•Three three-dimensional (3D) Ln2Co2 clusters were successfully synthesized.•Three clusters are assembled via butterfly-shaped Ln2Co2Na2(L)2(C2O4)2(H2O)4 frames.•Gd2Co2 shows the large -∆Sm values at ...2.0 K (31.17 J kg−1 K−1 at 7.0 T; 20.18 J kg−1 K−1 at 2.0 T).
The heterometallic 3d-4f clusters are being researched, for some time now, as being applicable to molecular magnetism. Especially, the Gd3+-containing multi-nuclear clusters attract wide study attention, on account of the significant magnetocaloric effect (MCE). Herein, three-dimensional (3D) 3d-4f heterometallic clusters are successfully gained via solvothermal conditions, formulated as {Ln2Co2Na2(L)2(C2O4)2(H2O)4·(H2O)2}n (abbreviated as Ln2Co2, Ln = Gd for 1; Ln = Tb for 2, and Ln = Dy for 3; L = ethylenediaminetetraacetic acid disodium salt). Structural analysis shows that Ln2Co2 clusters are mainly consistent of the Ln2Co2Na2(L)2(C2O4)2(H2O)4 metal frames, which are the asymmetric building units. Interestingly, Ln2Co2Na2(L)2(C2O4)2(H2O)4 metal frames can be constructed by one chain-shaped Ln2(C2O4)2, one Na2(H2O)2 dimer, and two CoL(H2O) units. Tree building units are connected to constitute 3D structure of Ln2Co2. In addition, the metal ions make Gd2Co2 exhibit the magnetic entropy change (-∆Sm = 31.17 J kg−1 K−1 at 2.0 K and 7.0 T) and ideal -∆Sm value at low-field condition (20.18 J kg−1 K−1 at 2.0 K and 2.0 T).
Three three-dimensional (3D) 3d-4f heterometallic clusters are successfully gained via solvothermal conditions, formulated as {Ln2Co2Na2(L)2(C2O4)2(H2O)4·(H2O)2}n (abbreviated as Ln2Co2, Ln = Gd, Tb or Dy). Structural analysis shows that the Ln2Co2 clusters are mainly consistent of the butterfly-shaped Ln2Co2Na2(L)2(C2O4)2(H2O)4 metal frames. In addition, Gd2Co2 exhibits the large MCE (-∆Sm = 31.17 J kg−1 K−1 at 2.0 K and 7.0 T) and ideal -∆Sm value at low-field condition (20.18 J kg−1 K−1 at 2.0 K and 2.0 T). Display omitted
The Ln0.67Sr0.33MnO3 (Ln=La, Pr and Nd) nanoparticles were prepared by using the sol–gel method. The structural and magnetic properties of the samples were investigated in detail. The X-ray ...diffraction (XRD) analyses indicate that the La-doped sample crystalizes in rhombohedral perovskite structure and the Pr-doped and Nd-doped samples are mainly composed of orthorhombic perovskite structure phase. The Curie temperature and saturation magnetization are lowered and the phase transition is broadened by the Pr and Nd substitutions when comparing with the La-doped sample. All the samples exhibit significant magnetocaloric effects in a wide temperature range. Under a field change from 0 to 5T, the maximum values of isothermal entropy change are found to be 2.49, 1.94 and 0.93J/kgK for the samples with Ln=La, Pr and Nd, respectively, and the corresponding values of relative cooling power reach 225, 265 and 246J/kg. The results suggest that those nanoparticles could be useful for magnetic refrigeration in a broad temperature range.
Magnetic refrigeration technology based on the magnetocaloric effect (MCE) of magnetic substances has been considered a prominent, energy‐efficient, and environmentally benign cooling method. ...Exploring suitable magnetic substances is a prerequisite for practical applications. A family of rare‐earth‐free magnetocaloric materials called Mn30Fe20−xCuxAl50 alloys is identified room‐temperature refrigeration, which are derived from the well‐known MnAl‐based permanent magnets. As expected from experimental and theoretical investigations, all of the Mn30Fe20−xCuxAl50 alloys are crystallized in a stable cubic CsCl‐type crystal structure, revealing a single second‐order type magnetic phase transition (MPT) with tunable MPT temperature. They also exhibit a large reversible MCE and good magnetocaloric performances in a wide temperature range. Crucially, these Mn30Fe20−xCuxAl50 alloys represent a rare case of magnetic materials belonging to a large family that can be fabricated from low‐price, earth‐abundant, and non‐toxic elements. They could provide new choices for practical room‐temperature magnetic refrigeration applications.
The achievement of good magnetocaloric performances is reported in the Mn30Fe20‐xCuxAl50 alloys with a stable cubic CsCl‐type structure which are derived from the family of MnAl‐based permanent magnets. These alloys represent a rare case of magnetocaloric materials that can be fabricated from low‐price, earth‐abundant, and non‐toxic elements, which could provide new choices for room‐temperature refrigeration.
•Hamiltonian of interacting spins calculated by the Handrich-Kobe approximation.•Amorphous systems with ferrimagnetism and high caloric potentials.•Magnetism, direct and inverse magnetocaloric ...effect, and magnetic refrigeration.
In this work we will investigate the magnetic and magnetocaloric properties in the amorphous alloys formed by the Gd55FexAl45−x series. From an experimental point of view, it has been reported that these systems have high values for refrigerant capacity, and interesting magnetocaloric properties associated with the ferrimagnetic order. We propose a theoretical model described by two coupled magnetic sublattices of localized spins in the presence of an applied magnetic field based on Handrich’s approximation to study these systems. Through this model, we calculate the magnetization and the isothermal entropy change as functions of the temperature under the applied magnetic field change. We will try to understand the role of substitution of Fe for Al in the characterization of magnetism and the magnetocaloric effect of these systems. In addition, the study is important to understand the physical mechanisms involved in the ferrimagnetic transitions of amorphous alloys.
The magnetic transition and magnetocaloric effect of R5(Si, Sn)3 (R = Pr, Nd) alloys have been investigated. The single phase with Cr5B3-type tetragonal structure is observed for x(y) ≤ 1 in ...Pr5Si3-xSnx and Nd5Si3-ySny alloys. The magnetic phase transition temperature of these alloys is elevated with increased the substitution amount. All phase transitions in these alloys are of second-order nature undergoing low-temperature ferromagnetism to high-temperature paramagnetism. For the field change of 7 T, the maximum of entropy change (− ΔSMmax) of 7.0 J/kgK and 4.4 J/kgK have been achieved in Pr5Si2Sn and Nd5Si2Sn alloys compared with 12.1 J/kgK and 4.3 J/kgK in Pr5Si3 and Nd5Si3 alloys. The relative cooling power (RCP) is enhanced to 359.2 J kg-1 and 382.4 J kg-1 in Pr5Si2Sn and Nd5Si2Sn alloys compared with 283.2 J kg-1 and 216.5 J kg-1 in Pr5Si3 and Nd5Si3 alloys. The excellent magnetocaloric properties suggest that R5(Si, Sn)3 (R = Pr, Nd) alloys could be the promising candidates for magnetic cooling.
•Magnetic and magnetocaloric properties in R5(Si, Sn)3 (R = Pr, Nd) are investigated.•Promising cryogenic magnetocaloric performances have been observed.•R5(Si, Sn)3 (R = Pr, Nd) compounds are considerable for magnetic refrigeration.
The magnetocaloric effect and its most straightforward application, magnetic refrigeration, are topics of current interest due to the potential improvement of energy efficiency of cooling and ...temperature control systems, in combination with other environmental benefits associated to a technology that does not rely on the compression/expansion of harmful gases. This review presents the fundamentals of the effect, the techniques for its measurement with consideration of possible artifacts found in the characterization of the samples, a comprehensive and comparative analysis of different magnetocaloric materials, as well as possible routes to improve their performance. An overview of the different magnetocaloric prototypes found in literature as well as alternative applications of the magnetocaloric effect for fundamental studies of phase transitions are also included.
Rare-earth-based oxides are gradually becoming a new research hotspot in cryogenic magnetic refrigeration due to their advantages in bulk preparation and application. Magnetic transition from AFM to ...FM in EuTiO3 provides an effective strategy for modulating magnetism and enhancing magnetocaloric effect (MCE) in this magnetic system. Herein the structure, magnetism, and MCE of a series of Ta-doped EuTiO3 perovskites were investigated in detail. A significant lattice expansion was achieved by partially substituting Ta for B-site Ti without altering the crystal configuration, which tailors the cryogenic magnetism and MCEs of these compounds. Lattice expansion enhances ferromagnetic coupling, weakens antiferromagnetic super-exchange, and promotes the AFM-FM transition in EuTiO3, which enhances the low-field MCEs. The phase transition temperature of the compound increases from 5.5 K to about 9.5 K with increasing Ta doping. The values of −ΔSMmax and RC of EuTi0.9375Ta0.0625O3 are 15.9 J kg−1 K−1and 67.8 J kg−1 under magnetic field change of 0–1 T, which are enhanced by 44.5% and 105.5% over EuTiO3, respectively. Although a decrease in the magnetic entropy change occurs with increasing Ta doping, the refrigerating capacity is improved due to the broadened temperature range. This work not only provides a strategy for tailoring magnetic phase transition and MCE of magnetocaloric materials, but also offers effective candidates for magnetic refrigeration over a wide temperature range.
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This review summarized recent research progresses on the in-situ synthesis of molecular magnetorefrigerant materials derived from organic ligands, metal ions and templates generated ...in-situ.
•In-situ synthetic strategy for the construction of molecular magnetorefrigerant materials has been reviewed.•Molecular magnetorefrigerant materials with ligands, metal ions and templates formed in-situ have been illustrated.•The influencing factors toward magnetocaloric effect of the molecular magnetorefrigerants are detail discussed.
Zero-dimensional cluster complexes and coordination polymers for magnetic refrigeration have attracted great interest in the last decade. In-situ synthesis is a widely-used method to assemble various molecular magnetorefrigerant materials derived from different types of ligands. This review focuses mainly on the synthesis, structure and magnetochemistry of molecular magnetorefrigerant materials via in-situ synthesis, with an emphasis on in-situ generation of ligands, metal ions and templates. The first section gives a brief discussion on molecular magnetorefrigerants and some important principles obtained from magneto–structural correlation. The in-situ synthetic strategy will also be referred to and elucidated in this part. The next three sections give overviews of the main results obtained by our group and other groups in recent years, which are, in-situ generated ligands, metal ions and templates in the synthesis of molecular magnetorefrigerant materials. Finally, the conclusions and perspectives of molecular magnetorefrigerant materials will be presented. Some of the trends could provide new insights for the further development of this promising area.
The coupling between structural and magnetic degrees of freedom is crucial for realization of interesting physical phenomena associated with magneto-structural transformations resembling ...austenite-to-martensite transitions. Despite substantial efforts in design and discovery of materials with strong magnetocaloric effects, a majority of viable candidates are composed of non-earth-abundant and toxic elements, while others involve challenging syntheses and post processing. Guided by advanced density functional theory calculations, we report a new family of compounds, i.e., Mn0.5Fe0.5NiSi1-xAlx x = 0.045–0.07 exhibiting a giant magnetocaloric effect (MCE) that is tunable near room temperature. Their MCE functionality arises from a distinct magneto-structural transformation between a paramagnetic hexagonal Ni2In-type phase and ferromagnetic orthorhombic TiNiSi-type phase that can be actuated by magnetic field and/or pressure. As the transition is sensitive to external hydrostatic pressure, the same materials should also exhibit a strong barocaloric response in addition to the giant MCE.
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