Inverse Magnetocaloric Effect Research Articles

Inverse Magnetocaloric Effect in Heusler Ni44.4Mn36.2Sn14.9Cu4.5 Alloy at Low Temperatures

Direct measurements of the magnetocaloric effect were performed in a Heusler Ni44.4Mn36.2Sn14.9Cu4.5 alloy at cryogenic temperatures in magnetic fields up to 10 T. The maximum value of the inverse magnetocaloric effect in a 10 T field was ∆Tad = –2.7 K in the vicinity of the first-order magnetostructural phase transition at T0 = 117 K. Ab initio and Monte Carlo calculations were performed to discuss the effect of Cu doping into a Ni-Mn-Sn compound on the ground-state structural and magnetic properties. It is shown that with increasing Cu content the martensitic transition temperature decreases and the Curie temperature of austenite slightly increases. In general, the calculated transition temperatures and magnetization values correlated well with the experimental ones.

Inverse magnetocaloric effect and negative magnetoresistance in Ni50Mn30-xFexSn20-ySby (1 ≤ x ≤ 4 and 2 ≤ y ≤ 8) alloys

Inverse magnetocaloric effect and negative magnetoresistance in Ni50Mn30-xFexSn20-ySby (1 ≤ x ≤ 4 and 2 ≤ y ≤ 8) alloys

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.

Investigation of magnetocaloric effect in Holmium substituted Dysprosium iron garnet for magnetic refrigeration applications

The Dy1-xHox3Fe5O12(Ho-DyIG) with x=0.0 to 1.0 garnet samples are prepared by solid-state reaction route by sintering them at 1200 °C for 24 hours followed by calcination. The samples have simple cubic structure with Ia3¯d space group. The lattice constant is obtained from the Rietveld refinement technique and is found to be decreased from 12.4181Å to 12.3858Å with Ho doping. All the samples exhibit ferrimagnetic behavior below their transition temperature of 555K(x=0.0) to 545Kx=1.0. This drop in transition temperature is attributed to the dilution of Fea-O-Fed networks. All the samples show magnetic compensation because of the strong anisotropy induced at lower temperatures. In addition, we have also observed spin reorientation in all the samples of Ho-DyIG series. We have performed magnetocaloric measurements for x=0.4 and 0.8 samples and observed that the magnetic entropy is improved from 3.92 to 4.30J/kgK when measured at a maximum applied field of 5T around their respective Belov tranistion temperature i.e. TB. We have seen both normal and inverse magnetocaloric effects in these samples. To test the extent of magnetic refrigeration capacity, we have calculated the Relative Cooling Power, which comes out to be 364.6J/kg for x=0.4 and 313.0J/kg for x=0.8 samples at 5T magnetic field. The Arrott plots are also investigated and they have positive slope suggesting the presence of second-order phase transition in our samples.

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.

Tuning of the magneto-caloric effects in Ni43Mn46In11 magnetic shape memory alloys by substitution of boron

In this study, we report the structural, magnetic, and magnetocaloric properties of B substitution on the Mn site in Ni43Mn46−x B x In11(x = 0.5, 1.0) Heusler alloys. Crystal structure analysis using room-temperature x-ray diffraction data reveals both samples have mixed phases composed of cubic and tetragonal phases. The structural and magnetic phase transition characteristic temperatures are determined using differential scanning calorimetry, isothermal magnetization (MT), and isofield magnetization (MH) measurements. Both alloys exhibit inverse and direct magnetocaloric effects in the vicinity of their magnetostructural transition and Curie temperature (T C), respectively. For Ni43Mn45.0B1.0In11 a maximum magnetic entropy change of 25.06 J kg−1 K−1 is observed at 250 K for a magnetic field change of 5 T.

Giant irreversibility of the inverse magnetocaloric effect in the Ni47Mn40Sn12.5Cu0.5 Heusler alloy

Direct studies of the adiabatic temperature change (ΔTad) in the Ni47Mn40Sn12.5Cu0.5 Heusler alloy in steady magnetic fields up to 8 T by the extraction method and in pulsed magnetic fields up to 50 T were carried out in this paper. The alloy Ni47Mn40Sn12.5Cu0.5 demonstrates a magnetostructural phase transition (MSPT) of the first order in the 254–283 K temperature range as well as a second order phase transition near the Curie temperature TC = 313 K. An inverse magnetocaloric effect (MCE) was found in the region of the MSPT, and it reaches the maximum value ΔTad = −12 K in 20 T at the initial temperature T0 = 275 K. The irreversible part of the MCE reached ΔTir = −10 K when the field is completely removed. We consider the dynamics of the MCE in the vicinity of the MSPT and discuss the mechanisms that cause the giant irreversibility of the MCE as well as the possibilities of its application in hybrid cooling systems.

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.

Magnetic-field-induced transitions and the inverse magnetocaloric effect at liquid helium temperatures in the Mn1-xCoxNiGe system (0.15 ≤ x < 0.80)

Magnetic field-induced phase transitions found in the Mn1-xCoxNiGe system (0.15 ≤ x < 0.8) at T = 5 K may differ in nature and magnitude of the saturation magnetization of the initial weakly magnetic phase. These differences also affect the phenomena accompanying the transitions, specifically, the inverse magnetocaloric effect (MCE). In the current work, the mechanisms of these phenomena are analyzed within the framework of the magnetostructural model, which takes into account the difference in the limiting values of the magnetic order parameters in competing orthorhombic and hexagonal crystal structures. As follows from the analysis performed, the features observed in Mn1-xCoxNiGe can be explained by the realization at low temperatures of a metastable orthorhombic crystal state in magnetically ordered phases with a stable high-temperature hexagonal crystal structure.

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.

Determination of normal and inverse magnetocaloric effect in iron oxide thin films

Determination of normal and inverse magnetocaloric effect in iron oxide thin films

Low-temperature magnetic and magnetocaloric properties of orthorhombic DyNiSn

In this work, magnetic and magnetocaloric properties of antiferromagnetic (AFM) DyNiSn compounds which shows complex magnetic behavior at low-temperatures are investigated. Performed magnetic and specific heat measurements showed that except transition to the antiferromagnetic state at TN = 7.7(1) K, there are two more changes in the magnetic structure at T1 = 5.6(1) K = and T2 = 2.6(1) K. The magnetocaloric properties of the DyNiSn were determined indirectly from magnetic and specific heat measurements. DyNiSn shows normal and inverse magnetocaloric effect peaks at ∼9 K and ∼5 K, respectively. The maximum values of the magnetic entropy change (ΔSm), relative cooling power (RCP), and temperature averaged entropy change (TEC(5)) evaluated from magnetic measurements and for magnetic field change of 5 T are −8.0(1) Jkg−1K−1, 130(9) Jkg−1, and 8.7(1) Jkg−1K−1, respectively.

Magnetocaloric Effect in Half-Doped and Self-Doped Manganites: A Study to Green Refrigeration

Magnetic refrigeration has emerged as a promising and environmentally friendly technology due to its high efficiency and eco-friendly nature. It is becoming a strong competitor to traditional gas refrigeration and is often referred to as a green refrigeration technique. This technique utilizes the magnetocaloric effect (MCE) or inverse magnetocaloric effect (IMCE) to achieve a change in temperature after adiabatic demagnetization. Among various magnetocaloric materials, perovskite manganites have drawn significant attention due to their abundance and low field MCE. In this paper, a comparative study of MCE has been presented for two different types of manganites. The self-doped La0.9MnO3 shows a considerable amount of MCE (2.5 J/Kg-K) at an applied magnetic field of 10 kOe around 255 K. In contrast, Pr0.5Sr0.5Mn0.98Cr0.02O3another manganite, shows a comparably lower value of MCE (0.55 J/Kg-K) around 220 K under the same magnetic field, but it exhibits a large IMCE (1.26 J/Kg-K) around 150 K. This comparative study provides insights into the magnetocaloric properties of these manganites, which could have potential applications in green refrigeration.

Coexistence of normal and inverse magnetocaloric effect in inhomogeneous Ni95Cr5 layers

Understanding of the coexistence of normal and inverse magnetocaloric effects (MCE) makes it promising for use in magnetic cooling applications. This study discusses the selection of Ni95Cr5 layers and their expected magnetocaloric effects for an extended temperature range (200–800 K). These layers offer a wide range of suitable magnetic ordering temperatures as a function of thicknesses. A modified phenomenological model was used to estimate the entropy changes () and relative cooling power (RCP). Under adiabatic magnetic field variation, normal and inverse MCE are computed near the ferromagnetic-paramagnetic transition temperatures, T C and spin−glass transition temperatures, T G , respectively. Based on their values (= −0.06 to 0.11 J kg−1-K−1) and RCP( = 7.6 to 15.5 J kg−1) at the smallest magnetic field of 0.5 kOe, which are comparable to other MCE layer materials. We provide evidence of a strong correlation between the change in magnetic anisotropy (measured in terms of MR/MS and HC) below T G , which subsequently leads to the reversal of However, after annealing these effects somewhat vanish. The current study demonstrates that adjusting thickness, in addition to Cr doping, can externally regulate soft magnetic and magnetocaloric properties to create diverse magnetic ground states for future MCE and inverse MCE functionalities.

Magnetocaloric effect in the Jx−Jy Blume–Capel model

The magnetocaloric properties of the Jx−Jy Blume–Capel model with Jx/Jy=−0.5 are studied using the two point approximation of the Cluster Variation Method. The phase diagrams exhibit different phases depending on the anisotropy parameter, magnetic field, temperature and exchange interaction ratio. It is shown how the nature of the phase transition changes as parameters are varied. For an anisotropy parameter value of D=1.45, a tricritical point and a reentrant behavior are identified. It was found inverse and direct magnetocaloric effect. The inverse magnetocaloric effect of the model is enhanced at low fields and temperatures around jumps between plateaus of magnetization.

Magnetocaloric effect and magnetic phase diagram of EuRhAl4Si2

We report magnetocaloric effect (MCE) landscape and rich magnetic phase diagram of the quaternary compound EuRhAl4Si2 for magnetic field applied along the long axis (H || [001]) of the tetragonal unit cell. The MCE turns out to be a non-monotonic function of magnetic fields and temperatures containing regions of normal as well as inverse MCE. Our high-resolution magnetization data reveal the appearance of first order minor magnetization jumps with emergent phase separation below 5.5 K, within the magnetization plateau state. The magnetic phase diagram of EuRhAl4Si2 provides a fertile ground for statistical models.

Direct and inverse magnetocaloric effects in the antiferromagnetic rare earth (RE) rich RE6Ni2.25Al0.75 (RE = Dy, Ho and Er) compounds

The magnetic refrigeration (MR) by utilizing the magnetocaloric effect (MCE) of magnetic solids has been considered a promising, environmentally benign, energy-efficient cooling technology. However, the lack of promising magnetic substances has slowed the development of its active application. To identify suitable candidate materials, we herein identified the structural and magnetic properties together with the MCE and magnetocaloric performances of rare earth (RE) rich RE6Ni2.25Al0.75 (RE = Dy, Ho and Er) compounds. All the RE6Ni2.25Al0.75 compounds are confirmed to crystallized in orthogonal Ho6Co2Ga-type structure and underwent paramagnetic to antiferromagnetic magnetic transitions. Moreover, large direct (conventional) and inverse MCEs have been observed in all the RE6Ni2.25Al0.75 compounds. The values of peak magnetic entropy changes, temperature-averaged magnetic entropy changes with 5 K-lift and relative cooling powers under magnetic field change of 0–7 T are evaluated to be − 4.44 J/kg-K, − 4.38 J/kg-K and 230.6 J/kg for Dy6Ni2.25Al0.75, to be − 12.68 J/kg-K, − 12.26 J/kg-K and 378.2 J/kg for Ho6Ni2.25Al0.75, and to be − 17.52 J/kg-K, − 17.33 J/kg-K and 465.7 J/kg for Er6Ni2.25Al0.75, respectively.

Evolution of the inverse magnetocaloric effect for random-field to spin-glass crossover in SmCaCoMnO6−SmMnO3 nanocomposite

We observe an enhancement of inverse magnetocaloric effect (MCE) in $\mathrm{Sm}\mathrm{Ca}\mathrm{Co}\mathrm{Mn}{\mathrm{O}}_{6}$ (94%) and $\mathrm{Sm}\mathrm{Mn}{\mathrm{O}}_{3}$ (6%) nanocomposite due to uniform external field-induced random field (RF) to spin glass (SG) crossover. RF is generally observed in diluted antiferromagnet and dilute dipole-coupled Ising ferromagnet systems. Under the application of magnetic-field ($H$), such systems may show a crossover from RF to SG at low temperatures ($T$). Here, we report a similar type of crossover but in ferrimagnetic $\mathrm{Sm}\mathrm{Ca}\mathrm{Co}\mathrm{Mn}{\mathrm{O}}_{6}$ and antiferromagnetic $\mathrm{Sm}\mathrm{Mn}{\mathrm{O}}_{3}$ nanocomposite. A model of site dilution of the ferrimagnetic phase by the embedded antiferromagnetic regions is proposed. In this composite system, the RF appears at $T&lt;35$ K, which shows a crossover to SG at $T&lt;15$ K under the applied field. The enhanced inverse MCE (with an entropy change, $\ensuremath{-}\mathrm{\ensuremath{\Delta}}{S}_{M}\ensuremath{\sim}\ensuremath{-}0.95$ J ${\mathrm{Kg}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ for a change in $H\ensuremath{\sim}70$ kOe at $T\ensuremath{\sim}7.5$ K) due to the SG state is the consequence of field-induced RF-SG crossover giving highly $H$-dependent $\ensuremath{-}\mathrm{\ensuremath{\Delta}}{S}_{M}$ in the SG regime, a requisite for large MCE.