Room Temperature Magnetic Refrigeration Research Articles

Simulation study of heat transfer enhancement for all-solid-state room temperature magnetic refrigeration system

To address issues relating to large thermal resistance and low heat transfer efficiency between and inside magnetocaloric materials (MCM) in all-solid-state room-temperature magnetic refrigeration technology, this study adopted the method of inserting high thermal conductivity materials (HTCM) into MCM and coupling Peltier elements between MCMs to enhance the heat transfer inside MCM and between microcells, thereby improving the refrigeration performance of the system. In doing so, a two-dimensional simulation model was developed using COMSOL Multiphysics software. The cooling performance enhancement effect of the system resulting from heat transfer improvement within MCM and between MCMs was investigated separately. Furthermore, the impacts of various system operating parameters (such as the number of micro-cell divisions, initial operating temperature, heat transfer time, magnetic field strength, Peltier input voltage), different HTCMs and insertion volume ratios on the system’s cooling performance were explored. The simulation results reveal that, in comparison with the original magnetic refrigeration system, the optimized heat transfer time of the system following enhanced heat transfer within the MCM is reduced from 180s to 8s, accompanied by a 115% increase in the maximum temperature span. Furthermore, coupling the Peltier elements elevates the maximum temperature span by 274%.

Investigating the reversible nature of the magnetocaloric effect under cyclic conditions of the Ni50Mn34In15Ga1 magnetic shape memory alloy

This study explores the reversibility of the martensitic transformation (MT) and magnetocaloric (MC) response of the Ga-doped Ni50Mn35In15 magnetic shape memory alloys (MSMAs) with a Heusler structure. The direct and reverse MT occurs between temperatures TM ≈ 257 K and TA ≈ 266 K, respectively. The large MC effects resulting from the magnetic-field-induced first-order MT render these materials promising for room-temperature magnetic refrigeration. On account of both a low thermal hysteresis of MT (ΔThyst = 4 K) at a magnetic field of 2 T and a highly reproducible peak value of the adiabatic temperature change at MT (|∆Tad| ≈ 1.3 K for µ0H = 1.9 T), Ni50Mn34In15Ga1 MSMA emerges as a benchmark material for studying a cyclic stability of MC effects. During the first magnetic switching cycle, a reduction of ∆Tad at MT by approximately 1.3 is observed, significantly lower than the reported one for other MC materials undergoing similar first-order phase transitions. Subsequent cycles revealed a consistent stability of the magnetic-field-induced ∆Tad even after more than 200 magnetic field switching cycles. These findings suggest a notable degree of reversibility of the MT in the studied MSMA, which was also confirmed in the present work by a Temperature-First Order Reverse Curve distribution analysis.

Magnetocaloric effect and applied refrigeration performance of La(Fe,Si)13-based compounds

As a solid-state refrigeration technology, room-temperature magnetic refrigeration has several significant advantages comparing with conventional gas compression refrigeration, such as environmental friendliness, high energy efficiency and dependable operation. In the present study, the magnetocaloric effect and applied refrigeration performance of La0.8Ce0.2Fe11.6-xMn0.15+xSi1.25Al0.1H1.8 (x = 0, 0.03, 0.06, 0.09, 0.12) compounds were studied systematically. All alloys crystallize mainly in NaZn13-type phase with trace α-Fe phase between 1.36 and 1.80 wt%. The necessary heat treatment improves the formation of main phase. As x increases, the Curie temperature (Tc) decreases gradually from 295.3 K to 273.0 K. All alloys undergo strong field-induced first-order itinerant-electron metamagnetic transition. Under 0–1.5 T, the maximum magnetic entropy changes (-ΔSM)max for La0.8Ce0.2Fe11.6-xMn0.15+xSi1.25Al0.1H1.8 (x = 0, 0.03, 0.06, 0.09, 0.12) compounds vary from 10.9 J/(kg K) to 13.5 J/(kg K). And the maximum adiabatic temperature changes (ΔTad)max vary from 2.7 K to 3.9 K. To study the applied refrigeration performance, a rotary magnetic refrigerator is designed successfully, whose refrigeration temperature and cooling power meet the requirement of cold storage. Successful large-quantity preparation, giant magnetocaloric effect and excellent refrigeration performance suggest that, La0.8Ce0.2Fe11.6-xMn0.15+xSi1.25Al0.1H1.8 (x = 0, 0.03, 0.06, 0.09, 0.12) compounds can be used as the promising candidates for magnetic refrigerants.

Effect of Al doping on magnetocaloric effect and mechanical properties of La(FeSi)13-based alloys

La(Fe,Si)13 is a candidate room temperature magnetic refrigeration material owing to its large magnetocaloric effect and an adjustable Curie temperature. The structure, magnetocaloric effect, and mechanical properties of La(Fe,Si)13 strongly depend on its microscopic atomic environment. Proportional doping of magnetic or ductile elements can improve its magnetocaloric and mechanical properties. Here, magnetocaloric effect, and mechanical properties of Al-doped La(Fe,Si)13 alloys were studied through density functional theory calculations and experiments. The experimental results show that the doping of Al can increase the Curie temperature of the alloy, broaden the full width at half maximum (FWHM) and improve the mechanical properties of the alloy. The density functional theory describes the magnetic transition and mechanical behavior of the alloy, which is consistent with the experimental results. Therefore, the appropriate doping of Al in La(FeSi)13 alloy can obtain good integrated refrigeration capacity, which is helpful to realize multi-stage refrigeration application in a wide temperature range.

Development and experimental analysis of a multi-bed active magnetic regenerator

Room temperature magnetic refrigeration technology is a potentially efficient and environmentally friendly refrigeration technology. A magnetic refrigeration prototype with two high/low magnetic field regions was designed and built. The device consists of eight beds, using gadolinium particles as the magnetocaloric material, with a total filling mass of 1.35 kg. The hydraulic system consists mainly of a magnetic centrifugal pump, solenoid valves, and check valves. The flow of the heat transfer fluid through the regenerators is controlled by controlling the opening and closing of the solenoid valves. The no-load temperature span, cooling capacity, power consumption, and COP of the regenerators were investigated separately. The maximum no-load temperature span of 17.5 K was obtained at an AMR frequency of 0.5 Hz and flow rate of 1.15 L/min. The total power consumption and the magnetic power and pumping power were analyzed for different operating conditions.

Additive manufacturing for 3D microchannel structure using La(FexSi1-x)13 magnetic refrigerant via laser powder bed fusion

The fabrication of a three-dimensional (3D) channel/pillar structure with a submillimeter scale using La(FexSi1-x)13 magnetocaloric material was attempted via a laser powder bed fusion (LPBF) process to realize a regenerative bed for a room temperature magnetic refrigerator. The LPBF condition was found to govern not only the shaping conditions but also the metallographic structure in the as-fused state. The latter determines the quality of La(FexSi1-x)13 in the final state after annealing to homogenize the as-fused state, which has a strong impact on the magnetocaloric effect (MCE). The LPBF condition was optimized to balance the shaping and MCE performances from data science technique (i. e., the principal component analyses) by parameterizing the properties of the test specimens fabricated under varying conditions. The optimized LPBF condition enables fabrication of a 3D channel/pillar bed with magnetic entropy change of −17 J/kg K at 1 T. In the active magnetic regenerator-type module, the channel/pillar bed exhibited a lower performance than the target value because the channels were clogged by the adhesion of powders to pillars due to sintering occurring below the melt pool. Ideal correction of the experimental data indicated that unclogging the channel would revive the performance superior to that of the randomly packed bed while maintaining a lower pressure drop.

Research on microstructure evolution and surface quality of WEDM for magnetic refrigerant rare-earth gadolinium

Rare-earth gadolinium (Gd) is preferable for manufacturing regenerators of the core components of room-temperature magnetic refrigeration owing to its unique magnetocaloric and mechanical properties. However, the surface quality of the regenerator plays a crucial role in the heat transfer effect and service life of magnetocaloric systems during wire electrical discharge machining (WEDM) when fabricating rare-earth Gd array microstructure regenerators. In this study, different process parameters were used to conduct a process experiment of the WEDM of rare-earth Gd. First, the evolution of the surface microstructure and its causes were analyzed using a single-factor experiment, while a corrosion test was conducted on the samples. The analysis showed that the pulse-on time and open voltage considerably affected the surface quality of the processed samples, while the samples with better surfaces exhibited good corrosion resistance. Additionally, a Taguchi experiment was designed, and a regression analysis used to establish regression models between the process parameters (pulse-on time, pulse-off time, peak current, open voltage, and water pressure) and both surface roughness (SR) and material removal rate (MRR). The results showed that the average prediction errors of SR and MRR were only 5.34% and 5.48%, respectively.

Exploring phase formation and magnetic transitions in Sm(Fe1−xMnx)14B by Mössbauer spectroscopy

The Sm2(Fe1−xMnx)14B (0 ≤ x ≤ 0.3) rare earth alloy was prepared by a reduction-diffusion method, and a corresponding reduction-diffusion model was established. The crystal structure, microscopic morphology, and magnetic properties were systematically characterized to investigate the effect of Mn doping. The results show that the diffusion of Sm into FeB proceeded with the formation of the Sm2Fe14B phase from the very beginning of the reaction. Sm2(Fe1−xMnx)14B alloy undergoes a transition from the ferromagnetic phase (x = 0) to the paramagnetic phase (x = 0.2), and the average magnetic moment of Fe decreases from 2.066 to 0.719 µB as observed by 57Fe Mössbauer spectroscopy. In addition, the Curie temperature decreases rapidly from 620 to 230 K. In other words, a wide temperature-regulation of TC can be achieved by adjusting the Mn content, which is attributed to the fact that Mn doping greatly weakens the atomic exchange interactions. These results provide value for potential applications of Re–Fe-based alloys in room temperature magnetic refrigeration.

Experimental study of compact room temperature magnetic cooling system based on different flow time ratios

Magnetic refrigeration has become a promising new technology to replace conventional vapor-compression refrigeration technology, for it has excellent application characteristics such as the high efficiency, environmental friendliness and structural simplicity. Many studies have been carried out to analyze the various subsystems, but the interaction laws between the systems are not yet clear, and the optimization of each subsystem is still an area of research worth exploring. This work is based on a compact room temperature magnetic refrigeration system developed before, and carries out experimental research on the different flow time ratio to explore the correlation among refrigeration temperature span, cooling capacity, pressure drop, coefficient of performance (COP) and blow fraction under a fixed magnetic field timing. Especially, the effects of different flow time ratios (100%, 80%, 60%) on the system performance are studied under magnetic field timing of 1∶4∶1∶4 and a frequency of 0.45 Hz. The experimental results reveal that a low utilization factor combined with a high flow time ratio can achieve a greater temperature spread, whereas a high utilization factor combined with a high flow time ratio can accomplish a bigger cooling capacity. When the utilization factor is 0.42 and the flow time ratio is 100%, the maximum unloaded cooling temperature span is 26.2 K. Meanwhile, the effects of the utilization factor and flow time ratio on the pressure drop and COP of the regenerator are studied in detail. It is discovered that raising the flow time ratio and reducing the utilization factor both result in a fall in fluid velocity, which leads the pressure to further decrease and the COP to rise. In a word, this research investigates the relationship among cooling temperature span, cooling capacity, pressure drop, COP, and flow time ratio in a fixed magnetic field timing, thus providing the groundwork for future improving the performances of room temperature magnetic refrigeration systems.

Complete thermodynamic characterization of second-order phase transition magnetocaloric materials exclusively through magnetometry

To fully assess and improve the performance of near room-temperature magnetic refrigerants, it is crucial to measure and compare their three most relevant thermodynamic properties, and their dependence on temperature (T) and applied magnetic field (H): the isothermal entropy change, ∆Siso(T,H); the adiabatic temperature change, ∆Tad(T,H); and the heat capacity, Cp(T,H). Typically, each thermodynamic property requires its own specialized measurements, which are very time-demanding and can be challenging to setup. In this work, we report a complete thermomagnetic characterization of a benchmark magnetocaloric material, gadolinium, using a single and commercially available SQUID magnetometer. By improving a recently reported method with incremental field ramping steps for measuring temperature through magnetization, we obtained a ∆Tad(T) curve under a 1 T field change with its peak amplitude and maximizing temperature respectively within 2 % and 0.8 % of previously reported values for gadolinium. We were also able to estimate the temperature dependent heat capacity, Cp(T,μ0H=0.85T), using the ∆Tad(T) measurements from magnetometry combined with magnetization versus temperature curves at different field values. This estimate of Cp around the transition temperature of gadolinium is within a relative error of 11 % of the experimental and reported values. The reported methodology allows the complete characterization of a second-order magnetocaloric material (∆Siso(T,H), ∆Tad(T,H), Cp(T,H)) around its Curie temperature using a single and widely available device, which can accelerate studies of different magnetocaloric materials’ performance, and approximate their implementation in magnetic refrigeration and/or waste heat energy harvesting industries.

Near-room-temperature magnetocaloric properties at 1.5 T coupled with relaxor dielectric properties in La2CoMnO6 nanoparticles

Achieving high magnetic entropy change at low magnetic fields near room temperature may pave the way to attaining room temperature magnetic refrigeration. We report herein on high magnetic entropy change at 1.5 T around 291 K in La2CoMnO6 manganite nanoparticles. The magnetic, magnetocaloric, and dielectric properties of La2CoMnO6 nanoparticles of sizes D = 30–40 nm are reported. Powder X-ray diffraction analysis and Raman spectra have confirmed the co-existence of a monoclinic ordered phase and a partially disordered phase. Magnetization measurements have showna long-range ferromagnetic to paramagnetic transition at a Curie temperature of 291.9 K. A maximum magnetocaloric entropy change of 0.88 J kg−1 K−1 has been achieved upon application of a 1.5 T external magnetic field. Dielectric measurements have shown relaxation behavior and a high dielectric constant. The detailed electrical conduction mechanism is explained in terms of various polaron hopping mechanisms. The mutual origin of magnetocaloric and dielectric relaxor behavior in La2CoMnO6, along with its high dielectric constant, confirms that there is strong coupling between the magnetic and dielectric properties of this material, making it suitable for multifunctional applications.

Room-temperature magnetocaloric properties of (La1-xNdx)2Fe10.7Mn0.3Si2Hy

Magnetocaloric properties of (La1-xNdx)2Fe10.7Mn0.3Si2Hy (x = 0.1 and 0.2) are evaluated to develop a room-temperature magnetic refrigerant. While Nd which is introduced to reduce the thermal hysteresis has a negligible effect on magnetic properties, the partial replacement of Fe with Mn converted the first-order magnetic transition to a second-order and TC is reduced by 50 K to near room temperature. The peak entropy change, ΔSM|pk values are 10.4 J kg−1 K−1 (at 290 K) for x = 0.1 and 10.6 J kg−1 K−1 (at 286 K) for x = 0.2 with μ0∆H = 3 T. The maximum values of the adiabatic temperature change, ΔTad are 4.11 K (at 283 K) for x = 0.1 and 4.05 K (at 289 K) for x = 0.2 with μ0∆H = 1.4 T. Because TC can be shifted by the addition of Mn to room temperature, this series of compounds can be used as an efficient magnetic refrigerant or a combination as a composite refrigerant for an active magnetic refrigeration cycle.

LaFe13−xSixHz magnetocaloric composites obtained via room temperature processing

LaFe13−xSixHz alloys are promising candidates for room temperature magnetic refrigeration, but their brittle behaviour hinders their shaping into magnetocaloric devices. Metal bonding of LaFe13−xSixHz particles has been performed to overcome this issue, but the fabrication processes reported so far involve the exposure of LaFe13−xSixHz particles to temperatures where dehydrogenation occurs, which deteriorates their magnetocaloric properties. This work proposes two processing routes (P1 and P2) which were carried out entirely at room temperature, hence avoiding dehydrogenation. Route P1 consisted of binding LaFe13−xSixHz particles with Sn, while in route P2 two binders were combined: Sn and Cu. Final average porosities were equal to 12.8 % (P1) and 12.1 % (P2), which are comparable to what has been reported for hot processed composites, and differential scanning calorimetry analyses indicated that dehydrogenation did not occur during processing, an improvement in comparison to hot processing. Complementarily, the mechanical behaviour of the composites was investigated via Weibull analysis. Characteristic strengths of 49.9 MPa (P1) and 60.7 MPa (P2) were found under uniaxial compression, showing that the combination of Cu and Sn as binders promoted higher strength. Weibull moduli of 10.9 (P1) and 8.8 (P2) were identified, which are greater than what has been previously reported for a bulk alloy, indicating that embedding LaFe13−xSixHz particles in a metallic matrix led to a less brittle-like behaviour.

Improving the performance of room temperature magnetic regenerators using Al2O3-water nanofluid

The present study examines the use of Al2O3-water nanofluid as the heat transfer fluid in a magnetic regenerator and evaluates the improved cooling capabilities of the device. Room-temperature magnetic refrigeration exploits a special property of some materials, the “magnetocaloric effect”, that is the ability of the material to change its temperature when exposed to rapid changes in an external magnetic field. As adiabatic magnetic field variations of 1 to 1.5 T produce a small temperature change of a few degrees, active magnetic regeneration is often employed to achieve larger temperature spans for practical cooling applications. The effectiveness of this process greatly depends on the properties of the heat transfer fluid, which is usually a water-based mixture. High values of the fluid thermal conductivity enhance heat transfer allowing for higher cooling capacity. This work presents the outcome of a comprehensive simulation study evaluating the improved performance of a gadolinium-based regenerator using a water-based mixture with added Al2O3 nanoparticles as the heat transfer fluid. In this analysis, both the volume concentration of nanofluid and the particle size were varied. The combined effect of heat transfer enhancement and pressure drop increase was also investigated through the second law efficiency. On average, a more than 15 % increase in cooling capacity was observed when using Al2O3 (6 % vol, 20 nm particles), and the COP can be preserved or increased with a properly tuned regulation of the cycle time and the utilization factor of the regenerator.

On the origin of cracking in laser powder bed fusion processed LaCe(Fe,Mn,Si)13, and the impact of post-processing

LaCe(Fe,Mn,Si)13 magnetocaloric material printed by laser powder bed fusion (LPBF) has a huge potential for magnetic refrigeration. However, high crack and defect susceptibility in LPBF processing remains a limitation of its application. This study optimised the LPBF process parameters for optimally dense blocks. The volumetric energy density condition, EV = 250 J/mm3, showed the lowest crack density and porosity fraction. The behaviour and mechanism of different cracks and defects were revealed. The lower energy density parameter sets, caused by higher scanning speeds and hatch spacing, lead to the formation of lack-of-fusions. The hot cracking observed was attributed to stress concentration and a stable liquid film. The solid-state cracks observed were expected in the microstructure of the as-fabricated (AF) sample due to the poor toughness of the La/Ce/Si-rich phases. Thermal heat treatment and quenching increased the magnetocaloric effect (MCE) of the AF sample. The maximum magnetic entropy change (∆Smax) of the heat-treated sample was − 3.68 Jkg−1K−1 at 294 K, when applied to a 1 T field. The Curie temperature (Tc) (298 K when applied 0.01 T field) and superior MCE make the material an ideal choice for realising room-temperature magnetic refrigeration.

Combinatorial design of partial ordered Al–Cr–Mn–Co medium-entropy alloys for room temperature magnetic refrigeration applications

Multi-component alloys have received increasing interest for functional applications in recent years. Here, we explore the magnetocaloric response for Al–Cr–Mn–Co medium-entropy alloys by integrated theoretical and experimental methods. Under the guidance of thermodynamic and ab initio calculations, a dual-phase system with large magnetic moment, i.e., Al50Cr19Mn19Co12, is synthesized, and the structural and magnetocaloric properties are confirmed via characterization. The obtained results indicate that the selected alloy exhibits a co-continuous mixture of a disordered body-centered cubic and an ordered B2 phase. The ab initio and Monte Carlo calculations indicate that the presence of the ordered B2 phase is responsible for the substantial magnetocaloric effect. The magnetization measurements demonstrated that this alloy undergoes a second-order magnetic transition with the Curie temperature of ∼300 K. The magnetocaloric properties are examined using magnetic entropy change, refrigeration capacity, and adiabatic temperature change. The property-directed strategy explored here is intended to contribute to the study of potential multi-component alloys in magnetocaloric applications.

Galinstan liquid metal as the heat transfer fluid in magnetic refrigeration

Room-temperature magnetic refrigeration is a promising technology in which cooling is achieved by exploiting a special property of some materials, the “magnetocaloric effect” (MCE), i.e., the ability of the material to change its temperature when it undergoes changes in the applied external magnetic field. For magnetic field variations on the order of 1–1.5 T, the MCE results in small adiabatic temperature changes of a few degrees so, in most cases, the designs and prototypes presented by various research groups employ active magnetic regeneration to increase the temperature span required for practical cooling devices. The effectiveness of the regenerator, and thus of the refrigeration device, depends heavily on the properties of the heat transfer fluid, which is usually a water-based mixture. High values of the fluid thermal conductivity greatly affect the heat transfer between the MCE and the fluid allowing faster operation and higher cooling capacity. In this study, the use of a gallium based liquid metal, i.e., Galinstan, is investigated to quantify this improvement. Galinstan was found not to be aggressive to gadolinium at room temperature and it resulted not affected by magnetic induction. The authors report the results of an extensive simulation campaign to characterize the performance of an active magnetic regenerator made of 0.5 mm thick gadolinium sheets using Galinstan as a heat transfer fluid. The results are compared to those of the same device using water; friction is also accounted for since the high density of this liquid metal leads to a high demand for pumping power. On average, a more than tenfold increase in cooling capacity was observed when using Galinstan, but the COP was severely penalized by the higher frictional losses. To avoid this effect, the cycle time and the utilization factor must be adjusted, or the geometry changed by using thicker sheets and ducts for the same Gd weight. In this way a cooling increase of 400% is achieved with the same COP.

Synthesis, structure, morphology, magnetism, and magnetocaloric-effect studies of La0.7Sr0.3Mn1−xFexO3 perovskite nanoparticles

Single-phase La0.7Sr0.3Mn1−xFexO3 (x = 0.0, 0.04, 0.08, 0.12, 0.16, 0.20, 0.24, and 0.30) perovskites were synthesized by the sol-gel method followed by sintering at 800 °C for 5 h. The XRD showed the rhombohedral structure with the R-3c space group and there was a slight change in the lattice parameters as well as the unit cell volume of the compounds with Fe doping. The average particle size of the samples was in the range of 43–70 nm. All samples show a ferromagnetic to paramagnetic second-order magnetic phase transition at TC and TC decreases linearly from 370 K for x = 0 to 98 K for x = 0.3. From the XPS measurement, it was found that the oxidation state of Fe and La are + 3 and the Mn has a mixed valence state of Mn4+/Mn3+. The saturation magnetization and the blocking temperature were suppressed by the Fe substitution while (-ΔSM)max was found to decrease as Fe content increased. The sample with x = 0.08 has a Curie temperature of 297 K, the highest relative cooling power (RCP) of 153 J/kg, and (-ΔSM)max value of 1.46 J/kg.K at µoΔH = 2.8 T. The La0.7Sr0.3Mn1−xFexO3 iron-substituted manganites may be regarded as a prospective candidate for room-temperature magnetic refrigeration applications.

Improving work temperature span and reversibility of magnetoelastic transition of (Mn,Fe)2(P,Si) alloys by Mg doping

Magnetocaloric materials with wide working temperature span and reversible magnetic transition are beneficial for the magnetic refrigerator. Besides of giant magnetocaloric effect, (Mn,Fe)2(P,Si) alloys exhibit significant thermal/magnetic hysteresis and a narrow working temperature span. In this work, the impact of Mg doping on the phase structure and magnetocaloric effect of Mn1.05Fe0.9P0.5Si0.5-xMgx alloys has been studied. The results show that all samples crystallize into Fe2P-type main phase with little impurity phase. After Mg doping, the lattice parameter a of the main phase increases from 6.027(0) Å to 6.049(0) Å and c decreases from 3.488(6) Å to 3.480(6) Å, which leads to the increase of Curie temperature. Density functional theory calculation results confirm that the Mg atom located on the 2c site can increase the covalent bond length, and then enhance the ferromagnetic coupling between atoms leading to the increase of Curie temperature. Moreover, the first-order magnetic phase transition of Mn1.05Fe0.9P0.5Si0.5-xMgx alloys is inhibited with the increase of Mg content, which results in the decrease of thermal/magnetic hysteresis and the increase of the effective working temperature span. For Mn1.05Fe0.9P0.5Si0.48Mg0.02 alloy, it has a Curie temperature of about room temperature, effective refrigeration capacity of 291.7 J·kg−1, working temperature window of 46 K and magnetic entropy change of 9.4 J·kg−1·K−1. The alloy can be an excellent candidate in room temperature magnetic refrigeration devices with a wide temperature span.

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.