Conventional Magnetocaloric Effect Research Articles

Influence of Ge-doping on the collinear and non-collinear antiferromagnetic phases of Mn[formula omitted]Si[formula omitted] alloy

Effect of Ge-doping at the non-magnetic site (Si-site) of the Mn-based binary alloy Mn5Si3 has been explored through temperature-dependent x-ray diffraction, dc-magnetic, and electrical transport measurements. All the doped alloys show D88 type hexagonal structure with space group P63/mcm at room temperature and undergoes two structural distortions, hexagonal (P63/mcm) → orthorhombic (Ccmm) → orthorhombic (Cc2m), on cooling. The magnetic characters of these orthorhombic (Cc2m), orthorhombic (Ccmm), and hexagonal (P63/mcm) phases are non-collinear antiferromagnetic (AFM1), collinear antiferromagnetic (AFM2), and paramagnetic (PM), respectively. Doping of Ge results in a significant increase in the AFM1 to AFM2 transition temperature (TN1). However, the AFM2 to PM transition point remains unchanged. In addition, a reasonable increase in the critical field values of the AFM1 to AFM2 transition via another non-collinear antiferromagnetic phase (AFM1′) with increasing Ge concentration has been observed, indicating the strengthening of AFM1 and AFM1′ phases over the AFM2 phase. Such behaviors make the observation of unusual magnetic properties of undoped Mn5Si3 alloys, like inverted hysteresis loop (IHL) and thermomagnetic irreversibility (TI), more evident for these Ge-doped alloys. Further, this study unfolds the presence of conventional and inverse magnetocaloric effect and they found to decrease with Ge doping. An interesting interplay for positive and negative magnetoresistance has also been observed in all the studied alloys.

Exploring complex magnetic phase transitions and magnetocaloric effect in the nanocrystalline Nd0.5Ca0.5MnO[formula omitted] compound

In this article, we have investigated the temperature and magnetic field-induced complex magnetic phases and magnetocaloric properties of the nanocrystalline Nd0.5Ca0.5MnO3 (NCMO) compound in detail. The compound exhibits charge-ordered antiferromagnetic (CO-AFM) and charge-orbital-ordered antiferromagnetic (AFM) phases at TCO≃ 225 K and TN= 160 K respectively. At the intermediate temperature range, i.e. TN≤ T ≤ TCO, an unfamiliar magnetic state is present where the orbital ordering of manganese ions sets progressively. Both the short-range and zig-zag ordered ferromagnetic (FM) chains and an AFM phase coexist within this temperature window. The effect of magnetic field and temperature drastically modifies the fragile magnetic ground state and this change is also reflected in the magnetocaloric properties of the studied compound. At the low-temperature region, an inverse magnetocaloric effect (MCE) is noticed due to the kinetically arrested magnetic moments of the AFM phase. However, a conventional MCE is noticed in the high-temperature regime. The anomalous behavior of the MCE in the nanocrystalline NCMO compound is analyzed by considering the effect of the reduction of particle size and the meta-stable nature of the magnetic ground state. In addition, we have paid attention to the hysteretic losses associated with the first-order phase transition (FOPT) in order to estimate the magnetic cooling capacity for the material. These studies carry notable importance for the usefulness of nanocrystalline half-doped manganite compounds not only for basic scientific research purpose, but also having possible practical utilization in the magnetic refrigeration industries.

Large conventional and inverse magnetocaloric effects in RE2Ga2Mg (RE = Tm, Er, Ho) compounds

The Mo2FeB2-type compounds RE2Ga2Mg (RE = Tm, Er, Ho) (space group P4/mbm) exhibit a large magnetocaloric (MC) effect which makes them promising for use in cryogenic magnetic cooling applications. They exhibit low temperature metamagnetic nature below their Néel temperatures of 6.8, 11.7 and 18.4 K for Tm2Ga2Mg, Er2Ga2Mg and Ho2Ga2Mg, respectively. The magnetic entropy change, the temperature-averaged entropy change (3 K-lift), and the relative cooling power under a magnetic field change of 0–7 T are 15.6, 15.4 J/kgK and 275.8 J/kg for Tm2Ga2Mg; 13.2, 13.0 J/kgK and 268.0 J/kg for Er2Ga2Mg; as well as 9.1, 9.0 J/kgK and 223.0 J/kg for Ho2Ga2Mg, respectively.

Magnetic and magnetocaloric properties of polycrystalline Pr[formula omitted]Ca[formula omitted]MnO[formula omitted] (x [formula omitted] 0.85, 0.90, 0.95) compounds: Emergence of large inverse and conventional magnetocaloric effects

Magnetic and magnetocaloric effect have been investigated for the electron doped polycrystalline Pr1−xCaxMnO3 (x ∼ 0.85, 0.90, 0.95) compounds. The experimental outcomes indicate that the nature of the ground state is very much sensitive with the doping concentration. Pr0.15Ca0.85MnO3 compound exhibits antiferromagnetic ground state. In contrast to that ferromagnetic nature was found for the Pr0.10Ca0.90MnO3 and Pr0.05Ca0.95MnO3 compounds. Although, for x∼0.90 ferromagnetic phase was stable. However for x∼ 0.95, the ferromagnetic state is quite unstable. Additionally for the doping concentration x∼ 0.95, the anomalous nature was found in temperature dependent coercivity. Magnetocaloric effect study indicate that antiferromagnetic Pr0.15Ca0.85MnO3 compound exhibits large inverse magnetocaloric effect (10.5 J/kg-K at H = 70 kOe magnetic field). On the other hand, ferromagnetic Pr0.10Ca0.90MnO3 and Pr0.05Ca0.95MnO3 compounds show conventional magnetocaloric effect. The magnetocaloric entropy change for x∼0.90 compound is significantly large (7.5 J/kg-K at H = 70 kOe magnetic field) and comparable with the other reported magnetic refrigerant materials. Universal master curve for magnetic entropy change have been constructed for all the materials having inverse and conventional magnetocaloric effect by proper scaling of temperature axis.

Leveraging of both positive and negative magnetocaloric effects in ZnFe2O4 layers

The novel magnetocaloric thin film material with a tunable magnetic transition is the cornerstone of magnetic refrigeration, which plays a crucial role in cooling on-chip devices. Zn-ferrite (ZnFe2O4) occupies a significant place due to its interesting grain size-controlled magnetism. In this study, we investigate the magnetocaloric properties of Zn-ferrite layers consisting of a mixture of superparamagnetic (SPM), ferrimagnetic (FiM), and bulk-type antiferromagnetic (AFM) grains. Due to the co-existence of different magnetic grains, a crossover from the conventional magnetocaloric effect (MCE) to the inverse magnetocaloric effect (IMCE) is observed. The magnetic entropy change (-ΔSM) exhibits high-temperature positive values around the Curie temperature (TC) and low-temperature negative values around either the Néel temperature (TN) or blocking temperature (TB). The maximum value of -ΔSM (0.10 J/kg K) is almost double in AFM-dominant samples compared to SPM-dominant samples, while maintaining a relative cooling power (RCP) of 11.57–14.82 J/Kg under applied fields of 0 – 2T. FiM-dominant samples, with a wide working temperature window around room temperature, are suitable for large RCP applications. Thus, the discovery of new IMCE materials like single layers of Zn-ferrite is equally important in the search for suitable conventional MCE materials for magnetic refrigeration devices, which can exhibit multiple -ΔSM and RCP peaks in low and high temperatures.

Investigation of the triple peak magnetocaloric effects of Ni45Mn44Sn11 ribbons

The magnetocaloric effect (MCE) of Ni45Mn44Sn11 ribbons is simulated, with temperatures ranging from nearly 0 K to 313 K. The MCE of these ribbons exhibits triple peak behavior. Amazingly, three co-occurring peaks of both the inverse and conventional MCEs are found, one for each magnetic transition. Except for temperatures between 251 K and 273 K that correspond to an antiferromagnetic transition that shows an inverse MCE, the type of MCE in Ni45Mn44Sn11 ribbons is conventional. Consequently, materials with triple-peak MCE behavior, such as Ni45Mn44Sn11 ribbons, may provide a fascinating opportunity to obtain magnetic cooling over a wider temperature range than with conventional refrigerant materials, particularly Ni45Mn44Sn11 ribbons, which are inexpensive for use in magnetic refrigeration. Therefore, Ni45Mn44Sn11 ribbons are excellent magnetocaloric magnets for wide temperature ranges, including cryogenic and room temperatures.

Detection of two magnetocaloric consecutive peaks in HoCo2

ABSTRACT To simulate the magnetocaloric effect (MCE) of a HoCo2 sample, a phenomenological model (PM) is used. MCE parameters are inferred from PM as the result of modelling for magnetization vs. temperature in 0.5 T. The HoCo2 exhibits two consecutive conventional MCEs with cooling via adiabatic demagnetization. HoCo2 exhibits double peak MCE behaviour. It is recommended that HoCo2 use it as a useful MR material over a temperature range spanning a significant temperature range of 0–140 K. Consequently, HoCo2 is appealing for MR because its MCE spans a wide temperature range, particularly liquefaction of nitrogen and hydrogen.

The magnetocaloric effect of the lanthanide fluorides: Using polarized neutron scattering to probe a magnetocaloric suitable for hydrogen liquefaction

This work reports the competitive magnetocaloric effect of some simple lanthanide fluoride materials with cations with high magnetic anisotropy. Of these, HoF3 is particularly promising due to exhibiting a high magnetocaloric entropy change under modest applied fields at higher temperatures, which only decreases modestly with temperature such that it has the potential for cooling for hydrogen liquefaction. Spin-polarized neutron spectroscopy indicates that its promising conventional magnetocaloric effect is likely due to the presence of ferromagnetic fluctuations of highly anisotropic magnetic moments, while its singlet electronic ground state and low-temperature magnetic ordering lead to a decrease in its magnetocaloric performance below 4 K.

Observation of conventional and inverse magnetocaloric effects in (Dy$$_{0.6}$$Gd$$_{0.4}$$)$$_{5}$$Pd$$_{2}$$

Observation of conventional and inverse magnetocaloric effects in (Dy$$_{0.6}$$Gd$$_{0.4}$$)$$_{5}$$Pd$$_{2}$$

Magnetic properties and universal behaviour of magnetocaloric effect for polycrystalline [formula omitted] compound

In the present study, we have systematically investigated the magnetic and magnetocaloric properties as well as the universal behaviour of magnetocaloric effect (MCE) for polycrystalline (Nd0.5Sm0.5)0.5Sr0.5MnO3 compound. The universal behaviour of magnetic entropy change is proposed here for conventional magnetocaloric effect (CMCE) materials with second order phase transition. Thus, the construction of a universal master curve for MCE is possible in our system by rescaling the temperature axis. For such CMCE compounds, ΔS follows the power law dependence of H: ΔS ∝ Hn where ‘n’ is dependent on both H and T. In this paper, we have studied the universal behaviour of MCE at different conditions of initial and final field values. The result suggests that the universality behaviour of MCE is satisfied if and only if the initial base field remains zero or at a constant value.

Anisotropy of magnetocaloric effect and rotating magnetocaloric effect in 2D coordination polymer based on {CuII[WV(CN)8]}- and adeninium cations

Anisotropy of conventional magnetocaloric effect (MCE) and rotating magnetocaloric effect (RMCE) have been investigated in quasi-two-dimensional coordination polymer (AdeH){CuII[WV(CN)8]}·2H2O with high magnetic anisotropy and topological phase transition. Magnetic entropy changes (ΔSmag) were calculated from magnetic measurements of single crystals in three orthogonal directions, H||a*, H||b and H||c. The highest ΔSmag = 3.49 J K−1 kg−1 was recorded for conventional MCE in the H||c direction for µ0|ΔH|=7.0 T and at a peak temperature of 37.5 K. The RMCE was calculated for the rotation around the b axis by 90° from H||a* to H||c with the maximal ΔSmag of 1.62 J K−1 kg−1 detected for µ0H = 7.0 T at 38 K.

Experimental Study of Magnetocaloric Effect in Tetraaquabis(Hydrogen Maleato)Nickel(II), [Ni(C4H3O4)2(H2O)4]—A Potential Realization of a Spin-1 Spatially Anisotropic Square Lattice with Ferromagnetic Interactions

An experimental study of the magnetocaloric effect in tetraaquabis(hydrogen maleato)nickel(II), [Ni(C4H3O4)2(H2O)4] powder sample is presented. The magnetocaloric properties of the studied sample were investigated using specific heat and magnetization measurements in magnetic fields up to 9 T in the temperature range from 0.4 to 50 K. A large conventional magnetocaloric effect was found at a temperature of about 3.5 K, where −ΔSM = 8.5 Jkg−1K−1 and 11.2 Jkg−1K−1 for a magnetic field of 5 T and 7 T, respectively. Assuming a substantial role of the crystal field, the temperature dependence of the magnetic specific heat in a zero magnetic field was compared with an S = 1 model with single-ion anisotropy parameters D and E (axial and rhombic). The best agreement was found for the parameters D/kB = −7.82 K and E/kB = −2.15 K. On the other hand, the experimental temperature dependence of −ΔSM shows higher values compared to the theoretical prediction for the mentioned model, indicating the presence of additional factors in the system, such as an exchange interaction between magnetic ions. The first exchange pathway can be realized through maleic rings between the nearest Ni(II) ions. The second exchange pathway can be realized through water molecules approximately along the a crystallographic axis. Broken-symmetry DFT calculations performed using the computational package ORCA provided the values of ferromagnetic exchange interactions, J1/kB = 1.50 K and J2/kB = 1.44 K (using B3LYP functional). The presence of such ferromagnetic correlations in the studied system may explain the enhanced magnetocaloric effect compared with the model of an anisotropic spin-1 paramagnet.

From conventional to inverse magnetocaloric effect in GdMn1-x Cr x O3

In this work, a phenomenological model (PM) is used to simulate the magnetocaloric effect (MCE) of GdMn1-x Cr x O3 (0 ≤x ≤0.4) (GMCO) samples through the modelling of experimental isofield thermo-magnetization curves. The results showed that the MCE of GMCO samples depends strongly on Cr content, achieving a conventional MCE for low Cr content (level of doping x ≤ 0.3). However, the MCE of a higher Cr content sample has an inverse MCE. The behaviour of MCE in GMCO samples indicated that GMCO compounds are interesting magnetocaloric materials and can fruitfully be functioned as cryogenic magnetic refrigerants below 40 K especially in radiation detectors for outer space research.

Magnetic, magnetodielectric, and magnetocaloric properties of new polar oxides RCrWO6 (R = Sm, Eu, Gd, and Tb)

We report new magnetic oxides RCrWO6 (R = Sm, Eu, Gd, and Tb) crystallizing in the polar orthorhombic structure (Space Group: Pna21), where edge-shared dimers of CrO6 and WO6 octahedra are connected by sharing corners and establish a three-dimensional framework. All these compounds exhibit antiferromagnetic ordering of Cr3+ spins at TN ∼ 28–32 K, except SmCrWO6, which shows weak ferromagnetism below TN = 32 K. Isothermal magnetization curves of RCrWO6 (R = Gd and Tb) at low temperatures show field-induced metamagnetic transition. Further, a dielectric anomaly at TN in all these compounds evidences the magnetodielectric effect. In addition, GdCrWO6 demonstrates magnetocaloric effect (MCE) with a maximum magnetic entropy change of 9.22 J kg−1K−1 at 70 kOe with relative cooling power (RCP) ∼ 101 J kg-1. On the other hand, TbCrWO6 exhibits both conventional and inverse magnetocaloric effects with significant entropy change and RCP.

The Inverse and Conventional Magnetocaloric Effects in Ni0.4Cu0.2Zn0.4Fe2-xDyxO4 Nanoferrites Over an Extraordinary Temperature Range

The magnetocaloric effect (MCE) of Ni0.4Cu0.2Zn0.4Fe2-xDyxO4 (x = 0.02, 0.03, and 0.04) nanoferrites is simulated using a phenomenological model. The analysis indicates that the MCE of Ni0.4Cu0.2Zn0.4Fe2-xDyxO4 nanoferrites is strongly influenced by Dy content in both conventional and inverse MCE. For conventional MCE, the full-width at half-maximum (delta {text{T}}_{{{text{FWHM}}}}) has significant values, ranging between 200 K and 258 K for Ni0.4Cu0.2Zn0.4Fe2-xDyxO4 nanoferrites. However, for inverse MCE, delta {text{T}}_{{{text{FWHM}}}} ranges between 25 and 55 K. The MCE of the Ni0.4Cu0.2Zn0.4Fe2-xDyxO4 system covers an extensive temperature range and is a particularly interesting prospect for nitrogen and hydrogen liquefaction.

Large magnetocaloric effect in antiferromagnetic ternary carbide Dy2Cr2C3 around liquid hydrogen temperature

Field-induced magnetic transitions with large magnetization difference and mitigated thermal loss are highly desirable for the development of magnetocaloric materials used for magnetic refrigeration. Here, we report the magnetocaloric effect (MCE) in antiferromagnetic carbide Dy2Cr2C3. Both the inverse MCE (with positive magnetic entropy change ΔSM) and conventional MCE (with negative ΔSM) have been observed, which are attributed to a field-induced first-order metamagnetic transition from antiferromagnetic to ferromagnetic state and a second-order ferromagnetic to paramagnetic transition, respectively. A maximum -ΔSM of 13.5 J/kg K at 27 K for a field change of 5 T, and correspondingly a refrigerant cooling power of 315 J/kg in a wide working temperature span of 31 K have been achieved. Such a remarkable magnetocaloric response, together with the minor magnetic hysteresis of less than 0.02 T, indicate that Dy2Cr2C3 carbide could be a promising candidate refrigerant for magnetic refrigeration working at temperatures near the liquid H2.

Conventional and inverse magnetocaloric and electrocaloric effects of a mixed spin-(1/2, 1) Heisenberg dimer

Conventional and inverse magnetocaloric and electrocaloric effects of a mixed spin-(1/2, 1) Heisenberg dimer

Cd-doping effects in Ni–Mn–Sn: experiment and ab-initio study

Martensitic transformation (MT), magnetic properties, and magnetocaloric effect (MCE) in Heusler-type Ni47Mn40Sn13−x Cd x (x= 0, 0.75, 1, 1.25 at. %) metamagnetic shape memory alloys (MetaMSMAs) are investigated, both experimentally and theoretically, as a function of doping with Cd. Ab-initio computations reveal that the ferromagnetic (FM) configuration is energetically more favorable in the cubic phase than the antiferromagnetic (AFM) state in undoped and doped alloys as well. Moreover, it is revealed that the alloys in the ground state exhibit a tetragonal structure confirming the existence of MT, in agreement with the experiments. It was indicated, both in theory and practice, that a reduction of the unit cell volume and an increase of the MT temperature as a function of the Cd doping. Indirect estimations of MCE in the vicinity of MT were carried out by using thermomagnetization curves measured under different magnetic fields up to 5 T. The results demonstrated that the doped alloys exhibit enhanced values of the inverse MCE comparable with those of Ni-Mn-based MetaMSMAs. Maximum magnetic entropy change in a field change of 2 T increases from 3.0 for the undoped alloy to 3.4 and 5.0 for the alloys doped with 0.75 and 1 at.% of Cd, respectively. The inverse and conventional MCE were explored by direct measurements of the adiabatic temperature change under the magnetic field change of 1.96 T. The Cd doping increased the maximum of inverse MCE by nearly 78% from 0.9 K to 1.6 K for the undoped and doped alloys, respectively. The results depicted that Cd doping can effectively tailor the structural, magnetic, and MCE properties of the Ni–Mn–Sn MetaMSMAs.

Sn-doping induced modification of the magnetic and magnetocaloric properties in MnNiGe alloy

Sn-doped MnNiGe alloy of nominal composition MnNiGe0.915Sn0.085 has been examined through structural and magnetic investigations. Sn-doping stabilizes the hexagonal structure (with P63/mmc space group) at room temperature. On cooling from room temperature, it first orders antiferromagnetically (with commensurate structure) around 185 K. Further cooling results in a structural change of martensitic type around 145 K. The observed structural transition is also found to be associated with a simultaneous magnetic transition from high temperature commensurate antiferromagnetic state to low temperature incommensurate antiferromagnetic state. Both conventional and inverse magnetocaloric effect (MCE), with peak values of −6.01 J/kg-K and 6.56 J/kg-K for 0 to 5 tesla of changing magnetic field, have been visible around the magnetic and structural transitions, respectively. A significant effect of external hydrostatic pressure on the magnetic and MCE behaviors has also been observed.

Investigation of field-controlled magnetocaloric switching and magnetodielectric phenomena in spin-chain compound Er2BaNiO5

The Haldane spin-chain compound Er2BaNiO5 has been known to possess magnetoelectric coupling below the magnetic ordering temperature. Here we report various low-temperature magnetic and magnetocaloric properties, and magnetodielectric (MD) effect above magnetic ordering temperature in this compound. The present compound displays a coexistence of conventional and inverse magnetocaloric effects with a large entropy change of 5.9 and −2.5 J kg−1 K−1, respectively. Further, it exhibits a remarkable switching between them, which can be tuned with temperature and magnetic field. In addition, evolution of two magnetic field-dependent metamagnetic transitions at 19.7 and 27.7 kOe, and their correlation with magnetocaloric switching effect, make this compound effective for potential applications. On the other hand, demonstration of intrinsic MD effect (1.9%) near and above antiferromagnetic ordering temperature, through a moderate coupling between electric dipoles and magnetic spins, establishes this compound as a useful candidate for future research. A detailed analysis of these findings, in a framework of different magnetic interactions and magnetocrystalline anisotropies, is discussed here. Overall, these results may provide a future pathway to tune the magnetic, MD, and magnetocaloric properties in this compound toward better application potential.