Magnetic and magnetocaloric effect of Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass

Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass exhibited excellent magnetic refrigeration material with a wide temperature range and high refrigeration capacity(RC)was reported.Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass was observed with typical spin glass behavior around 15.5 K.In addition,we find that the magnetic entropy change(-△S_(M))originates from the sample undergoing a ferromagnetic(FM)to paramagnetic(PM)transition around 20 K.Under a field change from 0 T to 7 T,the value of maximum magnetic entropy change(-△S_(M)^(max))reaches 12.5 J/kg·K,and the corresponding value of RC reaches 487.7 J/kg in the temperature range from 6 K to 60 K.The large RC and wide temperature range make the Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass be a promising material for application in magnetic refrigerators.

Gd-based molecular coolants:Aggregating for better magnetocaloric effect

Two series of 3d-Gd mixed-metal phosphonate complexes with either only two gadolinium centers such as{Gd2},{Ni2Gd2},{Co4Gd2},{Co8Gd2},{Fe6Gd2},and{Fe17Gd2}or more than two gadoliniums such as{Co8Gd4},{Mn8Gd4},{Co4Gd6},{Mn4Gd6},{Co6Gd8},{Ni5Gd8},{Ni6Gd6},{Co8Gd8},and{Mn9Gd9}have been solvothermally prepared and magnetothermally studied.The nearly identical environments of the Gd(III)dimer in thefirst series allow us to qualitatively analyze the effect of magnetic exchange coupling on the magne-tocaloric effect(MCE).By doubling,tripling,or quadrupling of the Gd(III)centers,the second series of 3d-Gd mixed-metal complexes was built to further test the other effects of exchange couplings on MCE in more complicated circumstances.For the antiferromagnetic coupling cases,the results are nearly identical but diversify when topological spin frustrations are created,whose massive low-lying excited spin states help enhance MCE.For presumably ferromagnetically coupled ones,albeit are rare in phosphonate complexes,they do exhibit excellent MCE.Meanwhile,the com-plexes with weakly coupled metal centers serve as excellent examples for studying the effect of molecular mass on MCE when its magnitude is expressed in the unit of Joule per kilogram,from which we can see the values are directly proportional to the percentage of the Gd(III)ions in molecular weight.

Magnetism, heat capacity, magnetocaloric effect, and magneto-transport properties of heavy fermion antiferromagnet CeGaSi

We synthesize high-quality single crystal of CeGaSi by a Ga self-flux method and investigate its physical properties through magnetic susceptibility,specific heat and electrical resistivity measurements as well as high pressure effect.Magnetic measurements reveal that an antiferromagnetic order develops below T_(m)~10.4 K with magnetic moments orientated in the ab plane.The enhanced electronic specific heat coefficient and the negative logarithmic slope in the resistivity of CeGaSi indicate that the title compound belongs to the family of Kondo system with heavy fermion ground states.The max magnetic entropy change-ΔS_(M)^(max)(μ_(0)H⊥c,μ_(0)H=7 T) around T_(m) is found to reach up to 11.85 J·kg^(-1)·K^(-1).Remarkably,both the antiferromagnetic transition temperature and-ln T behavior increase monotonically with pressure applied to 20 kbar(1 bar=10~5 Pa),indicating that much higher pressure will be needed to reach its quantum critical point.

Study of the Magnetocaloric Effect in La0.5Sm0.2Sr0.3Mn1-xFexO3 (x = 0 and 0.05) Manganites with the Mean-Field Theory

In this paper, the magnetocaloric in La0.5Sm0.2Sr0.3Mn1-xFexO3 compounds with x = 0 (LSSMO) and x = 0.05 (LSSMFO) were simulated using mean field model theory. A strong consistency was observed between the theoretical and experimental curves of magnetizations and magnetic entropy changes, −ΔSM(T). Based on the mean-field generated −ΔSM(T), the substantial Temperature-averaged Entropy Change (TEC) values reinforce the appropriateness of these materials for use in magnetic refrigeration technology within TEC (10) values of 1 and 0.57 J∙kg−1∙K−1under 1 T applied magnetic field.

Structure, magnetism and magnetocaloric effects in Er_(5)Si_(3)B_(x)(x=0.3,0.6) compounds

We investigate the structure, magnetic properties, magnetic phase transitions and magnetocaloric effects(MCEs) of Er5Si3Bx(x=0.3,0.6) compounds. The Er5Si3Bx(x = 0.3, 0.6) compounds crystalize in a Mn5Si3type hexagonal structure(space group: P63/cm) and exhibit a successive complicated magnetic phase transition. The extensive magnetic phase transitions contribute to the broad temperature range of MCEs exhibiting in Er_(5)Si_(3)B_(x)(x=0.3,0.6) compounds, with maximum magnetic entropy change(-ΔSM_(max)) and refrigeration capacity of 10.2 J·kg^(-1)·K^(-1), 356.3 J/kg and 11.5 J·kg^(-1)·K^(-1),393.3 J/kg under varying magnetic fields 0–5 T, respectively. Remarkably, the δTFWHMvalues(the temperature range corresponding to 1/2×|-ΔSM_(max)|) of Er5Si3Bx(x=0.3,0.6) compounds were up to 41.8 K and 39.6 K, respectively. Thus, the present work provides a potential magnetic refrigeration material with a broad temperature range MCEs for applications in cryogenic magnetic refrigerators.

Giant low-field cryogenic magnetocaloric effect in polycrystalline LiErF4 compound

Antiferromagnetic LiErF4has attracted extensive attention due to its dipolar interaction domination and quantum fluctuations action. In the present work, the crystal structure, cryogenic magnetic properties, and magnetocaloric effect(MCE) of polycrystalline LiErF4compound are investigated. Crystallographic study shows that the compound crystallizes in the tetragonal scheelite structure with I41/a space group. It exhibits an antiferromagnetic(AFM) phase transition around 0.4 K, accompanied by a giant cryogenic MCE. At 1.3 K, the maximum values of magnetic entropy changes are 24.3 J/kg·K,33.1 J/kg·K, and 49.0 J/kg·K under the low magnetic field change of 0–0.6 T, 0–1 T, and 0–2 T, respectively. The giant MCE observed above Néel temperature TNis probably due to the strong quantum fluctuations, which cause a large ratio of the unreleased magnetic entropy existing above the phase transition temperature. The outstanding low-field MCE below 2 K makes the LiErF4compound an attractive candidate for the magnetic refrigeration at the ultra-low temperature.

Magnetocaloric effect in Ni-Mn-In-Co microwires prepared by Taylor-Ulitovsky method

Ni-Mn-In-Co microwires with diameter of 30-100 μm are prepared by glass-coated metal filaments（Taylor–Ulitovsky） method. The effects of magnetic field on martensite transformation temperature in the as-prepared and annealed microwires are investigated using a physical property measurement system（PPMS）. Magnetocaloric effect（MCE） attributed to field-induced austenite transformation in the as-prepared and annealed microwires is analyzed indirectly from the isothermal magnetization（M-B） curves. The as-prepared microwire has a 7-layer modulated martensite structure（7M） at room temperature. The changes of austenite starting temperature induced by an external magnetic field（ΔAs/ΔB） in the as-prepared and annealed microwires are-1.6 and-4 K/T, respectively. Inverse martensite to austenite transformation exists in annealed microwires when an external magnetic field is applied at temperatures near As. The entropy change（ΔS） obtained in the annealed microwires is 3.0 J/（kg·K）, which is much larger than that in the as-prepared microwires 0.5 J/（kg·K）. The large entropy change and low price make Ni-Mn-In-Co microwires a potential working material in magnetic refrigeration.

Magnetocaloric effects in RT X intermetallic compounds(R = Gd–Tm, T = Fe–Cu and Pd, X = Al and Si)

The magnetocaloric effect（MCE） of RT Si and RT Al systems with R = Gd–Tm, T = Fe–Cu and Pd, which have been widely investigated in recent years, is reviewed. It is found that these RT X compounds exhibit various crystal structures and magnetic properties, which then result in different MCE. Large MCE has been observed not only in the typical ferromagnetic materials but also in the antiferromagnetic materials. The magnetic properties have been studied in detail to discuss the physical mechanism of large MCE in RT X compounds. Particularly, some RT X compounds such as Er Fe Si,Ho Cu Si, Ho Cu Al exhibit large reversible MCE under low magnetic field change, which suggests that these compounds could be promising materials for magnetic refrigeration in a low temperature range.

Review of magnetic properties and magnetocaloric effect in the intermetallic compounds of rare earth with low boiling point metals

The magnetocaloric effect （MCE） in many rare earth （RE） based intermetallic compounds has been extensively in- vestigated during the 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 on studying the 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 exhibit promising MCE properties, which make them attractive for low temperature magnetic refrigeration. Characteristics of the magnetic transition, origin of large MCE, as well as the potential application of these compounds are thoroughly discussed. Additionally, a brief review of the magnetic and magnetocaloric properties in the quaternary rare earth nickel boroncarbides RENi2B2C superconductors is also presented.

Effect of R substitution on magnetic properties and magnetocaloric effects of La_(1-x)R_xFe_(11.5)Si_(1.5) compounds with R=Ce,Pr and Nd

Magnetic properties and magnetocaloric effects of La1-xRxFe11.5Si1.5 （R=Pr, （0 ≤ x ≤ 0.5）; R = Ce and Nd, （0 ≤ x ≤ 0.3）） compounds are investigated. Partially replacing La with R = Ce, Pr and Nd in La1-xRxFe11.5Si1.5 leads to a reduction in Curie temperature due to the lattice contraction. The substitution of R for La causes an enhancement in field-induced itinerant electron metamagnetic transition, which leads to a remarkable increase in magnetic entropy change ASm and also in hysteresis loss. However, a high effective refrigerant capacity RCeff is still maintained in La1-xRxFe11.5Si1.5. In the present samples, a large △Sm and a high RCeff have been achieved simultaneously.

Influence of carbon on the giant magnetocaloric effect of LaFe_11.7Si_1.3

The influences of carbon on phase formation, Curie temperature, and magnetic entropy change of the NaZn13-type LaFe11.7Si1.3 were investigated. Seven carbon-containing alloys, LaFe11.7Si1.3Cx with x = 0, 0.03, 0.06, 0.10, 0.20, 0.30, and 0.50, respectively, were prepared for this investigation. Experimental results show that addition of a small amount of carbon in LaFe11.7Sil.3 is favorable for the formation of the NaZn13-type structure of LaFe11.7Si1.3Cx. The lattice constant increases with C addition and x increases in the alloy because of the introduction of C as interstitial atoms. The Curie temperature of LaFe11.7Si1.3Cx increases from 194 K to 225 K as x increases from 0 to 0.5. Large magnetic entropy changes were observed in these carbon-containing alloys LaFe11.7Si1.3Cx because of their first-order structural/magnetic transition. The maximum magnetic entropy change of 27.5 J.kg^-1K^-1 at 202 K for the 0-1.56 T magnetic field change was observed in the alloy with x = 0.06. The large magnetic-entropy changes corresponding to low magnetic field change, and the low cost of the material of LaFe11..7Si1.3Cx makes it a promising candidate to be used as magnetic refrigerants in the corresponding temperature range.

Low field induced giant anisotropic magnetocaloric effect in DyFeO_3 single crystal

We have investigated the anisotropic magnetocaloric effect and the rotating field magnetic entropy in Dy FeO3 single crystal. A giant rotating field entropy change of -ΔSM^R = 16.62 J/kg·K was achieved from b axis to c axis in bc plane at 5 K for a low field change of 20 k Oe. The large anisotropic magnetic entropy change is mainly accounted for the 4 f electron of rare-earth Dy^3＋ ion. The large value of rotating field entropy change, together with large refrigeration capacity and negligible hysteresis, suggests that the multiferroic ferrite Dy FeO3 singlecrystal could be a potential material for anisotropic magnetic refrigeration at low field, which can be realized in the practical application around liquid helium temperature region.

Magnetic properties and magnetocaloric effects in NaZn_(13)-type La(Fe,Al)(13)-based compounds

In this article, our recent progress concerning the effects of atomic substitution, magnetic field, and temperature on the magnetic and magnetocaloric properties of the LaFe13-xAlx compounds are reviewed. With an increase of the aluminum content, the compounds exhibit successively an antiferromagnetic （AFM） state, a ferromagnetic （FM） state, and a mictomagnetic state. Furthermore, the AFM coupling of LaFe13 -xAlx can be converted to an FM one by substituting Si for A1, Co for Fe, and magnetic rare-earth R for La, or introducing interstitial C or H atoms. However, low doping levels lead to FM clusters embedded in an AFM matrix, and the resultant compounds can undergo, under appropriate applied fields, first an AFM-FM and then an FM-AFM phase transition while heated, with significant magnetic relaxation in the vicinity of the transition temperature. The Curie temperature of LaFe13-xAlx can be shifted to room temperature by choosing appropriate contents of Co, C, or H, and a strong magnetocaloric effect can be obtained around the transition temperature. For example, for the LaFel 1.5All.5Co.2Hl.o compound, the maximal entropy change reaches 13.8 J.kg-1.K-1 for a field change of 0-5 T, occurring around room temperature. It is 42% higher than that of Gd, and therefore, this compound is a promising room-temperature magnetic refrigerant.

Effect of gallium doping on the magnetocaloric effect of LaFe_(11.2)Co_(0.7)Si_(1.1)

The lattice parameter and magnetocaloric properties of three samples of LaFe11.2Co0.7Si1.1-xGax with x = 0, 0.03 and 0.05 have been investigated by X-ray powder diffraction and magnetization measurements. The lattice parameter increases slightly and the Curie temperature increases somewhat with increasing gallium content. However, a small amount of Ga doping into the sample decreases the magnetic entropy change of the sample. All the samples remain in the first-order magnetic phase transition. The most striking effect of the Ga doping is that the cooling capacity in the samples increases significantly. The maximum magnetic entropy change, ASM and the cooling capacity of the sample LaFe11.2Co0.7Si1.07Ga0.03 are 11.9 J·kg^-1·K^-1 and 254.8 J·kg^-1, respectively.

Magnetic properties, magnetoresistivity and magnetocaloric effect in Gd_xLa_(1-x)-MnSi alloys

The results of magnetization, magnetoresistivity and magnetocalofic effect （MCE） studies performed on polycrystalline samples of the GdxLa1-xMnSi （x=0.5, 0.6, 0.7, 0.8, 0.9, 1.0） compounds were presented. Complex measurements were carried out on the GdxLa1-xMnSi compounds to determine the influence of substitution in the rare earth （R） sublattice on the magnetic and related properties of these compounds. The compounds with x≤0.6 demonstrated two magnetic phase transitions （ferromagnetic to paramagnetic and antiferro- magnetic to ferromagnetic） both of which were first order. Anomalies in the magnetocaloric effect, electroresistivity and magnetoresistivity were observed in the temperature ranges of the magnetic phase transitions. The temperature dependences of MCE and magnetoresistivity for these compounds correlated with the temperature dependence of magnetization.

Giant magnetocaloric effect in the Gd_5 Ge_(2.025)Si_(1.925)In_(0.05) compound

The magnetocaloric properties of the GdsGe2.025Si1.925In0.05 compound have been studied by x-ray diffraction, magnetic and heat capacity measurements. Powder x-ray diffraction measurement shows that the compound has a dominant phase of monoclinic Cd5Ge2Si2-type structure and a small quantity of Gds（Ge,Si）3-type phase at room temperature. At about 270 K, this compound shows a first order phase transition. The isothermal magnetic entropy change （△SM） is calculated from the temperature and magnetic field dependences of the magnetization and the temperature dependence of MCE in terms of adiabatic temperature change （△Tad） is calculated from the isothermal magnetic entropy change and the temperature variation in zero-field heat-capacity data. The maximum △SM is -13.6 J·kg^-1.K^- 1 and maximum ATad is 13 K for the magnetic field change of 0 5 T. The Debye temperature （θD） of this compound is 149 K and the value of DOS at the Fermi level is 1.6 states/eV.atom from the low temperature zero-field heat-capacity data. A considerable isothermal magnetic entropy change and adiabatic temperature change under a field change of 0-5 T jointly make the Gd5Ge2.025Si1.925In0.05 compound an attractive candidate for a magnetic refrigerant.

Structure and magnetocaloric effect in melt-spun La(Fe,Si)_(13) and MnFePGe compounds

The magnetocaloric properties of melt-spun La(Fe,Si)13 and MnFePGe compounds were investigated. Very large value of magnetic entropy change ｜ΔS｜=31 and 35.4 J·(kg·K)-1 under 5 T were obtained at 201 K in LaFe11.8Si1.2 melt-spun ribbons and at around 317 K in Mn1.1Fe0.9P0.76Ge0.24 melt-spun ribbons, respectively. The large magnetocaloric effect results from a more homogenous element distribution related to the very high cooling rate during melt-spinning. The excellent MCE properties, the low materials cost and the accelerated aging regime make the melt-spun-type La(Fe,Si)13 and MnFePGe materials an excellent candidate for magnetic refrigerant applications.

Magnetocaloric and barocaloric effects in a Gd_5Si_2Ge_2 compound

The first-order phase transition in GdsSi2Ge2 is sensitive to both magnetic field and pressure. It may indicate that the influences of the magnetic field and the pressure on the phase transition are virtually equivalent. Moreover, theoretical analyses reveal that the total entropy change is almost definite at a certain Curie temperature no matter whether the applied external field is a magnetic field or a pressure. The entropy change curve can be broadened dramatically under pressure, and the refrigerant capacity is improved from 284.7 J/kg to 447.0 J/kg.

The magnetic properties and magnetocaloric effects in binary R-T(R = Pr,Gd,Tb,Dy,Ho,Er,Tm;T = Ga,Ni,Co,Cu)intermetallic compounds

In this paper, we review the magnetic properties and magnetocaloric effects（MCE） of binary R–T（R = Pr, Gd, Tb,Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series, R_（12）Co_7 series, R_3 Co series and RCu_2series）, which have been investigated in detail in the past several years. The R–T compounds are studied by means of magnetic measurements, heat capacity measurements, magnetoresistance measurements and neutron powder diffraction measurements. The R–T compounds show complex magnetic transitions and interesting magnetic properties.The types of magnetic transitions are investigated and confirmed in detail by multiple approaches. Especially, most of the R–T compounds undergo more than one magnetic transition, which has significant impact on the magnetocaloric effect of R–T compounds. The MCE of R–T compounds are calculated by different ways and the special shapes of MCE peaks for different compounds are investigated and discussed in detail. To improve the MCE performance of R–T compounds,atoms with large spin（S） and atoms with large total angular momentum（J） are introduced to substitute the related rare earth atoms. With the atom substitution, the maximum of magnetic entropy change（？SM）, refrigerant temperature width（Twidth）or refrigerant capacity（RC） is enlarged for some R–T compounds. In the low temperature range, binary R–T（R = Pr, Gd,Tb, Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series,R_（12）Co_7 series, R_3 Co series and RCu_2series） show excellent performance of MCE, indicating the potential application for gas liquefaction in the future.

Magnetocaloric Effect in Colossal Magnetoresistance Material (La_(0.6)Dy_(0.1))Sr_(0.3)MnO_3

The magnetocaloric effect in the A-site doping colossal magnetoresistance material (La_(0.6)Dy_(0.1))Sr_(0.3)MnO_3 was studied. From the measurement and calculation of isothermal magnetization (M-H) curves under various temperatures, a large magnetocaloric effect with ferromagnetic-paramagnetic transition, additional magnetism exchange action introduces additional magnetic entropy change was discovered. This result suggests that (La_(0.6)Dy_(0.1))Sr_(0.3)MnO_3 is a suitable candidate as working substance at room temperature in magnetic refrigeration technology.