ΔSM Values Research Articles

Magnetic and magnetocaloric properties in Ba-doped La0.7Ca0.3MnO3 nanoparticles

La0.7Ca0.3−xBaxMnO3 nanoparticles with the crystalline size d = 38 and 39 nm for x = 0.025, and 0.05, respectively, were synthesized by utilizing the solid-state reaction and mechanical ball milling methods. We have used the Banerjee's criteria, the mean-field, and the thermodynamic theories, and isothermal magnetization, M(H), data around Curie temperature (TC) to investigate the magnetic phase transformation and the temperature (T) and magnetic field (H) dependences of magnetic entropy change, ΔSm(T, H), for nanoparticles. These exhibit the samples undergoing a second-order magnetic phase transition with an existence of the short-range ferromagnetic order in the samples. Under an applied magnetic field change ΔH = 30 kOe, the maximum value of ΔSm (denoted as |ΔSmax|) are obtained about 4.4 J kg−1 K−1 corresponding to a relative cooling power (RCP) value about 140 J kg−1. Field dependences of |ΔSmax| and RCP can be expressed by the power laws, |ΔSmax| = a × Hn and RCP = b × HN, where a and b are coefficients, n and N are the field exponents, respectively. Interestingly, all the ΔSm(T, H) curves measured at different applied fields are collapsed onto a universal curve, ΔSm(T, H)/ΔSmax versus θ = (T − TC)/(Tr − TC), where Tr is the reference temperature.

Metamagnetic transition and magnetothermal properties of ErCo4Ge2

Polycrystalline ErCo4Ge2 was investigated by magnetic susceptibility and heat capacity measurements. The results show that ErCo4Ge2 undergoes a transition from the paramagnetic to the antiferromagnetic (AFM) state around 2.6 K. The second order character of this magnetic transition is confirmed from the lambda-like peak of the heat capacity data. Both χ′ and χ″ of ErCo4Ge2 are strongly dependent on the ac magnetic field frequency and bias dc magnetic field. A field induced metamagnetic transition from AFM to ferromagnetic state is observed below TN. Under a magnetic field change of 50 kOe, the maximum value of the magnetic entropy change (magnetocaloric effect) −ΔSM is 14.2 J/kg K at 2.75 K and the adiabatic temperature change ΔTad is 5.7 K. In particular, a large −ΔSM value of 11.7 J/kg K is achieved for a low magnetic field change of 20 kOe.

Large magnetic entropy change and relative cooling power in the rare earth intermetallic HoCo0.25Ni1.75 compound

Magnetic and magnetocaloric properties of cubic Laves phase rare earth intermetallic HoCo0.25Ni1.75 compound have been investigated. Magnetization measurements show that HoCo0.25Ni1.75 orders ferromagnetically at 22K (TC). The magnetization vs field (M–μ0H) isotherm at 2K shows negligible hysteresis. The isothermal magnetic entropy change (ΔSm) is calculated from the measured M–µ0H data near TC. The maximum value of ΔSm, ΔSmmax, is about −18.9J/kg-K at TC for a field change of 5T with a refrigerant capacity of 572J/kg. The material exhibits large ΔSmmax of −9.4J/kg-K even for a low field change of 2T. Universal master curve is constructed by rescaling ΔSm vs T curves for various fields to confirm the second order nature of the magnetic transition at TC. Large ΔSmmax value, wide temperature span of cooling and high relative cooling power make HoCo0.25Ni1.75 a potential magnetic refrigerant for low temperature applications such as hydrogen liquefaction.

Two Types of Cu-Ln Heterometallic Coordination Polymers with 2-Hydroxyisophthalate: Syntheses, Structures, and Magnetic Properties

Two types of Cu-Ln heterometallic coordination polymers (CPs), [Ln4Cu8(ipO)8(ox)2(H2O)12] (Ln = Sm (1); Eu (2); ipO = 2-hydroxyisophthalate; ox = oxalate) (type I) and [Ln2Cu6(ipO)6(H2O)12] [Ln = Gd (3); Tb (4); Dy (5)] (type II), were synthesized under the same hydrothermal conditions and structurally characterized. The first type of CPs displays a three-dimensional framework with a rare case of MoGe2 topology based on {Cu8} and {Ln2} secondary building units (SBUs), while the second type of CPs exhibits a chain structure built up from {Cu6} SBUs and Ln ions. Both of the {Cu8} and {Cu6} SBUs consist of planar [Cu2(ipO)2]2– units linked together by weak Cu–O bonds and π–π interactions. The structural variation from type I to type II can be ascribed to different reactions of H3ipO ligands induced by lanthanide ions. The magnetic investigations revealed that 3 displays a magnetocaloric effect (MCE) with a maximum −ΔSm value of 13.97 J kg–1 K–1 for ΔH = 50 kOe at 4.0 K. It was also found that 5 displays fiel...

Effect of particle size reduction on the magnetic phase transition and the magnetocaloric properties in ferromagnetic insulator La0.9Sr0.1MnO3 nanoparticles

The effect of the particle size reduction on ferromagnetic (FM) phase transition and magnetocaloric properties of the perovskite manganite La0.9Sr0.1MnO3 was studied. Indeed, it has been proven that the maximum of entropy change (−ΔSMmax) and the relative cooling power (RCP) are strongly affected by the particle size. The measured entropy change (ΔSM) was analyzed using Landau theory. The obtained results have been explained in terms of core–shell model. Moreover, H12 (La0.9Sr0.1MnO3 annealed at 1200°C) having large RCP and ΔSM values could be an interesting cooling material.

Mechanical properties and magnetocaloric effects in La(Fe, Si)13 hydrides bonded with different epoxy resins

The mechanical properties and magnetocaloric effect (MCE) of bonded La(Fe, Si)13 hydrides have been studied in detail. The mechanical strength increases with increasing the grade of epoxy resin from E-20 to E-51. This occurs because more pores and boundaries are filled with high grade resin since high epoxide content increases the degree of crosslinking and reduces the viscosity and shrinkage of resin. The compressive strength reaches 162 MPa for the bonded LaFe11.7Si1.3C0.2H1.8 with 3 wt. % E-51, which is 35% higher than that of bulk LaFe11.7Si1.3C0.2 compound (120 MPa). The mass ΔSM values remain almost same in bonded hydrides and are in a good agreement with the theoretical value. The maximum volumetric ΔSM values are 61.8, 58.0, and 54.7 mJ/cm3 K for bonded hydrides with epoxy resins E-20, E-44, and E-51, respectively, much higher than those of some magnetocaloric materials in same temperature range. The improved mechanical properties and large MCE indicate that bonded LaFe11.7Si1.3C0.2H1.8 is a promising material for room temperature magnetic refrigeration.

Tuning of normal and inverse magnetocaloric effect in Sm0.35Pr0.15Sr0.5MnO3 phase separated manganites

Magnetic and magnetocaloric properties of Sm0.35Pr0.15Sr0.5MnO3 polycrystalline manganite (bulk and nanometric samples) are investigated in detail. It has been observed that all the particle sizes (bulk to nano) show first order ferromagnetic→paramagnetic phase transition at low magnetic field. Ferromagnetic transition temperature also decreases with decreasing the particle size. This suggests that ferromagnetism is weakened and the first order magnetic phase transition is softened. We have investigated the magnetocaloric effect (MCE) of both bulk and nanometric samples around their spin glass-like transition temperature, Tg and Curie temperature, TC. It has been found that bulk sample exhibits both normal (i.e., negative ΔSM) and inverse (i.e., positive ΔSM) MCE around TC and after Tg, respectively. The value of ΔSM (+3.17Jkg−1K−1) at TC is almost three times larger than at Tg (ΔSM=−0.52Jkg−1K−1) for a magnetic field change of 7T. The bulk sample also exhibits a large relative cooling power (RCP) of 43.5J/kg for a magnetic field of 1T. The corresponding adiabatic temperature change of bulk sample is observed to be ∼1.5K for a magnetic field change of 3T. The value of ΔSM also decreases with reduction of particles sizes. The temperature width of ΔSM broadens with decreasing particle size. The value of ΔSM and the adiabatic temperature change vary with temperature and it is also found to be significant at all applied magnetic fields. Our results suggest that Pr3+ doping induces ferromagnetic clusters in the charge ordered matrix exhibiting large normal MCE at TC and the antiferromagnetic coupling between the Sm 4f and Mn 3d moments is most likely responsible for the inverse MCE below Tg. The co-existence of normal and inverse MCEs is technologically potential and interesting as the sample can be cooled by adiabatic magnetization and demagnetization in different temperature regions enhancing the refrigeration capacity.

Influence of Ce addition on the structural, magnetic, and magnetocaloric properties in La0.7−xCexSr0.3MnO3 (0≤x≤0.3) ceramic compound

We report improvement in the magnetocaloric properties of Ce-doped lanthanum manganites. Polycrystalline La0.7−xCexSr0.30MnO3 (0≤x≥0.3) samples were prepared using the conventional solid-state reaction method with phase purity and structure confirmed using X-ray diffraction. Temperature dependent magnetization measurements and Arrott analysis reveal second order ferromagnetic transition in parent sample and as well as in doped sample with Curie temperature decreasing progressively with increasing Ce-concentration from ~370K for x=0.0 to 310K for x=0.30. Magnetic entropy change (ΔSM) was calculated by applying the thermodynamic Maxwell equation to a series of isothermal field dependent magnetization curves. A large ΔSM associated with the ferromagnetic–paramagnetic transition in La0.7−xCexSr0.30MnO3 samples has been observed. The value of ΔSM was found to increase with Ce-doping up to x=0.15 and the highest value of 2.12Jkg−1K−1 (at ΔH=2T) was observed for La0.55Ce0.15Sr0.30MnO3 sample near the Curie temperature of 356K. Also, improved relative cooling power of ~122Jkg−1 was observed for the same sample. Due to the large magnetic entropy change and high Curie temperature, the La0.55Ce0.15Sr0.30MnO3 sample is suggested to be used as potential magnetic refrigerants for magnetic refrigeration technology above room temperature.

A family of Fe(3+) based double-stranded helicates showing a magnetocaloric effect, and Rhodamine B dye and DNA binding activities.

Herein, the synthesis, structural characterization, magnetic properties and guest binding activities of four Fe(3+) based double-stranded helicates namely; [Fe2(L)2](ClO4)(Cl)·4(CH3OH)·2(H2O) (), [Fe2(L)2](BF4)2·2(H2O) (), [Fe2(L)2](NO3)2·3(CH3OH)·2(H2O) (), and [Fe2(L)2](Cl)2·2(CH3OH)·4(H2O) () are reported. Complexes have been synthesized using the hydrazide-based ligand H2L (H2L = N'1,N'4-bis(2-hydroxybenzylidene)succinohydrazide) and the corresponding Fe(2+) salts. Each of the independent cationic complexes [Fe2(L)2](2+) shows double-stranded helicates from the self-assembly of the ligand and metal ions in a 2 : 2 ratio, where the individual Fe(3+) centre is lying on a C2-axis and the ligand strands wrap around it. In , ligand L adopts "pseudo-C" conformations and forms a double-stranded dinuclear helicate with a small cage in between them. Moreover, in , each of the independent cationic complexes [Fe2L2](2+) is inherently chiral and possesses P for right-hand and M for left-hand helicity and as a consequence is a racemic solid. Detailed magnetic studies of all the complexes reveal that the Fe(3+) centres are magnetically isolated and isotropic in nature. Estimation of the Magnetocaloric Effect (MCE) from magnetization data unveils a moderate MCE at a temperature of 3 K with magnetic entropy changes (-ΔSm) of 22.9, 27.7, 24.1, 26.5 J kg(-1) K(-1) at a magnetic field of 7 T for complexes , respectively. Also, the variation of the -ΔSm values was justified by considering the parameter of magnetization per unit mass. Stability of all the complexes in solution phase was confirmed by ESI-mass spectrometric analysis and liquid phase FT-IR spectroscopy. Further, the interaction of the complexes with Rhodamine B dye was examined by UV-vis and fluorescence spectroscopic study. The observed blue-shift in the fluorescence study and hyperchromicity and hypochromicity with the appearance of two isosbestic points in the UV-vis study ascertain the interactions of the dye with the complexes. A DNA binding study by absorption spectral titration suggests the weak external intercalation of complex within the nucleotide of calf thymus DNA. Computational study supports the isotropic nature of the metal centres and the consequent high spin multiplicity, which assists the complexes to show significant magnetic entropy changes.

Effect of Cerium Doping on Crystal Structure and Magnetic Properties of La<sub>1−</sub><i><sub>y</sub></i>Ce<i><sub>y</sub></i>Fe<sub>11.44</sub>Si<sub>1.56</sub> Compounds

Crystal structure and magnetic properties of Cerium-doped La1−yCeyFe11.44Si1.56 (y = 0.0 − 0.3) compounds are reported. The compounds possess the NaZn13-type cubic structure with ferromagnetic arrangement. The substitution of Ce into the host lattice slightly decreased the lattice constant from 1.1477 to 1.1471 Å, and as the doping content increased, the saturation magnetization and Curie temperature of the samples were also reduced. A large value of the magnetic entropy change ΔSm was observed at low doping concentration.

Luminescence, magnetocaloric effect and single-molecule magnet behavior in lanthanide complexes based on a tridentate ligand derived from 8-hydroxyquinoline.

A new family of lanthanide complexes, [Ln2(hfac)4L2] (Ln = Eu (1), Gd (2), Tb (3), Dy (4), Ho (5), Er (6), Lu (7); hfac = hexafluoroacetylacetonate, HL = 2-(2′-benzothiazole)-8-hydroxyquinoline), was synthesized and characterized using single-crystal X-ray diffraction, elemental analysis (EA), thermal gravimetric analysis (TGA), powder X-ray diffraction (PXRD) and UV-vis spectra. X-ray crystallographic analyses reveal that 1–7 are isomorphous and crystallize in the monoclinic space group C2/c. In these dinuclear complexes, each LnШ ion is eight-coordinated with two bidentate hfac and two μ-phenol bridging L ligands. The TGA results show that the complexes have relatively high thermal stabilities. Complexes 1 and 3 show the characteristic transitions of the corresponding lanthanide ions with ligand-related emission peaks. Meanwhile, complexes 4 and 7 exhibit ligand-centered fluorescence at room temperature. Magnetic measurements were carried out on complexes 2–6. The magnetic study reveals that 2 displays a magnetocaloric effect, with a maximum −ΔSm value of 16.89 J K−1 kg−1 at 2 K for ΔH = 8 T. Dynamic magnetic studies reveal single-molecule magnet (SMM) behavior for complex 4. Fitting the dynamic magnetic data to the Arrhenius law gives an energy barrier ΔE/kB = 50.33 K and pre-exponential factor τ0 = 1.05 × 10(-8)s.

Three Isostructural One-Dimensional LnIII Chains with Distorted Cubane Motifs Showing Dual Fluorescence and Slow Magnetic Relaxation/Magnetocaloric Effect

Three new homometallic lanthanide complexes with mixed carboxylate-modified rigid ligands, [Ln(μ3-OH)(na)(pyzc)]n (na(-) = 1-naphtholate, pyzc(-) = 2-pyrazinecarboxylate, Ln = Dy (1), Yb (2), and Gd (3)), were solvothermally synthesized, and their structures and magnetic as well as photophysical properties were completely investigated. Complexes 1-3 are crystallographically isostructural, exhibiting linear chains with four bidentate bridging μ-COO(-) moieties encapsulated cubic {Ln4(μ3-OH)4}(8+) clusters repeatedly extended by 4-fold chelating-bridging-pyzc(-) connectors. Magnetically, the former two complexes with highly anisotropic Dy(III) and weak anisotropic Yb(III) ions in the distorted NO7 triangular dodecahedron coordination environment display field-induced slow relaxation of magnetization. Fitting the dynamic magnetic data to the Arrhenius law gives energy barrier ΔE/kB = 39.6 K and pre-exponential factor τo = 1.52 × 10(-8) s for 1 and ΔE/kB = 14.1 K and τo = 2.13 × 10(-7) s for 2. By contrast, complex 3 with isotropic Gd(III) ion and weak intracluster antiferromagnetic coupling shows a significant cryogenic magnetocaloric effect, with a maximum -ΔSm value of 30.0 J kg(-1) K(-1) at 2.5 K and 70 kOe. Additionally, the chromophoric na(-) and pyzc(-) ligands can serve as antenna groups, selectively sensitizing the Dy(III)- and Yb(III)-based luminescence of 1 and 2 in the UV-visible region by an intramolecular energy transfer process. Thus, complexes 1-3, incorporating field-induced slow magnetic magnetization and interesting luminescence together, can be used as composite magneto-optical materials. More importantly, these interesting results further demonstrate that the mixed-ligand system with rigid carboxylate-functionalized chromophores can be excellent candidates for the preparations of new bifunctional magneto-optical materials.

Large reversible magnetocaloric effect in antiferromagnetic HoNiSi compound

Magnetic properties and magnetocaloric effect (MCE) of intermetallic HoNiSi compound have been investigated systematically. It is found that HoNiSi exhibits antiferromagnetic (AFM) state below the Néel temperature TN of 3.8 K, which is quite close to the liquid helium temperature (4 K). A giant MCE without hysteresis loss is observed in HoNiSi, which is related to the field-induced first-order metamagnetic transition from AFM to ferromagnetic states. For a magnetic field change of 2 T, the maximum values of magnetic entropy change (−ΔSM) and adiabatic temperature change (ΔTad) are 17.5 J/kg K and 4.5 K, respectively. In addition, HoNiSi presents both large values of positive and negative ΔSM for the low field changes, i.e., the maximum −ΔSM values are 9.2 J/kg K around TN and −7.2 J/kg K below TN for the field changes of 1 and 0.5 T, respectively. A universal curve of ΔSM is successfully constructed by using phenomenological procedure, proving the applicability of universal ΔSM curve for AFM materials. The giant reversible MCE for relatively low magnetic field change makes HoNiSi attractive candidate for magnetic refrigerant materials around liquid helium temperature.

Magnetic and magnetocaloric properties of Ho 6 Co 2 Ga-type Dy 6 Co 2.5 Sn 0.5 compound

Abstract DC magnetization studies on Dy6Co2.5Sn0.5 compound (orthorhombic, Ho6Co2Ga-type, space group Immm, No. 71) have been carried out in the temperature range of 2–300 K and in magnetic fields up to 140 kOe. A field induced metamagnetic transition is observed below its Neel point of 42 K (at 2 K the critical field Hc is 37 kOe). Magnetization-field isotherms have been measured for this compound near magnetic transition temperatures from which isothermal magnetic entropy change, ΔSm, has been computed. The maximum ΔSm values of –5.2 J/kg K (for a field change of 80 kOe) and +6.5 J/kg K (for a field change of 50 kOe) are observed at 52 K and 13 K, respectively.

Magnetic properties and magnetocaloric effect at room temperature of Ni50−x Ag x Mn37Sn13 alloys

In this work, we present a detailed study of the magnetic properties and the magnetocaloric effect at room temperature of Ni50−xAgxMn37Sn13 alloys with x = 1, 2, and 4, which were prepared by using an arc-melting method. Experimental results reveal that a partial replacement of Ag for Ni leads to a decrease in the anti-FM phase in the alloys. In addition, the martensitic-austenitic phase transition shifts towards lower temperature and is broaded. The Curie temperature (TCA) for the austenitic phase also shifts toward to lower temperature, but not by much. The Curie temperature was found to be 308, 305, and 298 K for x = 1, 2, and 4, respectively. The magnetic entropy change (ΔSm) of the samples was calculated by using isothermal magnetization data. Under an applied magnetic field change of 10 kOe, the maximum value of ΔSm (|ΔSmax|) was achieved at around room temperature and did not change much (~0.8 J·kg−1·K−1) with increasing Ag-doping concentration. Particularly, the M2 vs. H/M curves prove that all the samples exhibited a second-order magnetic phase transition. Based on Landau’s phase-transition theory and careful analyses of the magnetic data around the TCA, we have determined the critical parameters β, γ, δ, and TC. The results show that the β values are located between those expected for the 3D-Heisenberg model (β = 0.365) and mean-field theory (β = 0.5). Such a result proves the coexistence of short-range and long-range ferromagnetic interactions in Ni50−xAgxMn37Sn13 alloys. The nature of the changes in the critical parameters and the |ΔSmax| is thoroughly discussed by means of structural analyses.

Investigation of multifunctional properties of Mn50Ni40−xCoxSn10 (x = 0–6) Heusler alloys

A series of Co doped Mn50Ni40−xCoxSn10 (x=0, 1, 2, 2.5, 3, 4 and 6) Heusler alloys has been investigated for their structural, magnetic, magnetocaloric and exchange bias properties. The martensitic transition temperatures are found to decrease with the increase in Co concentration due to the decrease in valence electron concentration (e/a ratio). The Curie temperature of austenite phase increases significantly with increasing Co concentration. A large positive magnetic entropy change (ΔSM) of 8.6 and 10.5J/kgK, for a magnetic field change of 50kOe is observed for x=0 and 1 alloys, and ΔSM values decreases for higher Co concentrations. The relative cooling power shows a monotonic increase with the increase in Co concentration. Large exchange bias fields of 920 Oe and 833 Oe have been observed in the alloys with compositions x=0 and 1, after field cooling in presence of 10kOe. The unidirectional anisotropy arising at the interface between the frustrated and ferromagnetic phases is responsible for the large exchange bias observed in these alloys. With increase in Co, the magnetically frustrated phase diminishes in strength, giving rise to a decrease in the exchange bias effect for larger Co concentration. The exchange bias fields observed for compositions x=0 and 1, in the present case are larger than that reported for Co doped Ni–Mn–Z (Z=Sn, Sb, and Ga) alloys. Temperature and cooling field dependence of the exchange bias field and coercivity have been related to the change in the unidirectional anisotropy. This study shows that an optimum Co doping results in the tuning and enhancement of the multifunctional properties in Mn rich Ni–Mn–Sn alloys.

New magnetocaloric material based on GdNiH3.2 hydride for application in cryogenic devices

AbstractThe paper presents the investigation of GdNiH3.2 hydride magnetocaloric properties. The isothermal magnetization in the fields up to 5 T and heat capacity data are obtained for GdNiH3.2 and GdNi compounds. The maximum value of magnetic entropy change ΔSM in GdNiH3.2 is extremely large and obtained in much lower temperature range compared to GdNi.It is shown that the hydrogenation does not noticeably affect the value of ΔSM but shifts ΔSM(T) maximum to lower temperatures (∼ 11K). The possibility of GdNiH3.2 application in cryogenic devices is discussed.(© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Nearly constant magnetic entropy change and adiabatic temperature change in PrGa compound

The magnetic properties and magnetocaloric effect (MCE) of PrGa compound are studied in detail. Both thermomagnetization curves and heat capacity curves indicate that PrGa compound undergoes a transition from ferromagnetic (FM) to antiferromagnetic (AFM) phase at Tt ∼ 27 K and a transition from AFM to paramagnetic (PM) phase at T0 ∼ 37 K with increasing temperature. As the applied field increases, the magnetic state between Tt and T0 shows an obvious metamagnetic transition from AFM to FM state. The magnetic entropy change (ΔSM) calculated from magnetic property measurement and that obtained from heat capacity measurement are in good agreement with each other above 25 K. Instead of peak like distribution, nearly constant value of ΔSM in a temperature range from 29.5 K to 37.5 K is observed when the field change is 0–5 T. The adiabatic temperature change (ΔT) also shows similar change rules. This characteristic of MCE is very important for the practical applications of magnetic refrigerant materials.

Iron Lanthanide Phosphonate Clusters: {Fe6Ln6P6} Wells—Dawson-like Structures withD3dSymmetry

Reaction of [Fe3(μ3-O)(O2C(t)Bu)6(HO2C(t)Bu)3](O2C(t)Bu) and [Ln2(O2C(t)Bu)6(HO2C(t)Bu)6] (Ln = lanthanide) with three different phosphonic acids produce a family of highly symmetrical {Fe6Ln6P6} clusters with general formula [Fe6Ln6(μ3-O)2(CO3)(O3PR)6(O2C(t)Bu)18], where R = methyl 1, phenyl 2, or n-hexyl 3. All the clusters present an analogous metal frame to the previously reported {Ni6Ln6P6} both being related to the well-known Wells-Dawson ion from polyoxometallate chemistry. These highly symmetrical clusters have, or approximate very closely to, D3d point symmetry. Both Fe(III) and Gd(III) ions are magnetically isotropic and could thus exhibit promising magnetocaloric properties; hence we investigated the {Fe6Gd6P6} compounds accordingly. Modeling the magnetic data of [Fe6Gd6(μ3-O)2(CO3)(O3PPh)6(O2C(t)Bu)18] by the finite-temperature Lanczos method gave a strong antiferromagnetic Fe···Fe interaction (J(Fe-Fe) = -30 cm(-1)) and very weak Gd···Gd and Gd···Fe exchange interactions (|J| < 0.1 cm(-1)). The strong antiferromagnetic Fe···Fe interaction could account for the relatively smaller -ΔSm value observed, compared against the {Ni6Gd6P6} analogues.

The influence of quench atomic disorder on the magnetocaloric properties of Ni–Co–Mn–In alloys

The magnetocaloric effect in Ni–Co–Mn–In alloys is studied at low magnetic field, across the first order magnetostructural transition. The Co doping at Ni site induces the large magnetic entropy change (ΔSm) above room temperature. The large ΔSm of 11J/KgK has been observed for disordered Ni1.81Co0.22Mn1.46In0.51 alloy at 337K at an applied field of 1.5Tesla. The influence of quench atomic disorder on the magnetocaloric properties of Ni–Co–Mn–In alloys has been studied. The atomic disorder significantly increases the peak value of ΔSm and decreases the peak width. The refrigeration capacity (RC) is almost unchanged with atomic disorder.