Room Temperature Magnetocaloric Effect Research Articles

Extraordinary mechanical properties and room-temperature magnetocaloric effects in spark plasma sintered all-d-metal Ni-Co-Mn-Ti alloy

The all-d-metal Ni-Co-Mn-Ti Heusler alloy is a promising candidate for magnetic refrigeration application because of its considerable magnetocaloric effect and excellent mechanical properties. In this study, the influence of powder particle size on the martensitic transformation, magnetic and mechanical properties of Ni37Co13Mn34Ti16 spark plasma sintered samples have been investigated. It was found that the martensite transformation temperature was shifted to a higher value, while the mechanical properties decreased significantly with an increase in particle size. The sintered sample (S1) with a particle size of 0–15 μm exhibited enhanced characteristics such as thermal effect, magnetic and mechanical properties. The S1 martensitic transformation temperature occurred near ambient temperature, and the sample exhibited the maximum magnetic entropy changes as high as 37.53 J·kg−1·K−1 under a 5 T magnetic field. Moreover, the associated compressive fracture stress and strain were 2129 MPa and 27.78%, respectively, representing an 88.6% and 104.3% increase relative to the as-cast sample.

The Effect of Fe Addition on the Curie Temperature and Magnetic Entropy of the Gd45Co50Al5 Amorphous Alloy.

The new magnetic refrigeration (MR) technology, which uses the magnetocaloric effect (MCE) of materials for refrigeration, has shown apparent advantages over the compression refrigeration of freon and other gases. Therefore, how to obtain materials with excellent magnetic entropy change near room temperature is of great significance for the realization of MR. In order to achieve high Tc of a Gd-based amorphous alloy, Gd45Co50Al5 amorphous alloy with good room temperature MCE was selected, and a series of Gd45Co50-xFexAl5 (x = 2, 5, 10) amorphous alloys were prepared by adding Fe instead of Co. In this paper, the effect of Fe addition on the Curie temperature, and the magnetic entropy change in the alloys, were studied thoroughly. The results show that the Curie temperature is increased to 281 K by adding 5% Fe elements, which is mainly related to the enhanced 3d-3d interaction of transition elements caused by Fe addition, and the maximum value of magnetic entropy change is 3.24 J/(kg·K) under a field of 5 T. The results are expected to provide guidance for further improving the room temperature MCE of Gd-based amorphous alloys.

Critical behavior and room temperature magnetocaloric effect of La-doped Pr0.7Sr0.3MnO3 compounds

In this work, we present the critical and the magnetocaloric properties of Pr0.7-xLaxSr0.3MnO3 compounds around room temperature. The samples exhibit a single phase with an orthorhombic structure. However, the lattice parameters increase with an increase in La content (x). The Curie temperature (TC) of the ferromagnetic (FM)-paramagnetic (PM) phase transition of compounds increases from 256 K for x = 0–319 K for x = 0.3. We observed a large magnetocaloric effect with high maximum magnetic entropy change (|ΔSmax|) values occurring around room temperature, corresponding to |ΔSmax| = 6.65 and 5.21 J/kgK under a magnetic field change (ΔH) of 50 kOe for x = 0.2 and 0.3, respectively. We also pointed out that the change in |ΔSmax| obeys an exponential function of ΔH (|ΔSmax| ∼ ΔHn), where the value of field exponent (n) is approximately 0.52. Furthermore, the critical behavior around TC for compounds with x = 0.2 and 0.3 has been investigated. The results indicate that these compounds undergo a second-order phase transition with the critical parameters (β = 0.311, γ = 1.137, and δ = 4.656 at TC = 298.4 K for x = 0.2; and β = 0.319, γ = 1.098, and δ = 4.442 at TC = 318.7 K for x = 0.3) that are quite close to those expected for the 3D-Ising model. This suggests the existence of the short-range magnetic interactions in these compounds.

Room temperature magnetocaloric effect and electrical transport properties of Co50Fe7V25Ga18Heusler alloys undergoing martensitic transformation

The metamagnetic martensitic transformation from the ferromagnetic austenite phase to the paramagnetic martensite phase was excited in the Co50Fe7V25Ga18 Heusler alloy near room temperature. Accompanying the transformation, the alloy exhibits a good magnetocaloric effect near room temperature with a cooling capacity of 17.02 J/kg under 3 T magnetic field at 302 K and the cusp-type anomalous of the resistivity with the magnetoresistance effect of ∼ 2.27% under a 3 T magnetic field. The power law equations for the temperature dependence of resistivity indicates the actuality of half-metallic properties. Our experimental results indicate that Co50Fe7V25Ga18 Heusler alloy is likely to become a potential candidate for room-temperature magnetic refrigeration and magnetic sensors applications.

Near room temperature magnetocaloric effect of Cr1−xRuxO2 (x = 0.000, 0.125, and 0.250) for magnetic refrigeration

Near room temperature magnetocaloric effect of Cr1−xRuxO2 (x = 0.000, 0.125, and 0.250) for magnetic refrigeration

Magnetic critical behavior and room temperature magnetocaloric effect in Ba1.9Pr0.1FeMoO6 double perovskite compound

In this paper, we report the critical behavior related to the magnetocaloric effect of Ba1.9Pr0.1FeMoO6 double perovskite. A maximum magnetic entropy change, |ΔSMmax| ∼ 0.68 Jkg−1K−1 and relative cooling power, RCP ∼ 62 Jkg−1 were observed under applied field of H = 2.5 T. The critical exponents were evaluated by using modified Arrott plots, Kouvel-Fisher, critical isotherm analysis and Widom scaling relation methods. A second order phase transition (paramagnetic to ferromagnetic) was observed at Curie temperature, TC = 319.73 K with critical exponents β = 0.45, γ = 0.84, and δ = 2.91. The value of these critical exponents shows that this sample obeys mean field model and Widom scaling relation. Also, we observed that the different isothermal magnetization data are able to collapse into the two branches below and above TC based on the single scaling equationM(H,ε)=εβf±(H/εβ+γ) that affirms the authenticity of the critical exponents.

Magnetocaloric Effect in Lightly‐Doped Fe5Si3 Single Crystals

AbstractDevelopment of promising new materials for above room temperature magnetic cooling applications relies on careful balancing of structure and composition to maximize accessible metastable phases that can drive a strong magnetocaloric effect (MCE). However, the working temperatures of these materials may fall outside of desired application windows. In this work, it is shown that it is possible to control metastable phase stability temperatures of Fe5Si3 through selection of appropriate spin and charge doping. Here, the parent material's desired structure appears only within a narrow temperature range from 1098 to 1303 K. Doping with Mn and P is shown to allow stabilization of the parent's high temperature phase and resulting MCE to room temperature. The structural and magnetic properties, and the magnetocaloric effect of single crystal Fe4.83Mn0.16Si2.91P0.09 (FMSP) are investigated experimentally and theoretically. A first‐order magneto‐elastic transition is observed at 348 K, where magnetic onset is accompanied by a change in lattice volume without an apparent change in crystal symmetry. Although the trace Mn and P doping are found to decrease the TC, the maximum magnetic entropy change ΔSMax(T) and the relative cooling power (RCP) of FMSP are enhanced compared to polycrystalline Fe5Si3. As a result, an intrinsically broader entropy change over a larger temperature span is generated in the lightly doped single crystal of Fe5Si3. The magnetic moment of the system is also enhanced. Density functional theory (DFT) calculations are performed to gain microscopic insights into the experimental findings. The results suggest that the hexagonal Fe5Si3 is a new giant room temperature MCE material that is on par with La–Fe–Si and Fe‐Mn‐P‐Si systems.

Ni48Ag2Mn37In13 multifunctional alloy: A room temperature inverse magnetocaloric and magnetoresistive material

An off-stoichiometric Ni-Mn-In Heusler alloy has been synthesized and studied for its magnetocaloric and magnetoresistive capabilities. Ni48Ag2Mn37In13 polycrystalline alloy has co-existing austenite and martensite phases at room temperature. On cooling the alloy from 400 K, austenite phase orders ferromagnetically at 312 K closely followed by a martensite transition around 309 K (in 0.01 T). This alloy in martensite state exhibits antiferromagnetism when the applied field is small, and as the field is increased, it attains ferromagnetic state. A metamagnetic transition is seen in isothermal magnetization near martensite transformation temperature yielding negative sloped-Arrott curves. The second order nature of the austenite-ferromagnetic transition is evidenced from local exponent (n) behavior. The entropy change is moderate around this transition and large around martensite transition which is of first order. Clausius-Clapeyron equation is used to validate the entropy change estimated from Maxwell relation. Resistivity falls acutely as the alloy transits from highly resistive martensite to highly conductive austenite phase. The magnetic field reduces the resistivity of both phases leading to a large negative magnetoresistance. Room temperature magnetocaloric effect and large magnetoresistance with low thermal and magnetic hysteresis are salient features of Ni48Ag2Mn37In13 alloy.

Room temperature magnetocaloric effect in CrTe1−xSex alloys

In this work, we report room temperature magnetocaloric properties in CrTe1−xSex (0.00 ≤ x ≤ 0.10) alloys prepared by a conventional solid-state reaction. The Rietveld refinement of the XRD pattern of CrTe1−xSex showed the emerging of pure hexagonal NiAs structure with P63/mmc (194) space group with increasing Se substitution. Upon μ0H = 5 T applied magnetic field, the magnetocaloric effect analysis revealed maximum magnetic entropy change $$(\Delta {S}_{M})$$ in the range 7.9–9.2 J/kg K−1 with a relative cooling power (RCP) value of about 550–694 J/kg. The RCP values exceed the corresponding RCP value of the prototype Gd element near room temperature. The obtained results suggest that CrTe1−xSex (0.00 ≤ x ≤ 0.10) alloys is a viable candidate for a room temperature magnetic cooling application.

Development of Fe-based amorphous alloy with high iron content for room-temperature magnetic refrigeration application

In this work, in order to develop new Fe-based amorphous alloys with room-temperature magnetocaloric effect and good magnetocaloric performance, high iron content Fe-based amorphous alloys were designed, and their Curie temperatures were adjusted to room temperature through the addition of Mo. As a result, a new Fe83Mo6Si1B7P2C1 amorphous alloy with room-temperature magnetocaloric effect was successfully prepared by melt-spinning technique, and it has the Curie temperature of 300 K, the maximum isothermal magnetic entropy change of 2.74 J kg−1 K−1 and the refrigerant capacity of 485.2 J kg−1 under an applied magnetic field of 5 T. Combining with the advantages of excellent magnetocaloric properties, negligible hysteresis loss, and low material cost, the present Fe83Mo6Si1B7P2C1 amorphous alloy should be a promising candidate as room-temperature magnetic refrigerants.

Spin-Glass-like State and Reversible Room-Temperature Magnetocaloric Effect in Double Distorted Perovskites Nd(Cu3-xMnx)Mn4O12.

The preparation, complex magnetic properties and room-temperature magnetocaloric effect in Nd(Cu3-xMnx)Mn4O12 with cation distribution (Nd3+)A(Cu3-x2+xMnx3+)A'(Mn1+x3+Mn3-x4+)BO122- (x = 1 and 1.5) have been reported. Both compounds show a sharp paramagnetic-ferromagnetic (FM) transition at TC of 300 and 280 K, respectively. The substitution of Cu by Mn at the A' site induces the emergence of a spin glass state below ≈63 K for x = 1 and ≈72 K for x = 1.5 compound. Another antiferromagnetic-like magnetic transition is also observed in both compounds at 23 and 28 K, respectively, which is discussed as the antiferromagnetic coupling between Nd3+ at the A' site and (Mn3+/Mn4+) at the B site. These two compounds exhibit room-temperature magnetocaloric effect. For a small field of 2 T, the maximum magnetic entropy changes -ΔSM are 1.5 J/kg K at 300 K and 1.4 J/kg K at 280 K, respectively. Moreover, the -ΔSM(T) curves show an asymmetric distribution, resulting in high refrigerant capacity values for both compounds. We further demonstrate the distinct roles of the A'- and B-site spins on the magnetic properties and the origin of the spin-glass-like state in double distorted perovskites Ln(Cu3-xMnx)Mn4O12 family of compounds.

Ising critical behavior and room temperature magnetocaloric effect in itinerant ferromagnetic Mn5Ge2.9Fe0.1 compound

In this work, a novel polycrystalline Mn5Ge2.9Fe0.1 compound has been prepared and a detailed analysis on structural, physical and magnetocaloric properties is carried out. Mn5Ge2.9Fe0.1 compound is a second order-itinerant ferromagnet with enhanced Sommerfeld coefficient. The resistivity of this compound is found to show saturation at high temperatures due to spin fluctuations in the compound. Critical behavior analysis has been performed in near-Curie temperature regime and the exponents are estimated. The validity of these exponents is double checked by adopting several scaling hypothesis. The above study however revealed that the magnetic interactions in Mn5Ge2.9Fe0.1 compound is of short-range and comply well with 3D-Ising model. Nevertheless, a modest MCE around room temperature in concert with a substantial temperature width renders Mn5Ge2.9Fe0.1 compound as an appreciable magnetic refrigerant.

Tunable structural and magnetic properties of NiAs-type MnxSb (1.00[formula omitted]x[formula omitted]1.30) compounds

Mn-based alloys can exhibit a variety of magnetic properties related to their tunable exchange interactions. In this work, structural and magnetic properties of hexagonal NiAs-type MnxSb (1.00≤x≤1.30) compounds are studied with a combination of X-ray diffraction, neutron diffraction, and magnetic measurements. It is found that the magnetization, Curie temperature, and magnetocrystalline anisotropy of MnxSb compounds can be tuned by controlling Mn concentration and doping at interstitial (2d) sites. With increasing Mn concentration, magnetic moments of Mn atoms decrease and deviate gradually from the ab-plane to the c-axis for 1.20≤x≤1.22 at room temperature, which leads to a decrease of the Curie temperature Tc and the spin reorientation temperature TSR. By doping with nonmagnetic elements, a substantial room-temperature magnetocaloric effect without magnetic hysteresis was achieved for Mn1.12Zr0.1Sb compound, which is highly beneficial to the practical magnetic refrigeration application.

Room temperature magneto-caloric effect and electron transport properties study on Ni2.14Mn0.55Sb1.31 alloy

Ni2.14Mnd0.55Sb1.3 Heusler alloy has been prepared by the conventional arc melting method with vacuum-sealed annealing. The sample has been crystallized to Fm3¯m space group in L21 phase, and it is the parent crystal structure of the Ni-based Full Heusler alloy. It has been found that the sample has the Curie temperature (para to ferromagnetic transition temperature) at 290K. It was determined from magnetization ∼ temperature plot (M ∼ T) as well as by employing the Arrott plot method. Also, critical exponent analysis by employing the Arrott plot and Kouvel-Fisher methods confirm that the sample (Ni2.14Mn0.55Sb1.31) obeys mean field theory with long range spin ordering. Analysis of temperature dependent resistivity data interestingly reveals the phonon-phonon and magnon-manon scattering dominance above and below the Curie temperature, respectively. The electrical and magnetic properties investigation endorse that there is a correlation between magnetic and electrical properties of the above sample. The magnetocaloric effect (MCE) analysis is carried out by using the Maxwell’s equations in isothermal magnetization data. It is interesting to note that the sample exhibits maximum MCE near the room temperature (∼290K), i.e., the magnetic Curie temperature. Hence the present alloy may be a potential material to be used for magnetic refrigeration application.

The first experimental evidence of room-temperature magnetocaloric effect in fullerenes

The aim of the study was the first characterization of fullerenes, organic molecular solids without a d or f metal/ion, as paramagnets with the magnetocaloric effect (MCE) displayed at the temperatures close to room. Direct determinations of MCE/magnetization thermodynamic parameters and a heat capacity of [60]fullerene (C60) and 1′-N-methyl-2′-(pyridin-4-yl)pyrrolidino[3′,4′:1,2][60]fullerene (PyC60) in aqueous suspensions were performed by means of original microcalorimetric method and differential scanning calorimetry, respectively. Both materials display positive MCE that has been determined to be 0.004 and 0.016 K at 278 K in C60 and PyC60, respectively, when the magnetic induction changes from zero to 1.0 T. The increase in PyC60 MCE is observed despite the fact that the molar heat capacities values of substituted fullerene are two times higher than that of C60. These results along with calculated full energies, bond lengths and a charge on atoms according to Mulliken in fullerenes (PM3 and the Hartree–Fock in the basis of 3-21G, using Gaussian03) are interpreted as a reflection of an aromaticity and antiaromaticity areas state in fullerenes.

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.

Improving the multicaloric properties of Pb(Fe0.5Nb0.5)O3 by controlling the sintering conditions and doping with manganese

Designing multicaloric single-phase materials with combined electro- and magnetocaloric effects is still at its initial stage and presents a number of challenges. One of the main challenges encountered so far is to reduce the excessive electrical conductivity, which leads to the appearance of Joule heating that might completely degrade the electrocaloric response. In this work, multicaloric Pb(Fe0.5Nb0.5)O3 material was successfully prepared exhibiting pronounced electrocaloric effect above room temperature and maximum magnetocaloric effect at cryogenic temperature. The conductivity was suppressed by controlling the sintering temperature. The ceramic sintered at 1000 °C exhibits maximum electrocaloric effective cooling of 0.88 °C at 28 °C and maximum magnetocaloric effect of 0.14 °C at −271 °C. The caloric properties can be further improved by doping Pb(Fe0.5Nb0.5)O3 with manganese. In comparison to the undoped sample, Pb(Fe0.5Nb0.5)O3 doped with 0.5 mol% of manganese exhibits three times higher maxima of electrocaloric effective cooling (2.47 °C at 80 °C) and magnetocaloric temperature change (0.44 °C at −271 °C).

Room temperature magnetocaloric effect and critical behavior in La0.67Ca0.23Sr0.1Mn0.98Ni0.02O3 oxide

The structural, magnetic and magnetocaloric properties of $${\text{La}}_{0.67} {\text{Ca}}_{0.23} {\text{Sr}}_{0.1} {\text{Mn}}_{0.98} {\text{Ni}}_{0.02} {\text{O}}_{3}$$ nano-crystalline manganite are investigated systematically. The compound is elaborated based on Pechini sol–gel method and then annealed at 1000 °C for 24 h. X-ray powder diffraction shows that, the sample crystallizes in a rhombohedral structure with $$R\overline{3} C$$ space group. A magnetization versus temperature study shows that the compound exhibits a second-order magnetic transition from a ferromagnetic to a paramagnetic state at a Curie temperature $$T_{C}$$ = 296 K. To evaluate the magnetic entropy change $$\Delta S_{M}$$ , we measure the magnetization as a function of temperature and magnetic field. At ambient temperature, we find that $${\text{La}}_{0.67} {\text{Ca}}_{0.23} {\text{Sr}}_{0.1} {\text{Mn}}_{0.98} {\text{Ni}}_{0.02} {\text{O}}_{3}$$ sample has a very important magnetocaloric effect (MCE). In a magnetic field variation of 5 T, this MCE is explained by a maximum of magnetic entropy change $$\left| {\Delta S_{M}^{max} } \right|$$ and a big RCP values at 4.92 $${\text{J}}.{\text{Kg}}^{ - 1} {\text{K}}^{ - 1}$$ and 145 J/kg, respectively, around room temperature (296 K), which give the possibility of technologic application in magnetic refrigeration area. In addition, we find an admirable estimate of the magnetic entropy change, which is based on the Landau theory. Finally, we use the magnetic field dependence of $$\Delta S_{M}$$ to determine the critical exponents of the system and we find that β = 0.39, γ = 1.35, and δ = 4.43, are very close to those predicted to the 3D-Heisenberg model. These results indicate that the present compound is one of candidate materials for magnetic refrigerators near room temperature.

New paramagnets based on nanocarbon and cobalt(II)porphyrin: Magnetocaloric effect and specific heat capacity

Abstract This article represents the first unique data about a new paramagnets based on a carbon nanoform composited with cobalt(II) porphyrin with both a photoinduced electron transfer and a room-temperature magnetocaloric effect. Magnetocaloric effect values/magnetization thermodynamic parameters and specific heat capacity have been directly determined for the donor-acceptor triad derived from cobalt(II)5,10,15,20-(tetra-4-tert-butylphenyl)21H,23H-porphyrin and 1′-N-methyl-2′-(pyridin-4-yl)pyrrolidino[3′,4′:1,2][60]fullerene via axial coordination and compared with those for C60 and the precursors. The studies were performed by the original microcalorimetric method developed by us and differential scanning calorimetry. The samples display the positive magnetocaloric effect that has been determined to be equal, to 0.004 (C60), 0.016 (PyC60), 0.028(porphyrin complex), and 0.007 K (triad) at 278 K and 1.0 T. The magnetocaloric effect values observed are comparable with those in metal-based magnetic materials but unlike those, the studied triad demonstrates a photoinduced electron transfer. The contributions of aromatic electron systems to the magnetization thermodynamic parameters have been analyzed.

Magnetic phase transition and room-temperature magnetocaloric effects in (Al,M)Fe2B2 (M = Si, Ga) compounds

Abstract As the emerging ambient low-cost magnetic refrigeration system, the substitution effects on the magnetic properties and magnetocaloric effects in Al1−xSixFe2B2 (x = 0, 0.1, 0.2, 0.3) and Al1−yGayFe2B2 (y = 0.1 and 0.2) have been studied. The single phase is formed in a wide substitution composition region. All phase transitions in these compounds are of second-order and their Curie temperature (Tc) increases with more Si and Ga substitutions. For a field change of 5 T and 7 T, the maximum of entropy change (ΔSmax) of 4.9 J Kg−1 K−1 and 6.3 J Kg−1 K−1 are obtained and not dependent on the Si substitution amount in Al1−xSixFe2B2. As comparison, by Ga substitution, for the field change of 7 T and 5 T, the ΔSmax have been increased to 7.5 J Kg−1 K−1 and 6 J Kg−1 K−1 respectively. The tunable ambient Tc and considerable ΔSmax suggest that AlFe2B2-based compounds are potential low-cost ambient magnetic refrigeration candidates.