Significant Magnetocaloric Effect Research Articles

Doping position estimation for FeRh-based alloys

FeRh-based alloys have attracted significant attention due to their magnetic phase transition and significant magnetocaloric effects. These properties position them as promising candidates for fundamental research and practical applications, including magnetic cooling and targeted drug delivery. The study of FeRh alloys, particularly those where Rhodium or Iron atoms are substituted with other transition metals, is crucial as certain substitutions preserve the alloy’s magnetocaloric properties. However, even within a specific structural type and without considering competing phases, determining which atom (Fe or Rh) is replaced upon introducing a third element remains unclear. This paper addresses this ambiguity through ab initio calculations. We propose an approach to predict whether a dopant will replace Fe or Rh, offering insights into the electronic and structural factors influencing the substitution. Additionally, we present a dataset of ab initio calculations on doped FeRh alloys, which will support future data-driven modeling efforts. Our findings not only advance the understanding of FeRh-based alloys but also contribute to the design of novel materials for experimental and industrial applications.

Hourglass-Shaped Homo- and Heteronuclear Nonanuclear Lanthanide Clusters: Structures, Magnetism, Photoluminescence, and Theoretical Analysis.

Synthesis of nonameric cationic clusters [Dy9(acac)16(μ3-OH)8(μ4-OH)2]OH·6H2O (1), [Dy8Tb (acac)16(μ3-OH)8(μ4-OH)2]OH·2H2O (2), and [Gd9(acac)16(μ3-OH)8(μ4-OH)2]OH·6H2O (3) (acac = acetylacetonate) is reported. The emission spectrum of 1 shows Dy(III) ion characteristic bands assignable to the 4F9/2 → 6HJ (J = 15/2 to 9/2) transitions. Emission due to both Dy(III) and Tb(III) ions is observed for 2 in the visible range, with Tb(III) specific bands appearing due to the 5D4 → 7FJ (J = 6, 4, and 3) transitions. Cluster 3 exhibits a significant magnetocaloric effect (MCE), with -ΔSm values increasing with decrease in temperature and increase in field, reaching -ΔSmmax = 20.98 J kg-1 K-1 at 2 K and 9 T. Isotropic magnetic coupling constants (Js) in 3 derived from density functional theory (DFT) calculations reveal that the exchange interactions are antiferromagnetic and weak. Compound 3 possesses S = 7/2 ground state arising from the central Gd(III) ion along with several nested excited states due to competing antiferromagnetic interactions that yield reasonably large MCE values. Utilizing computed exchange coupling interactions, we have performed ab initio CASSCF/RASSI-SO/POL_ANISO calculations on antiferromagnetic 1 and 2 to estimate the exchange interactions using the Lines model. For 2, Dy(III)···Tb(III) exchange interactions were extracted for the first time and were found to be weakly antiferromagnetically coupled.

Large magnetocaloric effect and giant magnetoresistance in rare earth based intermetallic compound ErAl3: construction of magnetic phase diagram

This study explores the magnetic and magnetotransport behavior of polycrystalline ErAl3 compound. The polycrystalline compound adopts HoAl3-type structures with the R-3m space group, No. 166-2 and hR60 configurations. Multiple magnetic orderings and two field-induced metamagnetic transitions are observed. ErAl3 exhibits a significant magnetocaloric effect (MCE), −ΔSM = 15.25 J kg−1 K−1 and high relative cooling power of 383 J kg−1 with applied magnetic field change (ΔH) of 70 kOe near the paramagnetic to ferromagnetic transition, showcasing its potential for magnetic refrigeration technology. The compound also demonstrates metallic behavior, with a notable magnetoresistance of 48.5 % at 2 K due to the suppression of antiferromagnetism. The magnetic phase diagram reveals four distinct phases influenced by temperature and magnetic field, identified through the study of the MCE.

Three [Ln2Co2] cluster-based three-dimensional frameworks: Syntheses, structure, and magnetocaloric effect

The heterometallic 3d-4f clusters are being researched, for some time now, as being applicable to molecular magnetism. Especially, the Gd3+-containing multi-nuclear clusters attract wide study attention, on account of the significant magnetocaloric effect (MCE). Herein, three-dimensional (3D) 3d-4f heterometallic clusters are successfully gained via solvothermal conditions, formulated as {[Ln2Co2Na2(L)2(C2O4)2(H2O)4]·(H2O)2}n (abbreviated as Ln2Co2, Ln = Gd for 1; Ln = Tb for 2, and Ln = Dy for 3; L = ethylenediaminetetraacetic acid disodium salt). Structural analysis shows that Ln2Co2 clusters are mainly consistent of the [Ln2Co2Na2(L)2(C2O4)2(H2O)4] metal frames, which are the asymmetric building units. Interestingly, [Ln2Co2Na2(L)2(C2O4)2(H2O)4] metal frames can be constructed by one chain-shaped [Ln2(C2O4)2], one [Na2(H2O)2] dimer, and two [CoL(H2O)] units. Tree building units are connected to constitute 3D structure of Ln2Co2. In addition, the metal ions make Gd2Co2 exhibit the magnetic entropy change (-∆Sm = 31.17 J kg−1 K−1 at 2.0 K and 7.0 T) and ideal -∆Sm value at low-field condition (20.18 J kg−1 K−1 at 2.0 K and 2.0 T).

The large magnetocaloric effect in GdErHoCoM (M = Cr and Mn) high-entropy alloy ingots with orthorhombic structures

High-entropy alloys (HEAs) with significant magnetocaloric effects (MCEs) have attracted widespread attention due to their potential magnetic refrigeration applications over a much more comprehensive temperature range with large refrigerant capacity (RC). However, most of them are metallic glasses (MGs) with problems of limited size, resulting in the difficulty of further applications. Therefore, research on HEAs with crystalline structures and giant MCE is urgently needed. In this paper, GdErHoCoM (M = Cr and Mn) rare-earth HEA ingots with orthorhombic structures are developed, and their magnetic behavior and MCE are studied in detail. Phase investigations find that the main phase of GdErHoCoM ingots is probably (GdErHo)Co with an orthorhombic Ho3Co-type structure of a space group of Pnma. The secondary phases in GdErHoCoCr and GdErHoCoMn are body-center-cubic Cr and Mn-rich HoCo2-type phases, respectively. Magnetic investigations reveal that both ingots undergo a first-order magnetic phase transition below their respective Neel temperatures. Above their respective Neel temperatures, a second-order transition is observed. The Neel temperatures are 40 and 56 K for GdErHoCoCr and GdErHoCoMn, respectively. Additionally, the GdErHoCoCr and GdErHoCoMn ingots exhibit maximum magnetic entropy changes and RC values of 12.29 J/kg/K and 746 J/kg and 10.13 J/kg/K and 606 J/kg, respectively, under a magnetic field of 5 T. The ingots GdErHoCoM (M = Cr and Mn) show excellent MEC properties and can be manufactured easily, making them promising for magnetic refrigerant applications.

DFT and Monte Carlo investigations of electronic structure, magnetic, magnetocaloric, and thermoelectric properties of the perovskite SrXO3 (X = Mn and Fe) compound

The structural, electronic, magnetic, magnetocaloric, and thermoelectric properties of the SrXO3 (X = Mn and Fe) perovskite compounds were investigated using first-principles calculations. It was observed that the SrXO3 compounds are G-anti-ferromagnetic perovskites with partial magnetic moment with a value of 2.7 [Formula: see text] and 2.4 [Formula: see text] for Mn-3d and Fe-3d orbitals for SrMnO3 and SrFeO3, respectively. Moreover, by using Monte Carlo simulation (MCs) combined with the Metropolis algorithm, the calculated coupling interactions between the magnetic atoms Mn–Mn and Fe–Fe are [Formula: see text][Formula: see text]meV and [Formula: see text][Formula: see text]meV for SrMnO3, [Formula: see text][Formula: see text]meV and [Formula: see text][Formula: see text]meV for SrFeO3, respectively. Furthermore, a significant magnetocaloric effect (MCE) was observed around the Néel temperature of [Formula: see text][Formula: see text]K (for SrMnO3) and [Formula: see text][Formula: see text]K (for SrFeO3), and the maximal simulated magnetic entropy and relative cooling power values of all the studied compounds are found to be 100[Formula: see text]J/kg (for SrMnO3) and 110[Formula: see text]J/kg (for SrFeO3), respectively, with an applied magnetic field of [Formula: see text] T. These results are in complete agreement with the experimental results and more specifics than other theoretical calculations. Hence, SrXO3 compounds are considered promising candidates for magnetic refrigeration at low temperature.

Magnetism, magnetocaloric and magnetostrictive effects in RCo2 – type (R = Tb, Dy, Ho) laves phase compounds

This work presents the results of a comparative analysis of the thermal, magnetic, magnetocaloric and magnetostrictive properties of the Dy0.42Ho0.42Tb0.16Co2, Dy0.5Ho0.5Co2 and TbCo2 compounds. All studied compounds have the MgCu2-type Laves phase structure at room temperature. Dy0.5Ho0.5Co2 and TbCo2 demonstrate first- and second-order transitions from a paramagnetic state to a magnetically ordered one, respectively. Special attention is given to determining the order of magnetic phase transition in a multicomponent compound with three rare earth elements (Tb,Dy and Ho). Features of the magnetocaloric effect and magnetostriction of (Tb,Dy,Ho)Co2 compounds have been studied in magnetic fields up to 14 T and in wide temperature range (4.2 – 300 K). The joint manifestation of significant magnetocaloric and magnetovolume effects at the Curie temperature can be useful for a variety of technical applications.

Reversible single-crystal-to-single-crystal transition in Gd(III) metal-organic frameworks induced by heat and solvents with a significant magnetocaloric effect.

The design and synthesis of a Gd(III) metal-organic framework with the formula [Gd4(BTDI)3(DMF)4]n (JXUST-40, H4BTDI = 5,5'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diisophthalic acid) are reported hererin. Interestingly, a reversible single-crystal-to-single-crystal transition between JXUST-40 and {[Gd4(BTDI)3(H2O)4]·6H2O}n (JXUST-40a) was achieved under the stimulation of heat and solvents. Both JXUST-40 and JXUST-40a exhibited good stability when soaked in common solvents and aqueous solutions with pH values of 1-12. Magnetic studies showed that JXUST-40a has a larger magnetocaloric effect with -ΔSmaxm = 26.65 J kg-1 K-1 at 2 K and 7 T than JXUST-40 due to its larger magnetic density. Structural analyses indicated that the coordinated solvent molecules play a crucial role in the coordination environment around the Gd(III) ions and the change in the framework, ultimately leading to the changes in the pore size and magnetism between JXUST-40 and JXUST-40a. In addition, both isomorphic [Dy4(BTDI)3(DMF)4]n (JXUST-41) and {[Dy4(BTDI)3(H2O)4]·6H2O}n (JXUST-41a) displayed slow magnetic relaxation behaviour.

Crystal structure change in magnetocaloric compounds (Er,Nd)2Fe17

Numerous research studies have documented materials exhibiting a significant magnetocaloric effect (MCE) at elevated temperatures. However, there is a scarcity of materials displaying both intriguing MCE and a second-order transition phase from a ferromagnetic state to a paramagnetic state at approximately 300 K. In this current study, we provide an account of the structural, magnetic, and magnetocaloric characteristics of the (Er,Nd)2Fe17 system. (Er,Nd)2Fe17 compound was prepared by arc melting under high pure argon and homogenized at 1073K to minimize the amount of other possible impurity phases. X-ray diffraction (XRD) coupled with Rietveld analysis with FullProf computer code was used for the structural study. This compound crystallizes in the rhombohedral Th2Zn17 and Th2Ni17 type structure.the Er2−xNdxFe17 compounds adopt the hexagonal Th2Ni17-structure type and extends for x = 0, 0.4, 0.7, while for x = 1.75, 1.85 and 2 adopts the rhombohedral Th2Zn17-structure type. Hence, the temperature dependence of the magnetization is determined. The Curie temperature increases from 294K to 335K after the total Er substitution by Nd. The magnetic entropy changes ΔSM, and the relative cooling power and temperature-averaged entropy change (TEC) are reported. Based on these results, the compounds under investigation exhibit an intriguing magnetocaloric effect in the vicinity of room temperature.

Magnetic and magnetocaloric characteristics of the mixed Graphullerene-like structure: A theoretical study

This paper presents an investigation of the magnetic and magnetocaloric properties of a mixed Graphullerene-like nanostructure. The Blume–Capel model is employed, and Monte Carlo computations were performed using the Metropolis algorithm. The study examines various spin configurations within different parameter planes and reveals stable configurations. Furthermore, the paper analyzes magnetizations, susceptibilities, specific heat, and Binder cumulant as a function of the temperature to determine the transition temperature and characterize magnetic phase transitions in the system. The suitability of the investigated structure for magnetic refrigeration was also assessed by examining the magnetic entropy change and relative cooling power at different external magnetic field strengths. The results show a direct correlation between the external magnetic field and maximum entropy changes, indicating a significant magnetocaloric effect.

Bifunctional Lanthanide-Based Coordination Polymers: Conversion of CO2 and Highly Selective Luminescence Sensing for Acetylacetone.

A series of bifunctional Ln(III)-based coordination polymers (CPs) {Ln(L)(DMA)2(NO3)}n [Ln(III) = Eu (1), Gd (2), and Dy (3); organic ligand H2L = 2,2'-(1,3,5,7-tetrahydroxyoctahydro-4,8-ethanopyrrolo[3,4-f]isoindole-2,6(1H,3H)-diyl)diacetic acid)] have been successfully synthesized. CPs 1-3 are isostructural and constructed from the dimeric Ln2 unit in which two adjacent LnIII ions are bridged by two μ3-carboxyl oxygens, and the Ln2 dimeric unit is connected by two NO3- ions, four DMA molecules, and four completely protonated L2- ligands forming a 2D layer structure. The magnetic research reveals that CP 2 shows a significant cryogenic magnetocaloric effect (-ΔSm = 22.9 J kg-1 K-1; T = 2.0 K and ΔH = 7.0 T), whereas CP 3 exhibits slow magnetic relaxation property under Hdc = 0 Oe field. Additionally, the luminescence explorations revealed that CP 1 can act as a recyclable luminescent probe for pollutant acetylacetone among various small organic solvent molecules, and the corresponding detection limit is 10-7 mol/L. More importantly, CP 1 also exhibits good catalytic performance in the cycloaddition reaction of CO2 and epoxides or cyanamides under mild conditions. As far as we know, CP 1 represents the first bifunctional lanthanide homogeneous catalyst that can efficiently catalyze the reaction of cyanamides/epoxides with CO2 simultaneously.

Giant magnetocaloric effects of MnNiSi-based high-entropy alloys near room temperature

The materials combining high-entropy alloys with good mechanical properties and magnetic materials with a significant magnetocaloric effect are among the best candidates for magnetic refrigeration. For this purpose, the high-entropy alloys (MnNiSi)1-x(FeCoGe)x (x = 0.4, 0.42, 0.45, and 0.47) were designed in this study. The effects of the Si/Ge ratio on the magnetocaloric effect and mechanical properties were also investigated. The results show that high-entropy alloy (MnNi)0.6Si0.62(FeCo)0.4Ge0.38 possesses a Vickers hardness value of 580.6HV2 and compressive strength of 267 MPa with respect to a significant entropy change of 48.5 J·kg−1K−1 under a magnetic field of 5 T near the Curie temperature of 308.8 K. In order to clearly understand the origin of this excellent comprehensive performance, the influence mechanism of crystal structure and configurational entropy were explored. Furthermore, the first-principles calculations indicated that the magnetic properties mainly originate from Mn atoms located in 3d sites and are influenced by the interaction between the Mn and Fe atoms. Additionally, the total magnetic moment and electron density are taken into account to reveal their influence on magnetocaloric properties.

Effect of Ni alloying on the microstructure and magnetocaloric properties of Gd-based metallic microfibers

Gd-based metallic microfibers have been the research highlights due to the significant magnetocaloric effect. Herein, the atomic cluster micro-regions are constructed in Gd-based microfibers to further improve the magnetocaloric effect. The results show that the continuous and amorphous microfibers with excellent softly magnetic and thermal stability properties are obtained. The maximum magnetic entropy change -ΔSmmax of Gd-based microfibers increases first and then decreases with Ni alloying degree increase. Among which, the better magnetocaloric properties is obtained in (Gd60A20lCo20)95Ni5 microfibers. The maximum magnetic entropy change, refrigeration capacity (RC), and relative cooling power (RCP) at 5 T reach 11.57 J/kg K, 834.14 J/kg, and 1138.16 J/kg, respectively. The outstanding magnetocaloric properties of microfibers are attributed to the indirect interaction coupling caused by Ni elements and the atomic cluster micro-regions, which lead to a fundamental shift in magnetic entropy. The findings of this study promote the application of Gd-based microfibers in the field of magnetic refrigeration.

Anisotropic Metamagnetic Spin Reorientation and Rotational Magnetocaloric Effect of Single Crystal NdAlGe.

Magnetic anisotropy strongly influences the performance of the magnetocaloric effect. We investigated the magnetocaloric properties of the NdAlGe single crystal with I41md structure. The temperature-dependent magnetization revealed significant anisotropic properties; stable antiferromagnetic transition at TN = 6 K for H//a and meta-magnetic spin reorientation at low temperature (T ≤ 5 K) within an intermediate field (H = 2 T) for H//c. During the metamagnetic spin reorientation, the abrupt change of the magnetic entropy leads to a significant magnetocaloric effect with negative magnetic entropy change (∆SM) by -13.80 J kg-1 K-1 at TC = 5.5 K for H = 5 T along the H//c axis. In addition, the antiferromagnetic state for H//a shows the inverse magnetocaloric effect(I-MCE) by positive entropy change ∆SM = 2.64 J kg-1 K-1 at TN = 6 K for H = 5 T. This giant MCE accompanied by the metamagnetic transition resulted in a significantly large relative cooling power (158 J/kg at H = 5 T) for H//c. The giant MCE and I-MCE can be applied to the rotational magnetocaloric effect (R-MCE) depending on the crystal orientations. NdAlGe exhibits rotational entropy change ∆Sc-a = -12.85 J kg-1 K at Tpeak = 7.5 K, H = 5 T. With comparison to conventional MCE materials, NdAlGe is suggested as promising candidate of R-MCE, which is a novel type of magnetic refrigeration system.

Tunable structures and magnetic / optical properties of six Cd(II)-based coordination polymers by introducing different para- or dia-magnetic metal ions

One monometallic and five heterometallic coordination polymers (HCPs) based on homophthalic acid (H2HPA), [Cd2(HPA)2(H2O)2]·H2O (1), [CdMn(HPA)2(H2O)2]·H2O (2), [Cd3Co(HPA)4(H2O)4]·2H2O (3), [CdCo(HPA)2(DMSO)(H2O)2] (4), [CdNa2(HPA)2(μ2-H2O)(H2O)] (5) and [Cd2Na2(HPA)3(μ2-H2O)(H2O)2] (6), were synthesized solvothermally. Complexes 1-3 have similar two-dimensional (2D) layer structures except that all or part six-coordinated Cd(II) ions in 1 were replaced by the six-coordinated Mn(II) or Co (II) ion in 2 and 3, respectively. Complex 4 shows an 1D ladderlike structure, and 5 and 6 exhibit different 2D layer structures. The different structures of 3/4 and 5/6 could be assembled directly by controlling the different pH values with other same reaction conditions, respectively. Magnetic studies reveal that the introducing of para-magnetic Mn(II) and Co(II) ions endow antiferromagnetic interarions between the neigboring spins in 2–4, and 2 with isotropic Mn(II) ion displays a significant cryogenic magnetocaloric effect with a maximum −ΔSm value of 19.29 J K−1 kg−1 at 2 K and ΔH = 7 T. In addition, the solid-state photophysical properties of 1, 5 and 6 display blue emissions centered at ca. 453 nm, 448 nm and 428 nm, respectively.

The Stepwise Formation of {Gd4} Clusters with Magnetocaloric Effect, Accompanied by In Situ Condensation Cyclization Reactions

Accompanied by condensation cyclization reactions in solvothermal conditions, three Gd(III) tetranuclear clusters {[Gd4(Lx)2(μ3-OH)2(NO3)2(Ac)6]} (x = 1, 2, and 3 for 1, 2, and 3, respectively) were isolated and characterized, wherein, L1–3 were in situ synthesized from bis[3-(pyridin-2-yl)-1H-1,2,4-triazole-5-yl]methane (bptm), 5-bptm (bis[3-(5-methylpyridin-2-yl)-1H-1,2,4-triazole-5-yl]methane), and 4-bptm (bis[3-(4-methylpyridin-2-yl)-1H-1,2,4-triazole-5-yl]methane) in the presence of GdIII ions, respectively. The step-by-step formation process (bptm → L1 → Gd1(L1)1 → Gd2(L1)1 → Gd2(L1)2 → Gd3(L1)2 → Gd4(L1)2) of the tetranuclear clusters in 1 was tracked by mass spectrometry technology. The study of their magnetic properties showed that 1–3 displayed significant magnetocaloric effects with the −ΔSm values of 29.25–29.64 J K–1 kg–1.

Effect of the post annealing cooling rate on the martensitic transformation and the magnetocaloric effect in Ni-Mn-Sn ribbons

We report the modification of the martensitic transformation in Ni-Mn-Sn ribbons by controlling the post annealing cooling rate. Isothermal holding above the order-disorder temperature for 24 h ensured homogeneous grain growth and uniform microstructural features in all the samples. However the atomic order was tailored by varying the cooling rate. The furnace-cooled sample exhibited the highest austenite stabilization and the lowest martensitic transformation temperature of 200.2 K, whereas the air-cooled sample exhibited the highest transformation temperature of 298.5 K. The martensite evolved as ferromagnetic clusters in an anti-ferromagnetic matrix in the samples with high atomic disorder, whereas long-range anti-ferromagnetic co-relations developed in the highly ordered samples. The martensitic transformation in the as-spun ribbons generated a significant magnetocaloric effect and a large entropy change of 4.02 J/kg/K, for a ΔH of 2 T. Furthermore, furnace cooling increased the relative cooling power of the ribbons by 23.3 J/kg over the as-spun specimens.

Study on the critical behavior and magnetocaloric effect of RCrO3 (R = Gd, Dy)

In this study, we aim to examine the critical behavior and magnetocaloric effect of RCrO3 (R = Gd, Dy) polycrystal synthesized by solid-state sintering. As per the heat capacity fitting curves, GdCrO3 and DyCrO3 fit the 3D-XY and 3D-Ising models, respectively. The analysis of heat capacity curves, field cooling (FC), and zero-field cooling (ZFC) curves reveals two magnetic phase transitions in the samples, with TNCr = 174 K, TNGd = 3.7 K and TNCr = 152 K, TNDy = 3.5 K for GdCrO3 and DyCrO3, respectively. Under a 50 kOe magnetic field, the maximum magnetic entropy change (−ΔSmmax) and relative cooling efficiency (RCP) of the sample are 39.9 J/kg K, 373.4 J/kg and 15.9 J/kg K, 276 J/kg for the two samples, respectively. We believe that the significant magnetocaloric effect of GdCrO3 is associated with its critical behavior. This provides an additional reference for the origin of the large magnetocaloric effect of materials.

Alloying and magnetic disordering effects on the thermodynamic properties and phase stability of Co2Cr(Ga, Si) and Co2Cr(Al, Si) Heusler alloys

Using the first-principles exact muffin-tin orbital method in combination with the coherent potential approximation, the alloying and magnetic disordering effects on the thermodynamic properties and phase stability of the ferromagnetic L21- and D022-CoxCr78−xZ11Si11 (Z=Ga and Al, 46≤x≤62) alloys are systematically investigated. It is shown that at 0 K, with increasing x the D022 structure gets relatively more and more stable in the energy and stabilized instead in the two groups of alloys with x≥56 and 60, respectively. There, upon the martensitic transformation (MT) the bulk modulus gets a little larger than that of the austenite, and both significant magnetocaloric and magnetovolume effects could be also expected. The tetragonal shear elastic constant (C′=(C11−C12)/2) of the L21 phase decreases whereas that (Cs=C11+C12+2C33−4C13) of the D022 phase increases with the Co addition, mechanically favoring the relative stability of the more ductile D022 martensite as well. The magnetic excitations decrease the electronic total energy but increase the phonon vibrational free energy of the D022 phase relative to the L21 one. The two effects nevertheless almost offset each other at their Curie temperature. The reentrant MT (RMT) is then predicted without the magnetic excitations effect in the Z=Ga and Al alloys with 50≤x≤54 and 54≤x≤58, respectively, and their critical temperatures (TM) for the RMT decrease with increasing x, in line with the measured data of the Z=Ga alloys. With the Co addition, the increase of the relative stability of their D022 phase is finally confirmed maybe originating from the increase of the Co 3d minority DOS around the Fermi level in their L21 phase.

Structural, Magnetic, and Magnetocaloric Studies of Ball-Milled Fe100−xTx (T = Ni and Mn) Alloy

Iron-transition metal-based binary and ternary alloys have attracted great attention due to their relevant mechanical, electrical, and magnetic properties. In this paper, we systematically investigate the structural, magnetic, and magnetocaloric behavior of as-milled Fe65T35 (T = Ni and Mn) alloy. The polycrystalline alloys were produced by the planetary ball milling, using a powder-to-ball ratio of 1:3. A structural study reveals that both Fe65Ni35 and Fe65Mn35 compounds have stabilized in α and γ mixed phase within the cubic crystal structure. The alloyed compounds are further characterized by high-resolution field emission scanning electron microscopy (HR-FESEM), which confirms the mixing of both metals in the alloying process. Temperature-dependent magnetic studies do not show any blocking in zero-field-cooled and field-cooled results; however, the field-dependent magnetization study demonstrates the ferromagnetic nature with small hysteresis in both compounds. Both compounds show a significant magnetocaloric effect over a wide temperature range around room temperature. Fe65Ni35 exhibit a slightly higher value in comparison to Fe65Mn35. In both the alloys, magnetic entropy change follows the power law behavior against the external magnetic field, and the value of exponent ‘m’ explains the presence of magnetic correlation. Our investigation in this study communicates that the phase control or coexistence of both phases may be efficacious in obtaining the desirable characteristic of magnetic and magnetocaloric demeanors in such a binary Fe-T alloy.