The caloric effect in Gd5Si2Ge2 compound is studied experimentally and theoretically. The first-order phase transition is sensitive to both magnetic field and pressure. It indicates that the influences of magnetic field and pressure on the phase transition are virtually equivalent. Moreover, the theoretical analyses reveal that the total entropy change is almost definite at a certain Curie temperature whether the applied external field is magnetic field or pressure. On the basis of theoretical analyses, the entropy change simultaneously induced by magnetic field and hydrostatic pressure can be obtained experimentally. As for Gd5Si2Ge2 compound, the entropy change curve is broadened dramatically, and the refrigerant capacity is improved from 284.7 to 447.0 J/kg. Additionally, the required magnetic field in magnetic refrigeration technique may be reduced by the application of hydrostatic pressure.
We report on calorimetry under applied hydrostatic pressure and magnetic field at the antiferromagnetic (AFM)-ferromagnetic (FM) transition of Fe$_{49}$Rh$_{51}$. Results demonstrate the existence of a giant barocaloric effect in this alloy, a new functional property that adds to the magnetocaloric and elastocaloric effects previously reported for this alloy. All caloric effects originate from the AFM/FM transition which encompasses changes in volume, magnetization and entropy. The strong sensitivity of the transition temperatures to both hydrostatic pressure and magnetic field confers to this…
There is currently great interest in replacing the harmful volatile hydrofluorocarbon fluids used in refrigeration and air-conditioning with solid materials that display magnetocaloric, electrocaloric or mechanocaloric effects. However, the field-driven thermal changes in all of these caloric materials fall short with respect to their fluid counterparts. Here we show that plastic crystals of neopentylglycol (CH3)2C(CH2OH)2 display unprecedentedly large pressure-driven thermal changes near room temperature due to molecular reconfiguration, and that these changes are comparable with those exploi…
Solid-state cooling using barocaloric materials is a promising avenue for eco-friendly, inexpensive and highly efficient cooling. To design barocaloric compounds ready for deployment, it is essential to understand their thermodynamic behaviour under working conditions. To this end, we have studied the rotational dynamics in the molecular-ionic crystal ammonium sulfate under pressure, providing detailed insight into the origin of its large barocaloric effect. Using quasielastic neutron scattering experiments, we show that rotation of the ammonium cations is facilitated by pressure in the low-en…
By combination of two independent approaches, nuclear resonant inelastic X-ray scattering and first-principles calculations in the framework of density functional theory, we determine the element-resolved vibrational density of states in the ferromagnetic low temperature and paramagnetic high temperature phase of LaFe$_{13-x}$Si$_x$. This allows us to derive the lattice and electronic contribution to the entropy change at the first-order phase transformation, which are both of considerable magnitude. The change in lattice entropy is dominated by magneto-elastic softening, which originates from…
Here we report magneto-thermal properties of Gd3Ir compounds using magnetic and heat capacity data. We observed large isothermal entropy change, adiabatic temperature change and relative cooling power are 4.1J/Kg, 4K and 437J/Kg on 50KOe respectively.
Structural, magnetic and magnetocaloric properties of Mn2-xCrxSb compounds have been studied. In these compounds a first order magnetic phase transition from the ferrimagnetic to the antiferromagnetic state occurs with decreasing temperature, giving rise to giant inverse magnetocaloric effects that can be tuned over a wide temperature interval through changes in substitution concentration. Entropy changes as high as 7.5 J/kgK have been observed, and a composition independent entropy change is obtained for several different concentrations/working temperatures, making these compounds suitable ca…
We report on the existence of acoustic emission during the paramagnetic-monoclinic to ferromagnetic-orthorhombic magnetostructural phase transition in the giant magnetocaloric Gd5Si2Ge2 compound. The transition kinetics have been analyzed from the detected acoustic signals. It is shown that this transition proceeds by avalanches between metastable states.
As one of magnetic refrigerants with giant magnetocaloric effect (GMCE), MnFePGe-based compounds had drawn tremendous attention due to their many advantages for practical applications. In this paper, correlations among preparation conditions, magnetic and crystal structures, and magnetocaloric effects (MCE) of the MnFePGe-based compounds are reviewed. Structure evolution and phase transformation in the compounds as a function of temperature, pressure, and magnetic field were reported. Influences of preparation conditions to the chemical composition and microstructure homogeneity of the compoun…
The tetragonal layered compounds TbTiGe and ErTiGe order antiferromagnetically at 276 K and 39 K, respectively. Partial substitution of Mo for Ti in these two compounds modifies the magnetic interactions giving rise to a ferromagnetic ground state which results in an enhanced magnetocaloric effect. The magnetic entropy change in ErTi0.85Mo0.15Ge for a magnetic field change of 5 T is ~10.5 J/kg/K against ~0.8 J/kg/K for ErTiGe in the vicinity of the magnetic transition. Thus, magnetocaloric properties of such layered materials may be tunable by suitable chemical substitutions.
We report the magnetic, magnetocaloric and magnetoresistance results obtained in Tb(Ni1-xFex)2 compounds with x=0, 0.025 and 0.05. Fe substitution leads to an increase in the ordering temperature from 36 K for x=0 to 124 K for x=0.05. Contrary to a single sharp MCE peak seen in TbNi2, the MCE peaks of the Fe substituted compounds are quite broad. We attribute the anomalous MCE behavior to the randomization of the Tb moments brought about by the Fe substitution. Magnetic and magnetoresistance results seem to corroborate this proposition. The present study also shows that the anomalous magnetoca…
We report the anomalous magnetocaloric behavior in the polycrystalline compound Tb2Ni2Sn. The magnetization measurements show that this compound shows multiple magnetic transitions, which are attributed to the coexistence of ferromagnetic and antiferromagnetic phases at low temperatures. With increase in field and temperature, the compound undergoes a metamagnetic transition to a ferromagnetic state. In the temperature range where the antiferromagnetic phase is dominant, it exhibits inverse (negative) magnetocaloric effect. At temperatures close to the Neel temperature, the compound shows posi…
Due to critical environmental issues there is a pressing need to switch from current refrigeration methods based on compression of greenhouse gases to novel solid-state cooling technologies. Solid-state cooling capitalizes on the thermal response of materials to external fields named "caloric effect". The barocaloric (BC) effect driven by hydrostatic pressure is particularly promising from a technological point of view since typically presents larger cooling potential than other caloric variants (e.g., magnetocaloric and electrocaloric effects driven by magnetic and electric fields, respective…
Heat capacity of polycrystalline R2Ti3Ge4 (R = Gd, Tb and Er) compounds (Orthorhombic, Sm5Ge4-type, Space group Pnma) has been studied in the temperature range of 1.8 K to 300 K in various applied magnetic fields. The compounds with magnetic lanthanide elements show interesting low field magnetism intrigued by possible presence of competing antiferromagnetic and ferromagnetic interactions. The magnetocaloric effect in these compounds is estimated from the field dependent heat capacity data. The magnetic entropy change and the adiabatic temperature change in the vicinity of the magnetic transit…
Magnetic and magnetocaloric properties of polycrystalline samples of Gd1-xSmxMn2Ge2 have been studied. All the compounds except GdMn2Ge2 show re-entrant ferromagnetic behavior. Multiple magnetic transitions observed in these compounds are explained on the basis of the temperature dependences of the exchange strengths of the rare earth and Mn sublattices. Magnetocaloric effect is found to be positive at the re-entrant ferromagnetic transition, whereas it is negative at the antiferro-ferromagnetic transition. In SmMn2Ge2, the magnetic entropy change associated with the re-entrant transition is f…
The effect of Ge substitution on the magnetization, heat capacity, magnetocaloric effect and magnetoresistance of GdMn2Si2-xGex (x=0, 1, and 2) compounds has been studied. The magnetic transition associated with the Gd ordering is found to change from second order to first order on Ge substitution. Magnetic contributions to the total heat capacity and the entropy have been estimated. Magnetocaloric effect has been calculated in terms of adiabatic temperature change (deltaTad) as well as isothermal magnetic entropy change (deltaSM) using the heat capacity data. The temperature dependence of the…
The effect of external pressure on the magnetic properties and magnetocaloric effect of R(Co1-xSix)2 [R= Er, Dy and x=0, 0.025 and 0.05] compounds has been studied. The ordering temperatures of both the parent as well as the Si substituted compounds are found to decrease with pressure. In all the compounds, the critical field for metamagnetic transition increases with pressure. It is seen that the magnetocaloric effect in the parent compounds is almost insensitive to pressure, while there is considerable enhancement in the case of Si substituted compounds. Spin fluctuations arising due to the …
Using Density Functional Theory and a thermodynamic model [Physical Review B 86, 134418 (2012)], in this paper, we provide an approach to systematically screen compounds of a given Heusler family to predict ones that can yield giant magnetocaloric effect driven by a first-order magneto-structural transition. We apply this approach to two Heusler series Ni$_{2-x}$Fe$_{x}$Mn$_{1+z-y}$Cu$_{y}$Sb$_{1-z}$ and Ni$_{2-x}$Co$_{x}$Mn$_{1+z-y}$Cu$_{y}$Sb$_{1-z}$, obtained by cosubstitution at Ni and Mn sites. We predict four new compounds with potentials to achieve the target properties. Our computation…
Processing magnetocaloric materials into magnetic refrigerant particles is an essential issue in developing high-performance magnetic refrigerators. Here, we succeed in stably producing magnetocaloric particles of the promising material HoAl2 by a newly devised method based on electrode induction melting gas atomization process. The particle size range is on the order of submillimeter, which is suitable for practical refrigeration systems. The resulting particles with less contamination have good morphological, magnetic, and magnetocaloric properties: (i) almost spherical shapes with few inter…
The crystal and magnetic structures of AlFe2B2 have been studied with a combination of X-ray and neutron diffraction and electronic structure calculations. The magnetic and magnetocaloric properties have been investigated by magnetisation measurements. The samples have been produced using high temperature synthesis and subsequent heat treatments. The compound crystallises in the orthorhombic crystal system Cmmm and it orders ferromagnetically at 285 K through a second order phase transition. At temperatures below the magnetic transition the magnetic moments align along the crystallographic $a$…
We predict the existence of large barocaloric effects above room temperature in the thermoelectric fast-ion conductor Cu$_{2}$Se by using classical molecular dynamics simulations and first-principles computational methods. A hydrostatic pressure of $1$ GPa induces large isothermal entropy changes of $|ΔS| \sim 15$-$45$ Jkg$^{-1}$K$^{-1}$ and adiabatic temperature shifts of $|ΔT| \sim 10$ K in the temperature interval $400 \le T \le 700$ K. Structural phase transitions are absent in the analysed thermodynamic range. The causes of such large barocaloric effects are significant $P$-induced variat…
The crystal and magnetic structure of the magnetocaloric compound FeMnP0.5Si0.5 have been studied by means of neutron and X-ray powder diffraction. Single phase samples of nominal composition FeMnP0.5Si0.5 have been prepared by the drop synthesis method. The compound crystallizes in the Fe2P-type structure (P-62m) with the magnetic moments aligned along the aaxis. It is found that the Fe atoms are mainly situated in the tetrahedral 3g site while the Mn atoms prefer the pyramidal 3f position. The material is ferromagnetic (TC = 382 K) and at 296 K the total magnetic moment is 4.4 μB/f.u. It is …
By virtue of the itinerant electron metamagnetism (IEM), the RCo2 compounds with R=Er, Ho and Dy are found to show first order magnetic transition at their ordering temperatures. The inherent instability of Co sublattice magnetism is responsible for the occurrence of IEM, which leads to interesting magnetic and related properties. The systematic studies of the variations in the magnetic and magnetocaloric properties of the RCo2-based compounds show that the magnetovolume effect plays a decisive role in determining the nature of magnetic transitions and hence the magnetocaloric effect (MCE) in …
Large thermal hysteresis in the MnFe(P, Si, B) system hinders the heat exchange rate and thus limits the magnetocaloric applications at high frequencies. Substitution of Mn by V in Mn1-xVxFe0.95P0.593Si0.33B0.077 and Mn1-xVxFe0.95P0.563Si0.36B0.077 alloys was found to reduce the thermal hysteresis due to a decrease in the latent heat. Introducing V increases both the field-induced transition temperature shift and the magnetic moment per formula unit. Thus, a decease in the thermal hysteresis is obtained without losing the giant magnetocaloric effect. In consequence, an ultralow hysteresis (0.7…
We report the magnetocaloric effect in terms of isothermal magnetic entropy change as well as adiabatic temperature change, calculated using the heat capacity data. Using the zero field heat capacity data, the magnetic contribution to the heat capacity has been estimated. The variations in the magnetocaloric behavior have been explained on the basis of the magnetic structure of these compounds. The refrigerant capacities have also been calculated for these compounds.
We report a systematic investigation of the magnetic and magnetocaloric properties of Dy5Pd2 and Dy5PdNi. Our study on these compounds gave evidence that they exhibit complex magnetic behaviour along with the presence of glass-like magnetic phase. Furthermore, in these compounds both second order and first order phase transitions were present, which were validated through Arrott plots and Landau parameter analysis. AC susceptibility along with time dependent magnetisation study has confirmed the presence of double cluster glass-like freezing in both Dy5Pd2 and Dy5PdNi. These compounds show sig…
We report the structural, magnetic properties, and magnetocaloric effect of a new polycrystalline compound of $\mathrm{Tb_2Rh_3Ge}$. This present compound crystallizes with $\mathrm{Mg_2Ni_3Si}$-type of rhombohedral Laves phases (space group $R\overline{3}m$, hR18). The magnetic properties and magnetocaloric effect of the $\mathrm{Tb_2Rh_3Ge}$ is explored through dc-magnetization measurements. Temperature dependence of magnetization revealed that the compound exhibits ferromagnetic behavior with $T_C$$=$56 K. The field dependence of magnetization indicates that $\mathrm{Tb_2Rh_3Ge}$ is a soft …
The ternary intermetallic RTX compounds (R = rare earth, T = transitional metal, X = p-block metal) have been investigated extensively in the past few decades due to their interesting physical properties. Recently, much attention has been paid to the magnetocaloric effect (MCE) of these RTX compounds, especially the ones with heavy rare-earth, for their potential application in low temperature magnetic refrigeration. In this paper, we review the MCE of RTSi and RTAl systems with R = Gd~Tm, T = Fe~Cu and Pd, which are widely investigated in recent years. It is found that these RTX compounds exh…
The phase transformation kinetics of LaFe$_{11.41}$Mn$_{0.30}$Si$_{1.29}$-H$_{1.65}$ magnetocaloric compound is addressed by low rate calorimetry experiments. Scans at 1 mK/s show that its first order phase transitions are made by multiple heat fllux avalanches. Getting very close to the critical point, the step-like discontinuous behavior associated with avalanches is smoothed out and thermal hysteresis disappears. This result is confirmed by magneto-resistivity measurements and allows to measure accurate values of the zero field hysteresis ($ΔT_{hyst}$ = 0.37 K) and of the critical field (H$…
The processing of promising magnetocaloric materials into spheres is one of the important issues on developing high-performance magnetic refrigeration systems. In the present study, we achieved in producing spherical particles of a giant magnetocaloric compound HoB2 by a crucible-free gas atomization process, despite its high melting point of 2350 C. The particle size distribution ranges from 100 to 710 micrometers centered at 212-355 micrometers with the highest yield of 14-20wt% of total melted electrode, which is suitable for magnetic refrigeration systems. The majority of the resulting par…
In this article, our recent progresses about the effects of atomic substitution, magnetic field and temperature on the magnetic and magnetocaloric properties of the LaFe13-xAlx compounds are reviewed. With the increase of aluminum content, the compounds exhibit successively an antiferromagnetic (AFM), a ferromagnetic (FM), and a mictomagnetic state. Furthermore, the AFM coupling of LaFe13-xAlx can be converted to a FM coupling by substituting Si for Al, Co for Fe and magnetic rare-earth R for La, or introducing interstitial C or H atom. However, low doping levels lead to FM clusters embedded i…
In this paper we explore the magnetocaloric effect (MCE) of chromium-doped elpasolite Cs$_2$NaAl$_{1-x}$Cr$_x$F$_6$ (x = 0.01 and 0.62) single crystals. Our magnetization and heat capacity data show the magnetocaloric potentials to be comparable to those of garnets, perovskites and other fluorides, producing magnetic entropy changes of 0.5 J/kg$\cdot$K (x = 0.01) and 11 J/kg$\cdot$K (x = 0.62), and corresponding adiabatic temperature changes of 4 K and 8 K, respectively. These values are for a magnetic field change of 5 T at a temperature around 3 K. A clear Schottky anomaly below 10 K, which …
Inelastic neutron scattering measurements were performed on single crystals of the antiferromagnetic compound Mn5Si3 in order to investigate the relation between the spin dynamics and the magneto-thermodynamic properties. It is shown that among the two stable antiferromagnetic phases of this compound, the high temperature one has an unusual magnetic excitation spectrum where propagative spin-waves and diffuse spin-fluctuations coexist. Moreover, it is evidenced that the inverse magnetocaloric effect of Mn5Si3, the cooling by adiabatic magnetization, is associated with field induced spin-fluctu…
A strong electronic reconstruction resulting in a quenching of the Fe magnetic moments has recently been predicted to be at the origin of the giant magnetocaloric effect displayed by Fe2Pbased materials. To verify this scenario, X-ray Magnetic Circular Dichroism experiments have been carried out at the L edges of Mn and Fe for two typical compositions of the (Mn,Fe)2(P,Si,B) system. The dichroic absorption spectra of Mn and Fe have been measured element specific in the vicinity of the first-order ferromagnetic transition. The experimental spectra are compared with first-principle calculations …
Magnetic, thermal, magnetocaloric and transport properties of polycrystalline HoRuSi have been studied. It was found that the compound shows magnetic transitions at T1=18 K and T2=8 K. Magnetization data reveal that the ferromagnetic ordering is dominant in this compound. Magnetocaloric effect has been estimated from M-H-T data and the -ΔSM has been found to be 12.8 J/kg K for field of 50 kOe, which is comparable to some potential refrigerant materials in same temperature regime.
We present a study of the magnetoresistance, the specific heat and the magnetocaloric effect of equiatomic $RET$Mg intermetallics with $RE = {\rm La}$, Eu, Gd, Yb and $T = {\rm Ag}$, Au and of GdAuIn. Depending on the composition these compounds are paramagnetic ($RE = {\rm La}$, Yb) or they order either ferro- or antiferromagnetically with transition temperatures ranging from about 13 to 81 K. All of them are metallic, but the resistivity varies over 3 orders of magnitude. The magnetic order causes a strong decrease of the resistivity and around the ordering temperature we find pronounced mag…
Magnetocaloric effect in Mn4FeGe3-xSix compounds has been studied by dc magnetization measurements. For the parent compound Mn4FeGe3, the paramagnetic to ferromagnetic transition temperature TC is above room temperature (320 K), which initially remains constant for small Si substitution at the Ge site and then decreases marginally with an increase in Si concentration. A large change in magnetic entropy at the TC, under a magnetic field variation of 50 kOe, with typical values of 5.9, 6.5, 5.9 and 4.4 J kg-1 K-1 for x = 0, 0.2, 0.6, and 1 samples, respectively, along with a broad operating temp…
Caloric responses (temperature changes) can be induced in solid-state materials by applying external stimuli such as stress, pressure, and electric and magnetic fields. The magnetic-field-stimulated response is called the magnetocaloric effect, and materials that exhibit this property have long been sought for applications in room temperature magnetic cooling due to their potentially superior efficiency and low impact on the environment. Other solid-state caloric phenomena are less developed, but are likewise under intense investigation. Here we introduce a new material that not only displays …
The compounds FeMnAsxP1-x are very promising as far as commercial applications of the magnetocaloric effect are concerned. However, the theoretical literature on magnetocaloric materials still adopts simple molecular-field models in the description of important properties like the entropy variation that accompanies applied isothermal magnetic field cycling, for instance. We apply a Green function theoretical treatment for such analysis. The advantages of such approach are well-known since the details of the crystal structure are incorporated in the model, as well as a precise description of co…
Perovskite manganite La0.5Ca0.5-x xMnO3 (LCMO) nanomaterials were elaborated using the sucrose modified auto combustion method. Rietveld refinements of the X-ray diffraction patterns of the crystalline structure confirm a single-phase orthorhombic state with Pbnm space group (No. 62). The Ca-vacancies were voluntarily created in the LCMO structure in order to study their influence on the magnetic behaviour in the system. The magnetic susceptibility was found to be highly enhanced in the sample with Ca-vacancies. Paramagnetic-to-ferromagnetic phase transition was evidenced in both samples aroun…
In this paper, we report on the magnetocaloric properties of some selected multiferroic oxides, namely HoMn2O5 and La2(Ni,Co)MnO6 compounds which exhibit transition points from 10K up to almost room temperature. In order to avoid grain boundary effects and structural inhomogeneity observed frequently in polycrystalline samples, only single crystals were considered for this study.
Magnetic and heat capacity measurements have been carried out on the polycrystalline sample of DyNi which crystallizes in the orthorhombic FeB structure (space group Pnma). This compound is ferromagnetic with a Curie temperature of 59 K. Magnetization-field isotherms at low temperatures shows a step-like behavior characteristic of metamagnetic transitions. The magnetocaloric effect has been measured both in terms of isothermal magnetic entropy change and adiabatic temperature change for various applied magnetic fields. The maximum values of the entropy change and the temperature change are fou…
The compounds, PrCo9Si4 and NdCo9Si4, have been recently reported to exhibit first-order ferromagnetic transitions near 24 K. We have subjected this compound for further characterization by magnetization, heat-capacity and electrical resistivity measurements at low temperatures in the presence of magnetic fields, particularly to probe magnetocaloric effect and magnetoresistance. The compounds are found to exhibit rather modest magnetocaloric effect at low temperatures peaking at Curie temperature, tracking the behavior of magnetoresistance. The magnetic transition does not appear to be first o…
Magnetic and magnetocaloric properties of high-purity, giant magnetocaloric polycrystalline and single-crystalline Fe2P are investigated. Fe2P displays a moderate magnetic entropy change which spans over 70 K and the presence of strong magnetization anisotropy proves this system is not fully itinerant but displays a mix of itinerant and localized magnetism. The properties of pure Fe2P are compared to those of giant magnetocaloric (Fe,Mn)2(P,A) compounds helping understand the exceptional characteristics shown by the latter which are so promising for heat pump and energy conversion applications…
The magnetocaloric effect (MCE) in many rare earth (RE) based intermetallic compounds has been extensively investigated during last two decades, not only due to their potential applications for magnetic refrigeration but also for better understanding of the fundamental problems of the materials. This paper reviews our recent progress of magnetic properties and MCE in some binary or ternary intermetallic compounds of RE with low boiling point metal(s) (Zn, Mg, and Cd). Some of them are exhibiting promising MCE properties which make them also attractive for low temperature magnetic refrigeration…
A binary intermetallic compound Er5Pd2 has been investigated using dc and ac magnetic susceptibilities, magnetic memory effect, isothermal magnetization, non-linear dc susceptibility, heat capacity and magnetocaloric effect studies. Interestingly, even though the compound does not show geometrical frustration it undergoes glassy magnetic phase transition below 17.2 K. Investigation of dc magnetisation and heat capacity data divulged absence of long-ranged magnetic ordering. Through magnetic memory effect, time dependent magnetization and ac susceptibility studies it was revealed that the compo…
We explored the Fe rich side of the (Mn,Fe)2(P,Ge) magnetocaloric system. The transition temperature of this system is extremely easy to tune with careful manipulation of Fe and Ge content as well as stoichiometrical proportions, which gives rise to the real possibility of lowering the price of this compound and thus make it economically viable for practical magnetocaloric applications. Novel and unexpected magnetic properties observed in this system suggest an exciting potential for permanent magnet application in a limited concentration range.
We compute the magnetocaloric effect (MCE) in the GdTX (T=Sc, Ti, Co, Fe; X=Si, Ge) compounds as a function of the temperature and the external magnetic field. To this end we use a density functional theory approach to calculate the exchange-coupling interactions between Gd$^{3+}$ ions on each compound. We consider a simplified magnetic Hamiltonian and analyze the dependence of the exchange couplings on the transition metal T, the p-block element X, and the crystal structure (CeFeSi-type or CeScSi-type). The most significant effects are observed for the replacements Ti $\to$ Sc or Fe $\to$ Co …
We report the effect of partial substitution of Dy-site by rare-earths (R=Gd, Er and La)on the magnetic and magnetocaloric behavior of a mixed metal oxide DyFe0.5Cr0.5O3.Structural studies reveal that substitution of Dy by R has a minimal influence on the crystal structure. Magnetic and heat capacity studies show that the magnetic transition around 121 K observed for DyFe0.5Cr0.5O3 remains unchanged with rare-earth substitution, whereas the lower magnetic transition temperature is suppressed/enhanced by magnetic/non-magnetic substitution. In all these compounds, the second order nature of magn…
Structural, magnetic and magnetocaloric properties of Fe2P-based Mn-Fe-P-Si compounds were investigated. The study reveals a large magneto-elastic coupling that starts to develop in the paramagnetic state and grows when the ferromagnetic transition temperature is approached. Based on the behavior of the magneto-elastic coupling, we show the thermal evolution of the magnetic moments. On cooling, magnetic moments on the tetrahedral site form and gradually increase in the paramagnetic state. At the magnetic ordering temperature the moments attain a much larger value in a discontinuous step. We al…
The resistivity, magnetoresistance and in-field heat capacity measurements were performed on GdPt$_{2}$ intermetallic compound. The magnetocaloric parameters $ΔT_{ad}$ and $-ΔS$ were derived from the in-field heat capacity data. Comparison has been made between the magnetocaloric effect $-ΔS$ and difference in resistivity $-Δρ$ $(=ρ(H)-ρ(0))$ as a function of temperature. There is distinct difference in the temperature dependence of $-ΔS$ and $-Δρ$ below the ferromagnetic transition temperature. However after removing the domain wall contribution from $-Δρ$, the nature of $-ΔS$ and $-Δρ$ depen…
The nature of the magnetic transition, critical scaling of magnetization, and magnetocaloric effect in Mn$_{1+x}$Fe$_{4-x}$Si$_{3}$ ($ x =$ 0 to 1) are studied in detail. Our measurements show no thermal hysteresis across the magnetic transition for the parent compound which is in contrast with the previous report and corroborate the second order nature of the transition. The magnetic transition could be tuned continuously with Mn substitution at the Fe site. The Mn substitution leads to a linear increase in the unit cell volume and a slight reduction in the effective moment. A detailed critic…
Ni-Mn-based metamagnetic shape-memory alloys exhibit a giant thermal response to magnetic fields and uniaxial stress which can be utilized in single caloric or multicaloric cooling concepts for energy-efficient and sustainable refrigeration. However, during cyclic operation these alloys suffer from structural and functional fatigue as a result of their high intrinsic brittleness. Here, we present based on Fe-doping of Ni-Mn-In a microstructure design strategy which simultaneously improves cyclic stability and maintains the excellent magnetocaloric and elastocaloric properties. Our results reve…
Recently the inverse magnetocaloric effect is observed for different compounds. However there is very rare for any manifestation of the effect to be seen in manganites. We have found inverse magnetocaloric effect in the case of polycrystalline La$_{0.125}$Ca$_{0.875}$MnO$_{3}$. Such phenomenon is attributed to the stabilization of antiferromagnetic state associated with inherent magnetic inhomogeneous phases for this compound.
We report complex magnetic, magnetoresistance (MR) and magnetocaloric properties of Gd4RhAl and Tb4RhAl forming in the Gd4RhIn type cubic structure. Though the synthesis of the compounds was reported long ago, to our knowledge, no attempt was made to investigate the properties of these compounds. The present results of ac and dc magnetization, electrical resistivity and heat-capacity measurements down to 1.8 K establish that these compounds undergo antiferromagnetic order initially, followed by complex spin-glass features with decreasing temperature. These characteristic temperatures are: For …
A study investigating the effect of Sn substitution on the magnetocaloric properties of Mn$ _{3} $Ga$ _{(1-x)} $Sn$ _{x} $C compounds reveals that nature of the MCE has a strong dependence on the nature of the magnetic ordering. For small amounts of Sn ($ x\leq0.2 $) the MCE is of the inverse type wherein an increase in the applied field beyond 5T gives rise to a table like temperature dependence of the entropy due to a coupling between the first order FM - AFM transition and the field induced AFM - FM transition. Replacement of Ga by larger concentrations of Sn ($ x\geq0.71 $) $(ΔS_M)$ result…
