Magnetic Refrigeration Property Research Articles

Design of Excellent Mechanical Performances and Magnetic Refrigeration via In Situ Forming Dual-Phase Alloys.

Magnetic refrigeration technology can achieve higher energy efficiency based on the magnetocaloric effect (MCE). However, the practical application of MCE materials is hindered by their poor mechanical properties, making them challenging to process into devices. Conventional strengthening strategies usually lead to a trade-off with refrigeration capacity reduction. Here, a novel design is presented to overcome this dilemma by forming dual-phase alloys through in situ precipitation of a tough magnetic refrigeration phase within an intermetallic compound with excellent MCE. In the alloy 87.5Gd-12.5Co, incorporating the interconnected tough phase Gd contributes to enhanced strength (≈505MPa) with good ductility (≈9.2%). The strengthening phase Gd simultaneously exhibits excellent MCE, enabling the alloy to achieve a peak refrigeration capacity of 720 J kg-1. Moreover, the alloy shows low thermal expansion induced by the synergistic effect of the two phases. It is beneficial for maintaining structural stability during heat exchange in magnetic refrigeration. The coupling interaction between the two magnetic phases can broaden the refrigeration temperature range and reduce hysteresis. This study guides the development of new high-performance materials with an excellent combination of mechanical and magnetic refrigeration properties as needed for gas liquefaction and refrigerators.

Magnetic refrigeration property and single-molecule magnetic behavior of three asymmetric Ln2 (LnIII = Gd, TB and Dy) compounds

Three new dinuclear Ln(III)-based compounds formulated as {Ln2(dbm)5L}·nMeOH (Ln = Gd (1), Tb (2), and Dy (3), Hdbm = dibenzoylmethane, HL = 2-hydroxyimino-propionic acid (6-methoxy-pyridin-2-ylmethylene)-hydrazide, MeOH = methanol) have been successfully synthesized under solvothermal conditions. The structures and magnetic properties of 1–3 have been systematically studied. The single-crystal X-ray diffraction analysis shows that compounds 1–3 are dinuclear structures with two asymmetric LnIII ion centres. The magnetic properties study suggests that compound 1 displays cryogenic magnetic refrigeration property, while compound 3 exhibits single-molecule magnetic behavior with an energy barrier (ΔE/kB) of 62.3 K and pre-exponential factor τ0 = 2.93 × 10-8 s under a zero direct-current field.

LnIII2 compounds constructing by polydentate Schiff base ligand and β-diketonate coligand: structures, magnetocaloric effect and SMMs behaviors

Four new LnIII2 compounds [Ln2(dbm)2(L)2(CH3OH)] (Ln(III) = Gd (1), Tb (2), Ho (3), and Tm (4)), where H2L is 2-hydroxyamino-propionic acid (3,5-di-tert-butyl-2-hydroxy-benzylidene)-hydrazide and Hdbm is dibenzoylmethane, were successfully synthesized via solvothermalmethod and characterized structurally and magnetically. Magnetic studies reveal the anti-ferromagnetic interaction was existed in compound 1. Moreover, magnetic refrigeration property study suggests that compound 1 exhibits magnetocaloric effect with − ΔSm = 21.07 J kg−1 K−1 for ΔH = 7.0 T at 2.0 K. Alternating-current (ac) magnetic susceptibility study of 2 and 3 suggests that single-molecule magnet (SMM) behavior occurs for 2 and 3 under Hdc = 0 Oe with the effective energy barrier ΔE/kB of 20.05 K and τ0 of 2.93 × 10−6 s for 2 and ΔE/kB = 0.85 K and τ0 = 3.47 × 10−5 s for 3.

Three Ln2 compounds (Gd2, Tb2 and Dy2) with a Ln2O2 center showing magnetic refrigeration property and single-molecular magnet behavior

Three dinuclear Ln2 compounds, [Ln2(dbm)4(L-)2]·4CH3CN (Ln = Gd (1), Tb (2), Dy (3), HL = (E)-N'-(2-hydroxybenzylidene)benzohydrazide and dbm = dibenzoylmethane), have been obtained by a solvent evaporation method. The structural analyses indicate that the three Ln2 compounds (Gd2, Tb2 and Dy2) are isostructural with a Ln2O2 center. Magnetic investigations show the presence of magnetic refrigeration in the Gd-based compound with a -ΔSm value of 17.62 J kg−1 K−1 (T = 2.0 K and ΔH = 7.0 T); for compound 3, however, single-molecular magnet behavior (SMM) was observed (Ueff /kB = 0.84 K and τ0 = 1.08 × 10−5 s).

Four Ln2 compounds constructed by a polydentate Schiff base ligand: Gd2 compound displaying large magnetocaloric effect and Dy2 compound showing single-molecule magnet behavior

Four new acyloxy bridged LnIII2 compounds [Ln2(L)2(acac)2(EtOH)2] (Ln(III) = Gd (1), Tb (2), Dy (3), and Ho (4), Hacac = acetylacetone, and H2L = pyridine-2-carboxylic acid (3-ethoxy-2-hydroxy-benzylidene)-hydrazide) have been prepared by a polydentate Schiff base ligand under solvothermal condition. The single-crystal X-ray structure study reveals that 1–4 are isostructural and contain a parallelogram Ln2O2 core. Magnetic study reveals that antiferromagnetic interaction exists in compound 1. More importantly, compound 1 displays well cryogenic magnetic refrigeration property (−ΔSm = 28.2 J kg−1 K−1, T = 2.0 K and ΔH = 70 kOe); while compound 3 exhibits evident single-molecule magnet behavior under zero-field condition (ΔE/kB = 26.8 K, τ0 = 1.05 × 10−7 s).

Larger magnetocaloric effect and single molecule magnet behavior in dinuclear Ln(III)-based compounds constructed from Schiff base ligand

A series of Ln(III)-based compounds with the formula [Ln2(HL)2(acac)2(CH3OH)2] (Ln (III) = Gd (1), Tb (2), Dy (3), Ho (4) and Er (5), Hacac = acetylacetone, H3L = 3-hydroxy-N’-[(1E)-(2-hydroxy-3-methoxyphenyl)methylidene]pyridine-2-carbohydrazide) based on a flexible Schiff base ligand H3L have been successfully synthesized, and the structures and magnetic properties of 1–5 have been systematacially studied. The crystal structures study indicates that compounds 1–5 are isostructural and possess a parallelogram Ln2O2 core. Magnetic properties measurements reveal that an antiferromagnetic interaction is exsisted in 1 and ferromagnetic interactions are exsisted in compounds 3 and 4. Remarkably, compound 1 displays well cryogenic magnetic refrigeration property with a larger magnetic entropy (−ΔSm = 28.79 J K−1 kg−1, T = 2.0 K and ΔH = 70 kOe). Moreover, alternating-current (ac) magnetic susceptibility research reveals that compound 3 shows slow magnetic relaxation behavior under zero dc field. Furthermore, under an external dc field of 1500 Oe, compound 3 displays remarkable SMM behavior with the effective barrier (ΔE/kB) of 14.9 K.

Structures and magnetic properties of two dinuclear lanthanide complexes based on 8-hydroxyquinoline Schiff base derivatives

Based on 8-hydroxyquinoline Schiff base derivative and auxiliary ligand β-diketonate, two new dinuclear lanthanide complexes [Gd2(L1)2(bfac)4] (1) and [Dy2(L2)2(acac)2(CH3OH)2]•CH3OH (2) (HL1 = 2-[((4-phenethyl)-imino)methyl]-8-hydroxyquinoline, H2L2 = 2-[((4-methyl)-2-(arboxyl)-imino)]methyl]-8-hydroxyquinoline, Hbfac = hexafluoroacetylacetonate, Hacac = acetylacetonate,) were successfully isolated and characterized. Structural analysis reveal that complexes 1 and 2 both contain a binuclear Ln2 cluster, in which two eight-coordinated Ln(III) ions are located in distorted dodecahedral geometry and bridged by phenoxide oxygen atom. In addition, their magnetic properties are investigated in detail. The results suggest that ferromagnetic interactions between adjacent Gd3+ ions can be observed in 1, which exhibits remarkable magnetic refrigeration properties with -ΔSmax = 17.74 J kg−1 K−1 (T = 2.0 K and ΔH = 7.0 T). Complex 2 displays slow magnetic relaxation behaviors with ΔE/kB ≈ 2.16 K and τ0 ≈ 1.38 × 10−5 s.

Structures and magnetic properties of acyloxy-O bridged Ln2 compounds: Gd2 compound displaying magnetic refrigeration property

In order to study magnetocaloric effect, we synthesized five new dinuclear lanthanide (Ⅲ) compounds, namely [Ln(dbm)2HL(CH3OH)]2•2CH3OH (LnⅢ=Nd(1), Gd(2) and Tm(5), dbm =1,3-diphenylpropane-1,3‑dione, HL = N'-[(1E)-[5-(hydroxymethyl)furan-2-yl]methylidene]pyrazine-2-carbohydrazide) and [Ln(dbm)2HL]2 (LnⅢ = Ho(3) and Er(4)), and characterized by elemental analysis, IR, PXRD, UV–vis and single crystal X-ray diffraction. The structures of compounds 1–5 are very similar with a planar [Ln2O2]. Magnetic studies indicated that weak antiferromagnetic interaction are present between the Gd(Ⅲ) ions within 2. Meanwhile, Gd2 compound displays magnetic refrigeration property with the max entropy change (-ΔSm) of 16.58 J K − 1kg−1 (T = 2.0 K and ΔH = 70 kOe).

Structure, Magnetic Refrigeration Property and Single-Molecule Magnetic Behavior of Three Asymmetric Ln2 (LnIII = Gd, Tb and Dy) Compounds

Structure, Magnetic Refrigeration Property and Single-Molecule Magnetic Behavior of Three Asymmetric Ln2 (LnIII = Gd, Tb and Dy) Compounds

Single molecule magnet behavior and magnetic refrigeration of carbonyl oxygen-bridged tetranuclear lanthanide complexes

Three lanthanide complexes were fabricated and characterized. 1 exhibited cryogenic magnetic refrigeration property and 3 displayed slow relaxation of the magnetization.

Magnetic refrigeration property and slow magnetic relaxation behavior of five dinuclear Ln(III)-based compounds

In this work, a series of dinuclear Ln(III)-based compounds with the molecular form [Ln2(L)2(dbm)2(H2O)2]·nCH3OH (Ln(III) = Eu (1), Gd (2), Tb (3), Dy (4) and Ho (5), Hdbm = 1,3-diphenyl-1,3-propanedione and H2L = 2-[(1E)-{[(pyridin-2-yl)formamido]imino}methyl]benzoic acid) have been successfully synthesized using a polydentate Schiff base ligand (H2L) and reacting it with the β-diketone salts Ln(dbm)3·2H2O. The crystal structures and magnetic properties of the five Ln2 compounds have been completely studied. The crystal structure studies reveal that compounds 1–5 are isostructural and show a dinuclear structure with a parallelogram Ln2O2 core. The magnetic research suggests that the Gd2 compound shows a cryogenic magnetic refrigeration property with magnetic entropy (−ΔSm) = 23.2 J K−1 kg−1 (T = 2.0 K and ΔH = 7.0 T), while the Dy2 compound exhibits slow magnetic relaxation behavior.

A novel tetranuclear Gd(III)-based cluster showing larger magnetic refrigeration property

A novel tetranuclear Gd(III)-based cluster, namely [Gd4(HL)4(CH3O)4] •3CH3OH (1), has been successfully synthesized by using a polydentate Schiff base ligand (H3L) reacted with Gd(acac)3•2H2O. The crystal structure and magnetic property of cluster 1 have been completely studied. Crystal structure study reveals that cluster 1 is a tetranuclear compound and the four center Gd(III) ions display a tetrahedral arrangement. The magnetic research suggests that cluster 1 shows cryogenic magnetic refrigeration property with a larger magnetic entropy (−ΔSm = 30.42 J K−1 kg−1, T = 2.0 K and ΔH = 7.0 T).

Two Ln(III)2 (Ln = Gd and Dy) compounds showing magnetic refrigeration and slow magnetic relaxation

Two new Ln2 compounds, namely [Ln2(L)2(CH3OH)2] (Ln = Gd (1) and Dy (2)), have been successfully synthesized and further characterized by crystallography. Structural analysis shows that both 1 and 2 are binuclear compounds, and each LnIII ion is eight-coordinated model and the coordination polyhedron of centre LnIII ion can be represented as a distorted dodecahedron with triangular faces. The magnetic studies reveal that weak antiferromagnetic exchange is existed between the two neighbouring Gd(III) ions in 1. Furthermore, for 1, it exhibits magnetic refrigeration property (magnetic entropy changes −ΔSm = 24.75 J kg−1 K−1 for magnetic field intensity ΔH = 7.0 T at 3.0 K); while for 2, it displays slow magnetic relaxation behavior under zero dc field. When under an external dc field (dc = 3000 Oe), remarkable single-molecule-magnet (SMM) behavior was observed in 2 with the anisotropic barrier (ΔE/kB) of 16.65 K and pre-exponential factor (τ0) of 3.12 × 10−6 s.

Construction of a family of Ln3 clusters using multidentate Schiff base and β-diketonate ligands: fluorescence properties, magnetocaloric effect and slow magnetic relaxation

Seven μ-Oacylhydrazone-bridged Ln3 clusters were synthesized. Cluster 3 displayed magnetic refrigeration properties, whereas cluster 5 showed slow magnetic relaxation. The solid-state fluorescence properties of 2, 4 and 5 were also studied.

Two LnIII4 (LnIII = Gd and Dy) clusters constructed by 8-hydroxyquinoline schiff base and β-diketonate coligand: Magnetic refrigeration property and single-molecule magnet behavior

Reaction between Ln(acac)3·2H2O (LnIII = Gd and Dy) and an 8-hydroxyquinoline Schiff base (HL) via solvothermal conditions yielded two new LnIII4 clusters [Ln4(acac)4(μ3-OH)2L6]·2CH3CN (HL = 5-(9-anthranylene)-8-hydroxylquinoline, Hacac = acetylacetone). In this paper, the structures and magnetic properties of the two LnIII4 clusters have been systematically characterized and studied. Structural studies indicate that both clusters 1 and 2 crystallize in the monoclinic space group P21/c. The four LnIII4 ions form a rhombus-shaped arrangement. Physical characterization reveals that cluster 1 displays the property of magnetic refrigeration with −ΔSm of 14.57 J kg−1 K−1 (ΔH = 7 T and T = 3.0 K), while cluster 2 shows single-molecule magnet (SMM) behavior with a large effective energy barrier (ΔE/kB) of 73.6 K.

Synthesis, structures and magnetic refrigeration properties of four dinuclear gadolinium compounds

Four new Gd2 compounds, [Gd2(L1)2(acac)2(CH3O)2] (1), [Gd2(L1)2(beac)2(OH)2] (2), [Gd2(L2)2(C4H10O3)2(CH3OH)2] (3) and [Gd2(L3)2(acac)2(CH3O)2] (4), were synthesized by solvent evaporation methods and studied by structural analyses and magnetic analyses. Crystallographic studies reveal that these compounds are dinuclear compounds and each center Gd(III) ion is eight-coordinated. The magnetic studies reveal that 1–4 display cryogenic magnetic refrigeration properties with −ΔSMax values of 24.80 J kg−1 K−1 for 1 (T = 3.0 K and ΔH = 7.0 T), 25.45 J kg−1 K−1 for 2 (T = 2.0 K and ΔH = 7.0 T), 21.12 J kg−1 K−1 for 3 (T = 3.0 K and ΔH = 7.0 T), and 31.33 J kg−1 K−1 for 4 (T = 2.0 K and ΔH = 7.0 T).

Structures and magnetic refrigeration properties of three Gd2 compounds

Three new Gd2 compounds, namely [Gd2(dbm)3(L1)2CH3O]·2.5CH3OH (1), [Gd2(tmhd)2(L2)2(CH3O)2] (2) and [Gd2(acac)2(L3)2(CH3O)2] (3) (Hdbm = 1,3-dip henyl-1,3-propanedione, Htmhd = 2,2,6,6-tetramethyl-3,5-heptanedione and Hacac = acetylacetone), have been synthesized via a mixed ligands approach and structurally characterized. Magnetic studies reveal that 1–3 display cryogenic magnetic refrigeration properties (−ΔSm = 19.13 J kg−1 K−1 for ΔH = 7 T at 2.0 K for 1, −ΔSm = 21.06 J kg−1 K−1 for ΔH = 7 T at 2.0 K for 2 and −ΔSm = 25.73 J kg−1 K−1 for ΔH = 7 T at 2.0 K for 3).

Single molecule magnet behavior and magnetic refrigeration of four tetranuclear lanthanide (Ln = GdIII, TbIII, DyIII) clusters

Four lanthanide complexes were fabricated and characterized. 1 and 4 exhibit a cryogenic magnetic refrigeration property and 3 displays slow relaxation of magnetization.

Tetranuclear lanthanide complexes showing magnetic refrigeration and single molecule magnet behavior

Four tetranuclear lanthanide complexes were fabricated and characterized. 1 exhibits cryogenic magnetic refrigeration property and 3 displays slow relaxation of the magnetization.

Structures, luminescent and magnetic properties of three dinuclear lanthanide complexes: Magnetic refrigeration and single-molecule magnet behaviour

Three dinuclear lanthanide complexes: {[Ln2(L)2(pbd)4]·2CH3CN} (Ln = Eu (1), Gd (2), Dy (3); HL = 2-(hydroxyimino)-N′-(pyridin-2-ylmethylene)propanehydrazonic acid, pbd = 1-phenylbutane-1,3-dione) were fabricated and structurally characterized. Compounds 1–3 are isostructural belonging to the monoclinic system with space group C2/c. Magnetic studies reveal that 2 exhibits cryogenic magnetic refrigeration property (−ΔSm = 21.20 J K−1 kg−1), whereas compound 3 displays slow relaxation of the magnetization. Additionally, solid-state luminescence measurements reveal that 1 displays the characteristic Eu (III) luminescence at room temperature.