Significant Magnetocaloric Effect Research Articles

A comparative study of the magnetic and transport properties of Dy-In based intermetallic compounds

A comparative study of the magnetic and transport properties of three Dy-In intermetallic compounds, namely DyIn3, Dy5In3 and Dy3In, is reported. DyIn3 has cubic crystal structure; on the other hand, Dy5In3 and Dy3In crystallize in tetragonal structure, albeit with different space groups. DyIn3 orders antiferromagnetically below TN = 23 K, while Dy5In3 and Dy3In show ferromagnetic-like ground state with much higher ordering temperatures (119 and 125 K respectively). The ferromagnetic compounds show significant magneto-caloric effect around their respective Curie temperatures. On the other hand, the magneto-caloric effect in DyIn3 is low but associated with the change in sign around TN. All the samples show small magneto-resistance, and it is found to be positive in case of DyIn3 at 5 K. The signature of metamagnetic transition in DyIn3 is visible in the magneto-caloric and magneto-resistance data. Efforts have been made to account the observed magnetic phenomena based on Dy concentration and Dy-Dy bond distance in these three compositions.

Two series of lanthanide complexes with 4-chlorophenylacetate ligand displaying luminescence and significant magnetocaloric effect

Two series of lanthanide complexes based on 4-chlorophenylacetic acid (HCPA), dinuclear [Ln2(CPA)6(DMF)2(H2O)2] (Ln = Eu (1); Gd (2); Tb (3); Dy (4)) and one-dimensional (1D) linear [Ln2(CPA)6(H2O)]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 H2O/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 −ΔSm 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.

Cosubstitution in Ni-Mn-Sb Heusler compounds: Realization of room-temperature reversible magnetocaloric effect driven by second-order magnetic transition

Materials showing reversible magnetocaloric effect near room temperature are desirable for green refrigeration technology. The compounds in the magnetic Heusler family displaying significant magnetocaloric effect driven by first-order magnetostructural transitions are in vogue. Comparatively, Heusler compounds undergoing second-order magnetic transition near room temperature are less explored in the context of discovering significant magnetocaloric effects, though they can offer certain advantages like less energy cost and hysteresis loss. Using density-functional theory in conjunction with model Hamiltonians, we explore potential room-temperature magnetocaloric materials near second-order magnetic transition by cosubstitution in the Ni-Mn-Sb family. Our investigation on two cosubstituted families, ${\mathrm{Ni}}_{2\ensuremath{-}x}{\mathrm{Fe}}_{x}{\mathrm{Mn}}_{1+z\ensuremath{-}y}{\mathrm{Cu}}_{y}{\mathrm{Sb}}_{1\ensuremath{-}z}$ and ${\mathrm{Ni}}_{2\ensuremath{-}x}{\mathrm{Co}}_{x}{\mathrm{Mn}}_{1+z\ensuremath{-}y}{\mathrm{Cu}}_{y}{\mathrm{Sb}}_{1\ensuremath{-}z}$, discovers significant numbers of compounds with second-order phase transition near room temperature exhibiting significant changes in magnetic entropy, comparable to that observed in the compounds showing inverse magnetocaloric effect near a first-order magnetostructural transition. We provide a systematic way to select potential reversible magnetocaloric compounds and analyze our results from their electronic structures and magnetic exchange interactions.

Understanding the origin of the magnetocaloric effects in substitutional Ni-Mn-Sb-Z(Z=Fe,Co,Cu) compounds: Insights from first-principles calculations

Ni-Mn based ternary Heusler compounds have drawn attentions lately as significant magneto-caloric effects in some of them have been observed. Substitution of Ni and Mn by other $3d$ transition metals in controlled quantity have turned out to be successful in enhancing the effect and bring the operational temperatures closer to the room temperature. Using density functional theory calculations, in this work, we have systematically explored the roles of various factors such as site occupancies, magnetic interactions, and compositions associated with the constituents of Mn-excess Ni$_{2}$MnSb Heusler compounds upon substitution of Ni and/or Mn by $3d$ transition metals Fe, Co and Cu. Our calculations unveiled the physics behind the variations of physical properties associated with the magneto-caloric effects, and thus interpreted the available experimental results successfully. The work also provided important information on the compounds and the composition ranges where significant magneto-caloric effects may be realised and further experimental investigations need to be done.

Significant magnetocaloric effect in a ferromagnetic {CrIII2GdIII3} cluster

A pentanuclear {Cr2Gd3} cluster (1) and its diamagnetic substituent-{Al2Gd3} (2) based on pivalic acid (Hpiv) were obtained with the formulas of {Et3NH[M2Gd3(OH)6(piv)10(H2O)2]} (M = CrIII, 1; AlIII, 2). The metallic core shows a triangle bipyramid-{Cr2Gd3} held together by six µ3-OH groups, and the piv- ligands located at the periphery. Magnetic studies for complex 1 exhibit dominant ferromagnetic interactions between CrIII and GdIII ions. Furthermore, ferromagnetic {Cr2Gd3} cluster (1) displays a considerable large magnetic entropy value (−ΔSm = 27.0 J kg−1 K−1) at high temperature among low-nuclearity 3d-4f clusters.

Influence of A-Site cation size-disorder on the magnetocaloric response of La0.6CaxSr0.4-xMnO3 nanoparticles

Building on previous work finding a significant magnetocaloric effect (MCE) in manganite nanoparticles having the formula La0.60Cax Sr0.40-xMnO3 (0<x<0.4), which show promise for application in magnetic refrigeration systems. These were synthesized via a Pechini sol-gel method, as verified by powder x-ray diffraction and laser ablation-inductively coupled plasma-mass spectrometry. The temperature-dependence of the magnetic entropy change between 200K and 320K in a magnetic field of μH=3T was evaluated by means of Maxwell’s relations and isothermal MH curves. The reported values of ΔSmax increase from 1.5 J kg-1K-1 to 5.6 J kg-1K-1 as x increases from 0 to 0.4. Ms; crystallite size and b and c lattice parameters increase with x. The results show a clear positive correlation between calcium concentrations and the value of -ΔS, suggesting that a larger atom at the calcium site negatively impacts the magnetocaloric effect, thereby decreasing magnetic refrigeration viability.

Magnetism, magnetocaloric and magnetodielectric properties of DyVWO6: a new aeschynite-type polar antiferromagnet

We report magnetic, magnetocaloric and magnetodielectric properties of a new polar magnet DyVWO6 crystallizing in the orthorhombic structure (Pna21). It consists of edge-shared dimers of VO6 and WO6 octahedra, which are connected by corner-sharing to a form three-dimensional network structure with Dy3+ cations located in the channels. The ordering of V3+ and W6+ ions in the octahedral sites breaks the inversion symmetry of the parent-CaTa2O6 structure (Pnma). Magnetic and heat capacity measurements show that the V3+ and Dy3+ ions undergo antiferromagnetic transitions at ∼ 5 K and ∼ 2.5 K, respectively. Isothermal magnetization shows a metamagnetic transition at the applied magnetic field of 1 T at 2 K that corresponds to a transition from the antiferromagnetic (AFM) to ferromagnetic (FM) spin structure. Further, this compound exhibits significant magnetocaloric effect (MCE) with a maximum magnetic entropy change (−∆) of 8.45 J Kg−1 K−1 at 7 T. In addition to this, we observe a drop in dielectric constant below with a low temperature dielectric relaxation.

Room temperature magnetocaloric effect in polycrystalline La0.75Bi0.05Sr0.2MnO3

In this work, we have investigated the magnetic and magnetocaloric properties of polycrystalline La0.75Bi0.05Sr0.2MnO3 prepared by sol–gel method. Structural analysis has shown that this compound crystallizes in the rhombohedral structure with R\( \bar{3} \)c space group. The magnetic study revealed that our sample exhibits a ferromagnetic–paramagnetic transition at 300 K. A significant magnetocaloric effect in the vicinity of the room temperature was detected for this sample (for only 2T applied field, the maximum of magnetic entropy change |∆SMax| = 1.75 J/kg K and the relative cooling power RCP = 77.12 J/kg). The obtained results suggest the possibility of using this compound as a magnetic refrigerant.

Ground-state ferrimagnetism and magneto-caloric effects in Nd2NiMnO6

Extending our earlier investigation of magnetic properties of Nd2NiMnO6, we show that it exhibits a magnetic transition below ∼6 K to a ferrimagnetic state. This behavior is interpreted as arising from a long-range ordering of Nd moments antiferromagnetically coupled to the ferromagnetic Ni–Mn ordered moments. Due to the richness of its multiple magnetic transitions and the easily influenced magnetic state by the application of an external magnetic field, established in our earlier study, it has a remarkable inverse magneto-caloric effect (IMCE) at low temperatures (T < 50 K) together with a significant conventional magneto-caloric effect (CMCE) at the ferromagnetic ordering temperature (Tc ∼ 200 K). IMCE and CMCE correspond to the antiferromagnetic arrangement of Nd and Ni–Mn sublattices and ferromagnetic ordering of Ni–Mn sublattices, respectively. Nd2NiMnO6 with its second order phase transition follows the universal behavior of ∆SM(T); it also shows a power law dependency on the magnetic field as

Lanthanide-Based Layer-Type Two-Dimensional Coordination Polymers Featuring Slow Magnetic Relaxation, Magnetocaloric Effect and Proton Conductivity.

Three lanthanide-based two-dimensional (2D) coordination polymers (CPs), [Ln(L)(H2 O)2 ]n , {H3 L=(HO)2 P(O)CH2 CO2 H; Ln=Dy3+ (CP 1), Er3+ (CP 2)} and [{Gd2 (L)2 (H2 O)3 }. H2 O]n , (CP 3) were hydrothermally synthesized using phosphonoacetic acid as a linker. Structural features revealed that the dinuclear Ln3+ nodes were present in the 2D sheet of CP 1 and CP 2 while in the case of CP 3, nodes were further connected to each other forming a chain-type arrangement throughout the network. The magnetic studies show field-induced slow magnetic relaxation property in CP 1 and CP 2 with Ueff values of 72 K (relaxation time, τ0 =3.05×10-7 s) and 38.42 K (relaxation time, τ0 =4.60×10-8 s) respectively. Ab-initio calculations suggest that the g tensor of Kramers doublet of the lanthanide ion (Dy3+ and Er3+ ) is strongly axial in nature which reflects in the slow magnetic relaxation behavior of both CPs. CP 3 exhibits a significant magnetocaloric effect with -ΔSm =49.29 J kg-1 K-1 , one of the highest value among the reported 2D CPs. Moreover, impedance analysis of all the CPs show high proton conductivity with values of 1.13×10-6 S cm-1 , 2.73×10-3 S cm-1 and 2, 6.27×10-6 S cm-1 for CPs 1-3, respectively, at high temperature (>75 °C) and maximum 95 % relative humidity (RH).

Cl--Templated Assembly of Novel Peanut-like Ln40Ni44 Heterometallic Clusters Exhibiting a Large Magnetocaloric Effect.

Two novel and fascinating high-nuclearity lanthanide-transition (4f-3d) heterometallic clusters were obtained based on an anion-template (Cl-) and ligand-controlled approach, formulated as [Gd40Ni44(CO3)12(CH3COO)4(IDA)44(C2O4)(μ2-O)4(μ3-OH)60(μ3-O)6(H2O)12]·Cl10·20H2O (abbreviated as Gd40Ni44, 1) and [Eu40Ni44(CO3)12(CH3COO)6(IDA)44(C2O4)(μ2-O)4(μ3-OH)62(μ3-O)4(H2O)12]·Cl10·23H2O (abbreviated as Eu40Ni44, 2), where H2IDA = iminodiacetic acid and H2C2O4 = oxalic acid. Structural analysis exhibits that the compounds 1 and 2 were both constructed by two enticing bowl-like anion units Ln20Ni22, featuring peanut-like structures. Besides, the assembly of Ln20Ni22 was templated by five Cl- ions. Magnetically, compound 1 shows a significant magnetocaloric effect, with -ΔSm = 36.05 J kg-1 K-1 at 3 K for ΔH = 7 T.

An experimental and theoretical study of magnetocaloric effect in Nd0.5Dy0.5FeO3

A significant magnetocaloric effect (MCE) has been revealed in our investigation on polycrystalline Nd0.5Dy0.5FeO3 below 30 K. Observed magnetization of the system at low temperature is 32% higher than the expected average magnetization of NdFeO3 and DyFeO3. Such an enhancement in the magnetization led to a large change in magnetic entropy (10.4 Jkg−1 K−1) at 4 K. The observed entropy change is remarkable considering the higher natural abundance of Nd compared to that of Dy and negligible MCE seen in case of NdFeO3. Theoretical calculations performed using mean-field approximation and Monte Carlo simulations on an Ising type spin model indicate that the high magnetocaloric effect is caused primarily by the ordering of rare-earth ions in C-type antiferromagnetic state in presence of molecular exchange field created by Fe ions.

Two linear-shaped Gd4 clusters based on a multidentate ligand: Synthesis, structures, and magnetic refrigeration

Two novel and tetranuclear gadolinium clusters, namely, [Gd4(L)2(dbm)6(CH3OH)2] (1) and [Gd4(L)2(dbm)6(C2H5OH)2] (2) (H3L = (6-Hydroxymethyl)-N′-((2,3-dihydroxyphenyl)-methylene)picolinohydrazide and dbm = dibenzoylmethane), were assembled by the reaction of a multidentate ligand H3L with Gd(dbm)3·2H2O in different solvent system. Both the two Gd4 clusters have an approximate linear-shaped arrangement and the four central Gd3+ ions are connected by six μ2-O atoms. Direct-current (dc) magnetic susceptibility measurements of clusters 1 and 2 indicated that the weak antiferromagnetic interactions between adjacent Gd3+ ions both exist in clusters 1 and 2. It's particularly significant that clusters 1 and 2 display significant cryogenic magnetocaloric effects with maximum −ΔSm values of 21.39 and 20.26 J kg−1 K−1 at 2.0 K and 7.0 T, respectively.

A series of new octanuclear Ln8 clusters: magnetic studies reveal a significant cryogenic magnetocaloric effect and slow magnetic relaxation

A series of new octanuclear Ln8 clusters. Magnetically, Gd8 exhibited a significant magnetocaloric effect and a magnetic entropy change is 32.49 J K−1 kg−1 for a field of 7 T at 2 K, while Dy8 exhibited a frequency dependent slow relaxation of magnetization at a zero applied direct current magnetic field.

Tuning the Topology from fcu to pcu: Synthesis and Magnetocaloric Effect of Metal–Organic Frameworks Based on a Hexanuclear Gd(III)-Hydroxy Cluster

Two polynuclear, cluster-based metal–organic frameworks (MOFs), formulated as {H2[Gd6(OH)8(H2O)6(p-BDC-F4)6]·3(2,2′-bpy)·6H2O} (1) and {H2[Gd6(OH)8(H2O)6(m-BDC-F4)6]·3(4,4′-bpy)·6H2O} (2) (p-BDC-F4 = tetrafluoroterephthalic acid, m-BDC-F4 = tetrafluoroisophthalic acid), are synthesized by hydrothermal reactions of GdIII ions with perfluorinated benzenedicarboxylate. Structure analysis illustrates that both 1 and 2 are constructed by the hexanuclear GdIII-hydroxy cluster molecular building block {Gd6(OH)8(COO)12(H2O)6}, generating a 12-connected fcu-MOF and a 6-connected pcu-MOF, respectively. Compounds 1 and 2 are stable in some refluxing organic solvents, boiling water, and aqueous solutions in the pH range of 2–11. Notably, magnetic investigation indicates that 1 and 2 display a significant magnetocaloric effect.

Diverse Lanthanide Coordination Polymers with 3,3'-Dimethylcyclopropane-1,2-dicarboxylate Ligand: Synthesis, Crystal Structure, and Properties.

In an attempt to investigate the influence of many variables on the synthesis of lanthanide coordination polymers (Ln-CPs) assembled from the ligand 3,3-dimethylcyclopropane-1,2-dicarboxylic acid, three different Ln-CPs with formulae [La9(μ4-dcd)12(μ3-O)2(H)]n (1), [Gd4(μ4-dcd)6(H2O)]n (2), and [Gd2(μ3-OH)2(μ3-dcd)(μ2-ac)2(H2O)]n (3) (dcd = 3,3-dimethylcyclopropane-1,2-dicarboxylate, ac = acetate) have been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectrum, thermal analysis, powder X-ray diffraction, and single X-ray diffraction techniques. 1 represents the first report of the three-dimensional (3D) Ln-CPs based on nonanuclear lanthanide clusters, although it shows extremely low gas uptakes. 2 exhibits one of the previously reported 3D lanthanide wheel cluster-like frameworks. 3 characterizes a novel one-dimensional ladder-like chain [Gd4(OH)4]n decorated with mixed ligand ribbons. Variable-temperature magnetic susceptibility measurement reveals that the shortest Gd···Gd distance in 3 induces the antiferromagnetic interactions between adjacent Gd3+ cations within the hydroxyl-bridged binuclear unit. Remarkably, magnetic investigation for 2 indicates a unique metamagnetic transition from the antiferromagnet to ferromagnet. Furthermore, magnetic studies for 2 also exhibit the presence of significant magnetocaloric effect with a large magnetic entropy change.

Two Pairs of Chiral "Tower-Like" Ln4 Cr4 (Ln=Gd, Dy) Clusters: Syntheses, Structure, and Magnetocaloric Effect.

Two pairs of novel chiral chromium lanthanide compounds, formulated as l- and d-[Gd4 Cr4 (IN)10 (μ3 -OH)4 (μ4 -O)4 (H2 O)12 ]⋅[IN]2 ⋅8 H2 O (1 and 3), and l- and d-[Dy4 Cr4 (IN)11 (μ3 -OH)4 (μ4 -O)4 (H2 O)8 ]⋅[IN]⋅1.5 H2 O (2 and 4) (HIN=isonicotinic acid) have been successfully synthesized and characterized. Structural analysis reveals that four Ln3+ ions and four Cr3+ ions connect with each other and yield a "tower-like" [Ln4 Cr4 ] skeleton. Apart from the above featuring an aesthetically charming structure, circular dichroism (CD) spectra confirm that compounds 1 and 3, 2 and 4 are enantiomers. To the best of our knowledge, these are the largest chiral chromium lanthanide compounds. In addition, magnetic interaction shows that Gd (the mixture of 1 and 3) exhibits significant cryogenic magnetocaloric effect (MCE) with -ΔSm =18.08 J kg-1 K-1 (34.69 mJ cm-3 K-1 ). Also, the observed second-harmonic generation efficiencies of [Gd4 Cr4 (IN)10 (μ3 -OH)4 (μ4 -O)4 (H2 O)12 ]⋅[IN]2 ⋅8 H2 O and [Dy4 Cr4 (IN)11 (μ3 -OH)4 (μ4 -O)4 (H2 O)8 ]⋅[IN]⋅1.5 H2 O are 0.3 and 0.4 times that of urea, respectively.

Cryogenic magnetic properties and magnetocaloric performance in double perovskite Pr2NiMnO6 and Pr2CoMnO6 compounds

Double perovskite Pr2NiMnO6 (PNMO) and Pr2CoMnO6 (PCMO) ceramics have been synthesized and their crystal structure, microstructure, as well as cryogenic magnetic properties and magnetocaloric performance have been investigated. The crystal structure of PNMO and PCMO ceramics was determined to be monoclinic with space group of P21/n at room temperature. A ferromagnetic to paramagnetic (FM-PM) phase transition (second-order) occurred in PNMO and PCMO around 208 and 170 K, respectively. Significant reversible magnetocaloric effect (MCE) was found and the values of the maximum magnetic entropy change (-ΔSMmax) were 3.15 and 3.91 J/kg-K under the magnetic field change (ΔH) of 0–7 T in PNMO and PCMO, respectively. The corresponding relative cooling power (RCP) values were 241.9 and 229.9 J/kg.

Nanosized Chiral [Mn6Ln2] Clusters Modeled by Enantiomeric Schiff Base Derivatives: Synthesis, Crystal Structures, and Magnetic Properties

Two enantiomeric pairs of new 3d-4f heterometallic clusters have been built from two enantiomer Schiff base derivatives, labeled as R-/ S-H2L, in situ obtained from the condensation reactions with o-vanillin and R-/ S-2-phenylglycinol. The formulas of the series clusters are [Mn6Ln2(μ3-OH)4(μ4-O)(Ac)4(H2O)2( R-L)6]·NO3·OH (Ln = Dy (1R), Gd (2R)), [Mn6Ln2(μ3-OH)4(μ4-O)(Ac)4(H2O)2( S-L)6]·NO3·OH (Ln = Dy (1S), Gd (2S)), whose crystal structures and magnetic properties have been characterized. Structural analysis indicated that the above clusters consisted of a [Mn6Ln2] core, featuring a sandwich configuration. The results of magnetic measurements showed the presence of slow magnetic relaxation with the effective energy barrier of 14.85 K in two Dy derivatives under the condition of zero-dc field, while the significant magnetocaloric effect of Gd analogues was found in a wide temperature range.

Large room temperature adiabatic temperature variation in a Ni40Co8Mn42Sn10 polycrystalline alloy

For the potential applications in magnetic refrigeration, low-cost and high-performance refrigerants with large magnetocaloric effect at relatively lower field change are highly desired. In this work, we report a large adiabatic temperature variation for a low-field change of 1.5 T near room temperature in a Ni40Co8Mn42Sn10 bulk alloy. With the large magnetization difference between weak magnetic martensite and ferromagnetic austenite, this alloy exhibits significant inverse magnetocaloric effect. Under the field change of 5 T, large magnetic entropy change ΔSM of 21.6 J kg−1K−1 and effective refrigeration capacity RCeff of 293 J kg−1 were achieved. Moreover, a large ΔTad up to −4.4 K was obtained under the low-field change of 1.5 T, which is much higher than previously reported ΔTad values in Ni-Mn-Sn based alloys.