using a dissolutive mold comprised of NaCl to develop a molding process without contamination by carbon and other light elements. In addition, to avoid the thermal decomposition of fine particles of La(Fe,Si) 13 , a solid-state reaction was conducted during sintering using a mixture of α-Fe and La-rich compounds as the initial powder. After sintering, the sample shape exhibited channel widths and depths of 200 μm and pillar widths of 300 μm, which were originally designed for the NaCl dissolutive mold. The metallographic microstructure mostly comprised the La(Fe,Si) 13 phase, and the volume fractions of the extra phases, such as α-Fe and La 2 O 3 , were suppressed to 1.1 % and 3.2 %, respectively. The maximum of the magnetic entropy change in a single pillar reached −19 J/kg K. Direct observation of magnetic nucleation/growth confirmed the smooth emergence of the first-order transitions in multiple pillars. Consequently, this fabrication approach promoted micro-channel-designed La(Fe,Si) 13 H y while maintaining a large magnetocaloric effect via low carbon contamination. [ABSTRACT FROM AUTHOR]

Highlights: [•] The single-phase formation process of La(Fe0.89Si0.11)13 was investigated. [•] The NaZn13-type single-phase is obtained by annealing for 300h at 1323K. [•] The Curie temperature is increased by annealing due to compositional homogenization. [•] The isothermal magnetic entropy change was related to the microstructure. [•] The peak position of the isothermal magnetic entropy change is affected by annealing. [Copyright &y& Elsevier]

The magnetocaloric properties of new complex magnetic material LaSrCuMnO, suitable for the Ericsson cycle, have been investigated. For this material, the effect of Cu doping can be attributed to a combination of doping disorder, Cu-Mn super exchange interactions and a site-percolation mechanism, which suppress the metallic conduction and Curie temperature. The Curie temperature decreases to 355 K. The magnetocaloric study exposes a comparable value of the magnetic entropy change for LaSrCuMnO sample, the value of the maximum entropy change, increases from 1.132 J/kgK to 3.11 J/kgK as magnetic field increases from 1 T to 4 T. A large relative cooling power ( RCP) has been observed for LaSrCuMnO As a result, the studied sample can be considered as potential material for magnetic refrigeration. [ABSTRACT FROM AUTHOR]

High field X-ray powder diffraction and magnetization measurements were carried out for MnFePGe in order to investigate the magnetic field effect on the structural property. A field-induced anisotropic lattice deformation was observed, accompanied by the metamagnetic transition from the paramagnetic to the ferromagnetic states in the vicinity of the Curie temperature of 285 K. In this deformation at 280 K, the lattice parameter a expands by 1.2 % whereas the parameter c contracts by 2.7 %. [ABSTRACT FROM AUTHOR]

Abstract: The magnetic entropy change in GdCo13−x Si x (x=3.8, 4, 4.1, and 4.2) intermetallic compounds has been investigated by means of magnetic measurements in the vicinity of their Curie temperature. It was found that the magnetic ordering temperatures decrease from 60K at x=3.8 to 28K for x=4.2. The magnetic entropy change is calculated from isothermal magnetization versus magnetic field at various temperatures using the Maxwell relation. As a result, the maximum magnetic entropy changes of the investigated compounds, at their Curie temperatures, decrease from 11.5J/kgK for x=4.2 to 6.86J/kg K for x=3.8 in a field change of 0–3T, whereas it decreases from 5.13J/kgK for x=4.2 to 2.60J/kgK for x=3.8 in a field change of 0–1T. Moreover, the maximum value of the magnetic entropy change obtained at a higher field for GdCo13−x Si x with x=4 (23.75J/kgK at 5T) is comparable to that of various types of compounds with a cubic NaZn13-type structure. Finally, the maximum of the magnetic entropy change is found to decrease with increasing Si content. [Copyright &y& Elsevier]

Abstract: The effect of Ti substitution on the magnetocaloric effect of the La0.70Sr0.30MnO3 perovskite was investigated. The magnetic entropy change (−ΔS M ) was deduced by two methods: a Maxwell relation and the Landau theory. The magnetocaloric data displays a large value of the magnetic entropy change (−ΔS M ) near the Curie temperature (T C =210K), which increases when increasing the applied magnetic field. A good agreement is found between the experimental (−ΔS M ) and the one estimated by Landau theory. The relative cooling power values vary from 49 to 288Jkg−1 upon variation of the applied magnetic field at 1 and 5T. Under 5T, the relative cooling power value for La0.70Sr0.30Mn0.90Ti0.10O3 is about 70% of the conventional refrigerant Gd material. As a result, the herein reported compound can be considered as a promising material in magnetic refrigeration technology. [Copyright &y& Elsevier]

Abstract: The maximum value of hysteresis loss E h MAX due to the itinerant-electron metamagnetic (IEM) transition of La(Fe x Si1− x )13 and the partially substituted compounds La1− z Ce z (Fe0.86Si0.14)13 and La1− z ′Pr z ′(Fe0.86Si0.14)13 increases when the magnetocaloric effects (MCEs) become large. It should be noted that the reduction of E h MAX without the decrease of large MCEs is achieved in La1− z Ce z (Fe0.86Si0.14)13 and La1− z ′Pr z ′(Fe0.86Si0.14)13. For both the compound systems mentioned above, the critical temperature T 0 for the IEM transition decreases and the difference between T 0 and the Curie temperature T C becomes larger with decreasing T C. These results are consistent with the magnetic phase diagram of La(Fe0.86Si0.14)13 under hydrostatic pressure. Consequently, the reduction of E h MAX in La1− z Ce z (Fe0.86Si0.14)13 and La1− z ′Pr z ′(Fe0.86Si0.14)13 is closely related with the magnetovolume effects. [Copyright &y& Elsevier]

Abstract: The crystalline structures, magnetic properties and magnetocaloric effect (MCE) of MnCo1− x Ge alloys (0.02⩽x⩽0.2) have been reported. The crystalline structures of MnCo1− x Ge (x⩽0.06) alloys are mainly of TiNiSi-type phase, and Ni2In-type structure dominates for x>0.06. With decreasing Co concentrations the saturated magnetization of these compounds decreases. Large low-field magnetic entropy change −ΔSM of about 2.3J/kgK in MnCo0.94Ge alloy has been obtained for a magnetic field change of 1T. Moreover, it is found that TiNiSi-type phase exhibits larger −ΔSM than Ni2In-type one. For MnCo0.94Ge alloy, considerable low-field refrigerant capacity (RC) (∼460mJ/cm3), low coercivity and easy synthesis make these alloys potential candidates for near-room temperature magnetic refrigerants. [Copyright &y& Elsevier]

Abstract: The influence of Dy on the magnetocaloric effect in Gd0.97− x Dy x V0.03 (x =0.1, 0.2, 0.3) alloys has been studied. These alloys were prepared by arc melting on a water-cooled copper hearth under an argon atmosphere. The magnetization behavior has been analyzed by X-ray diffraction and a vibrating sample magnetometer. Results indicate that the Curie points of Gd0.97− x Dy x V0.03 alloys decrease linearly with increasing content of Dy. The values of maximum magnetic entropy change (ΔSM) and relative cooling power (RCP) for x =0∼0.2 is larger than that of Gd alone over a wider temperature range. The Gd0.97− x Dy x V0.03 alloys have promising potential as working substance candidates for magnetic refrigeration due to their tunable Curie temperature and the favorable properties of the magnetocaloric effect. [Copyright &y& Elsevier]

Two structurally dissimilar 3d-4f cages having the formulae [(CoIII)3Gd4(μ3-OH)2(CO3) (O2CtBu)11(teaH)3]·5H2O (1) and [(CoIII)3Dy3(μ3-OH)4(O2CtBu)6(teaH)3]·(NO3)2·H2O (2) have been isolated under similar reaction conditions and stoichiometry of the reactants. The most important factor for structural diversity seems to be the incorporation of one μ3-carbonate anion in 1 and not in 2. Co atoms are in a +3 oxidation state in both complexes, as shown by the Bond Valence Sum (BVS) calculations and bond lengths, and as further supported by magnetic measurements. Co3Gd4 displays a significant magnetocaloric effect (−∆Sm = 25.67 J kg−1 K−1), and Co3Dy3 shows a single molecule magnet (SMM) behavior. [ABSTRACT FROM AUTHOR]

Abstract: Polycrystalline samples of potassium doped lanthanum manganites having nanometric crystallite size have been synthesized by pyrophoric method. The Curie temperature (T C) of the prepared samples is found to be strongly dependent on K content and spans between 260 and 309K. Close to T C, large change in magnetic entropy has been observed in all the samples. The maximum magnetic entropy change observed for samples with different concentration of K, exhibits a linear dependence with the applied magnetic field. Adiabatic temperature change at T C at 1T also increases with K doping and attains a maximum of 2.1K for La0.85K0.15MnO3. Estimated relative cooling power of La1−x K x MnO3 compounds is nearly one-third of pure Gd. In addition to the tuneability of T C between 260 and 310K, higher chemical stability, lower eddy current heating and inexpensive preparation technique; the magnetic entropy change in La0.85K0.15MnO3 compound at 1T magnetic field is found to be 3.00J/kgK and is ∼89% to that known for the prototype magnetic refrigerant (pure Gd). Our result on magnetocaloric properties suggests that La1−x K x MnO3 compounds are attractive as a possible refrigerant for near room temperature magnetic refrigeration. [Copyright &y& Elsevier]

In this paper, we review our recent results on magnetic refrigerants MnAs_{1-x}Sb_{x} and MnFeAs_{0.5}P_{0.5} by powder X-ray diffraction measurements in fields up to 5 T and in the temperature range from 8 to 320 K. MnAs shows a first-ordered structural transition with the volume expansion of 2.1% accompanied by a metamagnetic transition, but MnAs_{0.9}Sb_{0.1} exhibits an isostructural transition with the volume expansion of 1.1%. The cell volume of MnFeAs_{0.5}P_{0.5} slightly (-0.4%) and continuously decreases with increasing a magnetic field through the metamagnetic transition. [ABSTRACT FROM AUTHOR]

Abstract: The series of strontium-substituted calcium La0.5Ca0.5−x Sr x MnO3 has been studied and show the effect of strontium substitution. Magnetic studies on La0.5Ca0.5−x Sr x MnO3 compounds are reported. The substitution of a bigger cation, Sr2+ for Ca2+ enhances the Curie temperature (T C) from 228K (x =0) to 335K (x =0.5) and we have found a value of T C around room temperature (273K) for x =0.15. Maximum magnetic-entropy change (ΔS M) and relative cooling power (RCP) are discussed for La0.5Ca0.35Sr0.15MnO3 compound. The magnetic-entropy change is ∼0.615J/(kgK) at T C (273K) for a magnetic field of 2T and the RCP is 36.5J/kg, which suggests La0.5Ca0.35Sr0.15MnO3 compound a possible candidate for magnetic refrigerants near room temperature. [Copyright &y& Elsevier]

Abstract: The rare earth mononitride, ErN, has been synthesized by the carbothermic reduction and hot isostatic press methods. The magnetocaloric effect of ErN has been evaluated by calculating the magnetic entropy changes, ΔS, from the magnetization data sets and from the heat capacity measured at various temperatures and applied fields. The two results are in good agreement with each other. The ΔS value of ErN is the highest at 7.5K and higher than that of ErNi2 reported as the candidate material for the magnetic refrigerant of cryogenic technology. Heat capacity curve against temperature of ErN has a peak at 4.4K at zero-field. The peak value of the heat capacity of ErN is 507kJK−1 m−3. This value is larger than those of Er3Ni used commercially as a magnetic regenerator for the Gifford–McMahon refrigerator. The present results indicate that ErN is a promising material for the magnetic refrigerant and regenerator of cooling systems working above the boiling temperature of helium. [Copyright &y& Elsevier]

Abstract: We have synthesized Gd x Tb1−x N and Tb x Ho1−x N (x =0, 0.25, 0.5, 0.75 and 1) by the carbothermic reduction performed in a nitrogen gas stream. GdN and TbN have been completely miscible with each other as well as TbN and HoN. As x was changed from 0 to 1, the Curie temperature increased monotonously from 18.5 to 43.8K for Tb x Ho1−x N and from 43.8 to 61.2K for Gd x Tb1−x N. The magnetocaloric effects have been evaluated by calculating the magnetic entropy changes from the magnetization data sets measured at different applied fields and temperatures. In any composition x, the magnetocaloric effects of Gd x Tb1−x N and Tb x Ho1−x N are larger than those of Gd x Dy1−x N. Therefore, Gd x Tb1−x N and Tb x Ho1−x N are promising magnetic refrigerant materials for hydrogen liquefying system working below liquid nitrogen temperature. [Copyright &y& Elsevier]

Abstract: To obtain large magnetocaloric effects (MCEs) due to the itinerant-electron metamagnetic (IEM) transition in , the Curie temperature has been controlled by hydrogen absorption. In compounds,  K for increases with increasing hydrogen concentration, resulting in  K for . Furthermore, the magnetic moment is also stabilized against temperature by hydrogen absorption. Since the IEM transition is preserved after hydrogenation, large MCEs of the magnetic entropy change and the adiabatic temperature change have been observed around room temperature. A large value of has been confirmed by a direct measurement in adiabatic magnetic field change for the ( and 1.6). Consequently, the compounds and their hydrides are promising as high-performance magnetic refrigerants working in a wide range of temperature covering room temperature in relatively low applying magnetic fields. [Copyright &y& Elsevier]

The giant magnetocaloric effect Gd5Si2Ge2 alloy was prepared with 99wt% low purity commercial Gd. Powder XRD and magnetic measurements showed that the Gd5Si2Ge2 alloy annealed at 1200°C for 1 h had a significant magnetic- crystallographic first order phase transition at about 270 K. The maximal magnetic entropy change is 17.55 J · kg-1 · K-1 under a magnetic field change of 0-5 T. The distinct increase of magnetic entropy change belongs to the first-order phase transition from the orthorhombic Gd5Si4-type to the monoclinic Gd5Si2Ge2-type after high temperature heat-treatment. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of La0.67-xCa0.33MnO3 (x=0.00, 0.02, 0.06, and 0.10) with different La site vacancies have been prepared by the sol–gel method. The grain sizes of the samples are observed by SEM. XRD results show that the samples are single phase of perovskite-type oxides. The Curie temperatures and the magnetic entropy changes of the samples are measured on a vibrating sample magnetometer (VSM). The influence of the vacancy concentration in the La site on their magnetocaloric properties has been investigated. A large magnetic entropy change (∼2.78 J/kg K) is obtained in the sample La0.67-xCa0.33MnO3 (x=0.02) at its Curie temperature (277 K) in an applied magnetic field of 1 T. Results of magnetic measurement show that these materials with La site vacancies can be used as candidates for magnetic refrigerants near room temperature. [Copyright &y& Elsevier]

Abstract: A series of R2Fe17 (R=Sm, Gd, Tb, Dy, Er) have been synthesized. The magnetocaloric effect (MCE) of these compounds has been investigated by means of magnetic measurements in the vicinity of their Curie temperature. The Curie temperature of Er2Fe17 is 294K. The maximum magnetic entropy change of Er2Fe17 under 5T magnetic field is ∼3.68J/kgK. In the R2Fe17 (R=Sm, Gd, Tb, Dy, Er) system, the maximum magnetic entropy change under 1.5T magnetic field is 1.72, 0.89, 1.32, 1.59, 1.68J/kgK corresponding to their Curie temperature (400, 472, 415, 364, 294K), respectively. [Copyright &y& Elsevier]

Abstract: The thermally induced first-order magnetic phase transition in a La(Fe0.90Si0.10)13 compound has been observed at the Curie temperature T C by using Lorentz microscopy in the Fresnel mode. On heating the specimen, the magnetic domains instantly disappeared at T C due to the nature of the first-order phase transition. The coexistence of the ferromagnetic and paramagnetic phases was observed at T C. The magnetic domain structure below T C was unchanged by repeating the thermal cycles. This fact implies that the phase transition during thermal cycles does not induce any lattice defects that degrade the magnetocaloric effect. [Copyright &y& Elsevier]

Abstract: Magnetocaloric effects and magnetic properties of intermetallic compounds La(Fe1− x − y Co x Si y )13 with a cubic NaZn13-type structure have been investigated. By substituting Co for Fe or Si at Zn-site of La(Fe,Si)13, the value of Curie temperature T C increases with increasing Co content in all La(Fe1− x − y Co x Si y )13 systems (0

Two series of lanthanide complexes based on 4-chlorophenylacetic acid (HCPA), dinuclear [Ln 2 (CPA) 6 (DMF) 2 (H 2 O) 2 ] (Ln = Eu (1); Gd (2); Tb (3); Dy (4)) and one-dimensional (1D) linear [Ln 2 (CPA) 6 (H 2 O)] n (Ln = Eu (5); Gd (6); Tb (7); Dy (8)), were prepared, which are sensitive to the pH value. The dinuclear structure can be obtained when the pH value was controlled to be about 4.2, while the 1D structure can be formed when the pH value is ca. 5.1. The structure transformation of the dinuclear to 1D analogue at different pH values indicates that the CPA− ligand has a better affinity to replace the H 2 O/DMF molecule to bridge the neighboring Ln3+ ions to form the 1D structure at a higher pH value (∼5.1). The magnetic studies show that complexes 2 and 6 with isotropic Gd3+ ion display significant cryogenic magnetocaloric effect with a maximum −ΔS m value of 20.27 J kg−1 K−1 at 3 K and 7 T and 22.50 J kg−1 K−1 at 2 K and 7 T, respectively. Furthermore, the solid-state photophysical properties of 1 / 5 and 3 / 7 were studied and respectively exhibit strong characteristic emission peaks of Eu3+ and Tb3+ ions in the visible region, indicating that Eu- and Tb-based luminescences are sensitized effectively by the energy transfe from the ligand to the spin centers. Two series of dinuclear and 1D lanthanide complexes have been successfully prepared with HCPA, and are sensitive to pH value. The Gd-containing complexes display significant MCE, and the Eu- and Tb-based polymers exhibit strong characteristic lanthanide luminescence. Image 1 • Two series of lanthanide complexes were obtained solvothermally. • The dinuclear or 1D complexes are sensitive to the pH value. • The Gd-based complexes display significant MCE. • The Eu- and Tb-based complexes display characteristic Eu3+/Tb3+ luminescence. [ABSTRACT FROM AUTHOR]

Single-crystal X-ray diffraction analysis revealed that the central core of the cluster {ZnGd 12 } is unprecedented and composed of a beautiful structure built by two monocapped triangular prisms [ZnGd 6 sharing the ZnII vertex. Magnetic studies reveal that the magnetic field entropy of {ZnGd 12 } in a magnetic field of 7 T–2 T is 30.79 J kg−1 K−1. • A nanoscopic cluster {ZnGd 12 } have been synthesized based on ligand H 2 L. • The cluster {ZnGd 12 } has two monocapped triangular prisms [ZnGd 6 sharing ZnII vertices. • The −Δ S m of {ZnGd 12 } is 30.79 J kg−1 K−1. A novel tridecanuclear nanoscopic cluster {ZnGd 12 } have been synthesized by using the Schiff-base ligand, 2-methoxy-6-[(2-methylindole-2-carboxyl-1-ylidene) methyl]phenol (H 2 L), with zinc chloride and gadolinium nitrate in the presence of triethylamine as deprotonation reagent. Single-crystal X-ray diffraction analysis revealed that the central core of the cluster {ZnGd 12 } is unprecedented and composed of a beautiful structure built by two monocapped triangular prisms [ZnGd 6 sharing the ZnII vertex. Magnetic studies reveal that {ZnGd 12 } shows promise as a low-temperature magnetic refrigerant with the magnetic field entropy of 30.79 J kg−1 K−1 at a magnetic field of 7 T–2 T. [ABSTRACT FROM AUTHOR]