Inverse Magnetocaloric Effect Research Articles

Investigation of the inverse magnetocaloric effect with the fraction method

In this study, we examine Ni49Nb1Mn36In14 (nom. at.%) magnetic shape memory alloy (MSMA) to illustrate the inverse magnetocaloric effect (MCE) using the fraction method. The magnetic entropy change, , was calculated with both, the fraction method and the thermomagnetic Maxwell relation. Our results demonstrate that there exists a large magnetization difference between field-cooling and field-heating histories in Ni49Nb1Mn36In14 (nom. at.%) MSMA, which can be attributed to the pinning of lattice entropy and magnetic entropy, as it is well-known that the temperature and applied magnetic fields have an opposing effect on the total entropy change. In addition, we describe the inverse MCE and the contradictory roles on the total entropy change between the two stimuli via the fraction method.

Tunable magnetism and large inverse magnetocaloric effect in Shastry-Sutherland compounds Tb2Be2Si1-xGexO7 (0 ≤ x ≤ 1)

The structure, magnetism and magnetocaloric effect (MCE) have been systematically investigated on the series of Tb2Be2Si1-xGexO7 (0 ≤ x ≤ 1) compounds, where the magnetic Tb3+ ions are located on the quasi-two-dimensional Shastry−Sutherland-Lattice (SSL). The X-ray diffraction measurements reveal that all compounds crystallize into the tetragonal structure with space group P4¯21m, the lattice parameters and nearest neighbor Tb-Tb distances increase monotonically with the variation of doping content x. All samples show the antiferromagnetic (AFM) ordered ground state and field (μ0H) induced spin-flop (SP) transitions below Néel temperature (TN). Moreover, the constructed field-temperature (μ0H−T) phase diagrams of Tb2Be2Si1-xGexO7 (0 ≤ x ≤ 1) reveal that the AFM phase shifts to the low temperature and low field sides with increased x. Below TN, we can observe a crossover behavior of MCE from the low-field (Δμ0H<2.58 T) inverse MCE (IMCE) to the CMCE at high fields (Δμ0H>2.58 T). Among these serial compounds, Tb2Be2SiO7 exhibits the maximal IMCE with a value of 8.30 J kg−1 K−1 under Δμ0H= 0.7 T and 2 K, comparable to the MCE (8.6 J kg−1 K−1) of the benchmark material Tb3Ga5O12 at Δμ0H = 2 T. Additionally, it has a slightly better MCE performance than the materials RE3Ga5O12 (RE = Dy, Tb, Gd) under Δμ0H = 2 T. The realization of large IMCE performance for Tb2Be2SiO7 provides an alternative route for magnetic refrigeration at low field and liquid Helium temperatures.

Magnetic and Magnetocaloric Characteristics of the Mn1.9Cu0.1Sb Alloy

The magnetic and magnetocaloric characteristics of the Mn1.9Cu0.1Sb alloy were studied. The presence of a relatively sharp decrease in the magnetization in the region of 100 K is established, which, according to ab initio calculations, can be interpreted as antiferromagnetism–ferrimagnetism transitions. The presence of a magnetic phase transition from a ferrimagnetic to an antiferromagnetic state (F ↔ AF) leads to the appearance of an inverse magnetocaloric effect, which is preserved in magnetic fields up to 10 T.

Inverse Magnetocaloric Effect in Mn5Si3 Compound

A direct method was used to study the magnetocaloric effect (MCE) for samples of the compound Mn5Si3 under adiabatic conditions in magnetic fields up to 2 T at cryogenic temperatures in the range from 25 to 125 K. According to the results of measurements, it is shown that at temperatures near the first-order metamagnetostructural phase transition from a noncollinear antiferromagnetic to a collinear antiferromagnetic state, both inverse and сonventional MCE are observed. The maximum value of the inverse MCE was ΔTad = –0.27 K at initial temperature T0 = 55 K in a magnetic field of 2 T. Conventional MCE with maximum value ΔTad = +0.23 K is observed at T0 = 70 K in a field of 2 T.

Theoretical investigation of direct and inverse magnetocaloric effect in La2FeMn1-xCuxO6 and Sr2RuMn1-xFexO6 using a phenomenological model

This letter presents a theoretical work on magnetocaloric properties of two series of double perovskites compounds La2FeMn1-xCuxO6 and Sr2RuMn1-xFexO6 with four different concentrations (x = 0, 0.1, 0.2 and 0.3) synthesized by solid state method. The value of the magnetocaloric effect (MCE) of both the series has been predicted by applying a phenomenological model on temperature variation magnetization data of the compounds. Along with the maximum entropy change (−ΔSm)max, specific heat and relative cooling power (RCP) were also calculated using the model. Interestingly, the simulated MCE of Fe doped Sr2RuMnO6 (Sr2RuMn1-xFexO6) showed the coexistence of direct and inverse MCE.

Magnetoelastic coupling with inverse magnetocaloric effect observed in Sr2YRuO6

Sr2YRuO6, a 4d transition metal, Ru ion based double perovskite crystallizes in monoclinic structure with Y and Ru octahedra ordering alternately. The relevance of lattice distortion to complex magnetic ground state is investigated from structural, vibrational, magnetic, transport and thermal properties. Raman modes due to monoclinic distortions are observed. From the temperature dependent magnetization studies, a magnetic transition is observed at 25 K and below that the presence of weak ferromagnetic contribution is noticed. A magnetic frustration parameter of six is evaluated from the magnetic results that suggest the presence of spin frustration on the Ru octahedra leading to geometric frustration in SYRO. Isothermal magnetization measurements are carried out for several temperatures from 8 K to 70 K in small temperature intervals to determine the magnetocaloric effect of Sr2YRuO6. The change in magnetic entropy around the Neel temperature, 25 K and Inverse magnetocaloric effect is observed in the system around this temperature. The change in isothermal magnetic entropy results indicates a canted AFM structure as the ground state. Neutron diffraction data refined using propagation vector, k = (0.5,0.5,0) reveal antiferromagnetic ordering at temperatures below 30 K down to 2 K. Variation of the lattice parameters with temperature from the neutron powder diffraction result signifies the presence of magnetoelastic coupling around 25 K. From the temperature dependent resistivity measurements, a small polaron hopping like conductivity is observed in the system. Activation energy reduces with the increase in temperature. Temperature dependent specific heat data shows no ordering, the absence of peak around magnetic transition along with magnetic contribution well above transition temperature is consistent with magnetic frustration in this system.

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.

Residual entropy and magnetocaloric effect in a diluted sawtooth spin model of hole-doped CuO chains.

Ground-state and magnetocaloric properties of a site-diluted sawtooth magnetic chain in the presence of an external magnetic field are exactly investigated by using the transfer-matrix method. The model captures the main magnetic interactions along CuO chains present in some hole-doped cuprates. The ground-state diagram is exhibited and analytical expressions for the residual entropy within each ground state and along the transition lines are derived. We explicitly discuss the role of the underlying pairing correlations and the entropy maximization principle. The isothermal entropy change is determined as a function of interaction parameters, doping concentration, and magnetic-field amplitude. Normal and inverse magnetocaloric effects are reported. Adiabatic demagnetization curves are discussed in connection with configurational and spin contributions to the residual entropy.

Investigation on Magnetization, Magnetocalory, Magnetoresistance, and Electric Properties of Ni-Mn Based Heusler Alloy

The magnetic and electrical characteristics of Ni-Mn quinary Heusler alloys are studied in the current work. The results concern the materials’ magnetic and electrical behavior. The physical property measurement system (PPMS) and superconducting quantum interference device (SQUID) were used at various magnetization levels to determine the results. The addition of Fe helps to form the alloy into a smart memory alloy with magnetocrystalline anisotropy, twin border mobility, and varied magnetic and martensite transition temperature characteristics. Character changes in the superparamagnetic (SPM) and paramagnetic (PM) alloys occur between 26 and 34 °C. The curves are supported by the alloy’s martensitic transition temperature change. A large refrigeration capacity is identified in the alloy. These properties are an indication of the alloys’ application prospects. Entropy change helps to detect the inverse magnetocaloric effect in the alloy, whereas adiabatic temperature change helps identify the origin and validity of reverse magnetic properties. The transition temperature changes occur when austenite’s sigma is larger than that of martensite, and as the magnetic field increases, the temperature declines. Isothermal magnetization curves, a large (MR)/B value at low and high magnetic fields, and temperatures near the transformation point suggest that small-crystal Heusler alloys have tremendous promise for low and high magnetic field magnetoresistance applications.

Observation of conventional and inverse magnetocaloric effects in (Dy$$_{0.6}$$Gd$$_{0.4}$$)$$_{5}$$Pd$$_{2}$$

Observation of conventional and inverse magnetocaloric effects in (Dy$$_{0.6}$$Gd$$_{0.4}$$)$$_{5}$$Pd$$_{2}$$

Development and magnetocaloric properties of Ni(Co)-Mn-Sn printing ink

Magnetocaloric (MC) cooling is a vast research field nowadays which needs continuing development of MC materials. Besides, technological approaches of the fabrication and design of MC materials to be applied as the heat exchangers require a reinforcement. Heusler-type metamagnetic shape memory alloys (MetaMSMAs) exhibiting a large MC effect near room temperature, owing to the magnetic field induced first-order transformation, have been shown to be promising candidates for magnetic refrigeration, and the possibility of their fabrication by 3D printing technologies was experimentally demonstrated in the literature. In the present work we have elaborated a route for the room-temperature fabrication of MC ink incorporating the polymer binder and Ni(Co)-Mn-Sn MetaMSMA powder obtained from the preliminary melt-spun ribbon with tuned MC properties. The ink is used to print 2D films which do not require a subsequent heat treatment. The field-induced adiabatic temperature measurements reveal that the screen-printed samples displayed the same inverse MC effect as the ribbon, evidencing that room-temperature ink printing technology of MC intermetallics, elaborated for the first time in the present work, is promising for 2D printing of cooling microdevices for MEMS, flexible electronics etc. • A magnetocaloric powder based on metamagnetic shape memory alloys for additive manufacturing has been successfully obtained. • A magnetocaloric ink was developed using a sustainable approach, avoiding any hazardous product during its preparation. • Magnetocaloric materials printed by screen-printing technique show performance similar to that observed in the bulk ribbon.

Magnetic properties and magnetocaloric effect of R2Fe14B compounds with R = Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho and High-Magnetic field phase transitions in the compounds with R = Gd, Dy

The temperature and field dependences of the: magnetization, magnetic specific heat and magnetic entropy of the R2Fe14B compounds, are studied using the mean-field two-sublattice model, where R = Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and B is boron. The isothermal entropy change ΔSm and the adiabatic temperature change ΔTad are calculated, for magnetic fields ≤ 5 T, by a Maxwell’s relation and a well-known integration involving the total heat capacity. The temperature range for these calculations is up to 700 K. Direct magnetocaloric effect (MCE), in all compounds, is present with maximum ΔSm and ΔTad in the range of 0.9–6.8 J/mol. K and 1.5–7.7 K, respectively, for a magnetic field change in the range of 1–5 T. The relative cooling power RCP(S) is in the range of 196–526 J/ kg. Ferrimagnetic compounds show both direct and small inverse MCE. It is found that Pr2Fe14B has the highest ΔSm of 6.8 J/mol. K and the largest ΔTad of 7.7 K at a magnetic field change of 5 T. The magnetization curves are calculated for Dy2Fe14B for temperatures in the range of 30–200 K and for Gd2Fe14B from 46 to 400 K for magnetic fields up to 300 T. It is found that these two compounds exhibit ferrimagnetic to ferromagnetic first-order phase transitions. Belov -Arrott plots, for these two compounds, show S-shaped feature which supports the occurrence of a first-order phase transition.

Magneto-structural coupling induced multiple magnetic transitions and magnetocaloric effect of Ni43Mn46Sn9Ge2 alloy

Multiple magnetic and structural phase transitions and magnetocaloric effect of Ni43Mn46Sn9Ge2 Heusler alloy were detailedly investigated. The martensitic and inverse-martensitic transitions occur at temperatures slightly below room temperature, which induces a ferromagnetic - antiferromagnetic transition and large inverse magnetocaloric effect. A paramagnetic - ferromagnetic and antiferromagnetic - ferromagnetic transition was observed in high-temperature austenitic and low-temperature martensitic phase, respectively. The evident thermomagnetic irreversibility at low temperatures of the martensitic phase suggests a reentrant spin glass state, which originates from the frustration of the competing ferromagnetic and antiferromagnetic spins and results in the visible exchange bias, large coercivity and double-shifted hysteresis behaviors. A T-μ0H phase diagram was finally constructed.

Enhanced Relative cooling Power and large inverse magnetocaloric effect of cobalt ferrite nanoparticles synthesized by auto-combustion method

This work focuses on the microstructure, magnetic properties and magnetocaloric effect of CoFe2O4 (CFO) nanoparticles elaborated by the sol–gel auto combustion method. The XRD investigation indicates that CFO is crystallized in a cubic spinel structure with the Fd3¯m space group and the SEM micrograph shows fine quasi-spherical nanoparticles with an average grain size of 160 nm. The temperature dependence of the Raman spectra reveals the ferromagnetic to paramagnetic conversion started from 723 K. The magnetization temperature dependence reveals the Curie temperature at TC = 785 K. Large value of magnetocaloric temperature change of ΔT = 11.2 K with a high RCP of 687.56 J Kg−1 were measured indirectly via the Maxwell approach making our CFO nanopowder suitable candidate for both environmentally friendly magnetic refrigeration and medical applications at ambient temperature.

Quadrupole Ordering and Inverse Magnetocaloric Effect in a Magnet with Biquadratic Exchange and Spin S = 1

Quadrupole Ordering and Inverse Magnetocaloric Effect in a Magnet with Biquadratic Exchange and Spin S = 1

Magnetic, thermal, and magnetocaloric properties of the holmium trialuminide HoAl3 with polytypic phases

We investigate the magnetic, thermal, and magnetocaloric properties of the intermetallic HoAl3 compounds with two different crystal structures. The room-temperature equilibrium trigonal phase HoAl3 undergoes an antiferromagnetic (AFM) transition at the Néel temperature TNtri= 9.8 K. The AFM order of the compound is strong against the magnetic field, so that inverse magnetocaloric effect (MCE) is found even under a magnetic field change of 0–50 kOe. The high-pressure cubic phase HoAl3, prepared by a rapid-solidification process, is antiferromagnetically ordered below TNcub= 15 K. Magnetic and specific heat measurements reveal that this long-range AFM state becomes unstable as the temperature drops and then is replaced by a magnetic glassy state below a spin freezing temperature Tf= 11 K. The successive changes in magnetic state result in complicated temperature and field dependence of the MCE at low temperatures.

Direct and inverse magnetocaloric effects in FeRh alloy

There are two types of magnetocaloric effects that are the so-called direct and inverse effects originating from ferromagnetic–paramagnetic (FM–PM) and antiferromagnetic–ferromagnetic (AFM–FM) phase transitions, respectively. Here, the magnetocaloric effects of FeRh alloy, which exhibit both the direct and inverse effects, have been studied by combining first-principles calculations and Monte Carlo simulations. The magnetic exchange coupling constants in the AFM and FM phases are evaluated by first-principles calculations based on the Liechtenstein formula. The Monte Carlo calculations considering the two-phase mixtures of AFM and FM well reproduce the experimental magnetization curves at zero external magnetic field. It is also shown that the isothermal magnetic entropy changes near the AFM–FM transition temperature under magnetic fields are successfully reproduced based on the Maxwell relation. The entropy changes in a wide range of the magnetic fields near the AFM–FM and FM–PM transition temperatures are investigated and the direct and inverse magnetocaloric effects of FeRh are discussed. The giant relative cooling power of FeRh alloy is achieved due to the large saturation magnetizations and the first-order AFM–FM phase transition.

Inverse Magnetocaloric Effect and Kinetic Arrest Behavior in As-Cast Gd2In at Cryogenic Temperatures

Inverse Magnetocaloric Effect and Kinetic Arrest Behavior in As-Cast Gd2In at Cryogenic Temperatures

From conventional to inverse magnetocaloric effect in GdMn1-x Cr x O3

In this work, a phenomenological model (PM) is used to simulate the magnetocaloric effect (MCE) of GdMn1-x Cr x O3 (0 ≤x ≤0.4) (GMCO) samples through the modelling of experimental isofield thermo-magnetization curves. The results showed that the MCE of GMCO samples depends strongly on Cr content, achieving a conventional MCE for low Cr content (level of doping x ≤ 0.3). However, the MCE of a higher Cr content sample has an inverse MCE. The behaviour of MCE in GMCO samples indicated that GMCO compounds are interesting magnetocaloric materials and can fruitfully be functioned as cryogenic magnetic refrigerants below 40 K especially in radiation detectors for outer space research.

Bulk-like first-order magnetoelastic transition in FeRh particles

Near-equiatomic, chemically-ordered iron-rhodium (FeRh) alloy is a fundamentally interesting material that may become useful in niche applications making use of its unique magneto functional phenomena, for example, the giant inverse magnetocaloric effect near room temperature that is associated with a sharp first-order magnetic phase transition. The nearly discontinuous antiferromagnetic-ferromagnetic phase transformation in bulk FeRh is well-known; however, the transition broadens considerably in fine particles and films with thickness less than 50 nm, precluding their potential applications. Here, we report an abrupt, bulk-like first-order magnetoelastic transformation in powders consisting of sub-micron particles of nearly equiatomic FeRh compound synthesized via solid-state mechanochemical co-reduction of FeF2 and RhCl3 and subsequent heat treatments. We demonstrate that annealing at temperatures ranging from 600 ̊C to 800 ̊C enables tailoring phase content, particle size, and magnetic properties of the powders. A maximum magnetic-field-induced entropy change of ~10 J/kg K at μ0ΔH = 1 T has been achieved in powders annealed at 800 ̊C. The retention of extraordinary responsiveness in sub-micron particles of FeRh is likely to open doors for system component fabrication using additive manufacturing methods, along with new opportunities to employ FeRh in theranostics.