Correction: Correction: Influence of Ni content on structural, magnetocaloric and electrical properties in manganite La0.6Ba0.2Sr0.2Mn1-xNixO3 (0 ≤ x ≤ 0.1) type perovskites.

[This corrects the article DOI: 10.1039/D3RA90093B.][This corrects the article DOI: 10.1039/D1RA07059B.].

Correction: Influence of Ni content on structural, magnetocaloric and electrical properties in manganite La0.6Ba0.2Sr0.2Mn1-xNixO3 (0 ≤ x ≤ 0.1) type perovskites.

[This corrects the article DOI: 10.1039/D1RA07059B.].

Influence of Ni content on structural, magnetocaloric and electrical properties in manganite La0.6Ba0.2Sr0.2Mn1-x Ni x O3 (0 ≤ x ≤ 0.1) type perovskites.

We present a detailed study on the physical properties of La0.6Ba0.2Sr0.2Mn1-x Ni x O3 samples (x = 0.00, 0.05 and 0.1). The ceramics were fabricated using the sol-gel route. Structural refinement, employing the Rietveld method, disclosed a rhombohedral R3̄c phase. The magnetization vs. temperature plots show a paramagnetic-ferromagnetic (PM-FM) transition phase at the T C (Curie temperature), which decreases from 354 K to 301 K. From the Arrott diagrams M 2 vs. µ 0 H/M, we can conclude the phase transition is of the second order. Based on measurements of the isothermal magnetization around T C, the magnetocaloric effects (MCEs) have been calculated. The entropy maximum change (-ΔS M) values are 7.40 J kg-1 K-1, 5.6 J kg-1 K-1 and 4.48 J kg-1 K-1, whereas the relative cooling power (RCP) values are 232 J kg-1, 230 J kg-1 and 156 J kg-1 for x = 0.00, 0.05 and 0.10, respectively, under an external field (µ 0 H) of 5 T. Through these results, the La0.6Ba0.2Sr0.2Mn1-x Ni x O3 (0 ≤ x ≤ 0.1) samples can be suggested for use in magnetic refrigeration technology above room temperature. The electrical resistivity (ρ) vs. temperature plots exhibit a transition from metallic behavior to semiconductor behavior in the vicinity of T M-SC. The adiabatic small polaron hopping (ASPH) model is applied in the PM-semiconducting part (T > T MS). Throughout the temperature range, ρ is adjusted by the percolation model. This model is based on the phase segregation of FM-metal clusters and PM-insulating regions.

Impact of synthesis route on structural, magnetic, magnetocaloric and critical behavior of Nd0.6Sr0.4MnO3 manganite.

Nd0.6Sr0.4MnO3 polycrystalline manganite was synthesized by two different methods: the auto-combustion reaction (NSMO-AC) and the sol-gel method (NSMO-SG). The structural, magnetic, magnetocaloric and critical behavior of the samples were examined. Rietveld refinements of the XRD patterns revealed that both compounds are pure single phase indexed to the orthorhombic system adopting the Pnma space group. The nanometric size estimated using the Williamson-Hall method was confirmed by TEM micrographs. Magnetic measurements as a function of temperature indicated that both samples underwent a second order ferromagnetic (FM)-paramagnetic (PM) phase transition at Curie temperature (T C). The relative cooling power was observed to be around 95.271 J kg-1 for NSMO-AC and 202.054 J kg-1 for NSMO-SG at µ 0 H = 5 T, indicating that these materials are potential candidates for magnetic refrigeration application close to room temperature. The critical behavior was estimated using diverse techniques based on the isothermal magnetization data recorded around the critical temperature T C. The calculated values are fully satisfactory to the requirements of the scaling theory, implying their reliability. The estimated critical exponents matched well with the values anticipated for the mean-field model and the 3D Ising model for NSMO-AC and NSMO-SG, respectively, showing that the magnetic interactions depended on the process of elaboration.

Structure, optical and magnetic properties of a novel homometallic coordination polymers: Experimental and Computational studies.

Single crystal of 1D homometallic coordination polymer involving cobalt metal ion and P2Mo5 Strandberg type polyoxometallate cluster (C6H10N2)2[Co(H2O)4P2Mo5O23].6H2O, is prepared in aqueous solution and characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance, fluorescence and magnetism. Single crystal X-ray diffraction analysis reveals that this compound crystallizes in the triclinic system with space group P [Formula: see text]. The 3-(ammoniomethyl)pyridine C6H8N2 organic fragment is used merely as stabilizer for the promotion of topological structure. DRS data indicate that the synthesized material can be identified as a ferromagnetic semiconductor with optical bands gaps energy of 1.81 and 2.74 eV, respectively. The large value of refractive index observed in the visible region make the simple a promising candidate for visible optical communication devices and fluorescent emisson result provides that the complex belongs to a blue luminescent compounds. Moreover, magnetic measurements and electronic structure calculations show that P2Mo5 Strandberg polyoxoanion can be reported as a new class of ligand that is candidate to construct metal-inorganic framworks with long distance ferromagnetic superechange between Co(II) centers. The evidence from this study suggests that the syntesized polymer can become a great multifunctional material openning the door for the developpement of new coordination polymers based on Strandberg type polyxoxmetalate with potential applications.

Long-range ferromagnetic order in perovskite manganite La0.67Ba0.25Ca0.08Mn(1-x)Ti x O3 (x = 0.00, 0.05 and 0.10).

In this study, we report the effects of Ti on the critical behavior of La0.67Ba0.25Ca0.08MnO3 samples prepared by the flux method. Moreover, the critical exponents ß, γ and δ are estimated through numerous techniques such as the modified Arrott plot, the Kouvel-Fisher method and critical isotherm analysis of the magnetic measurements on record near the Curie temperature. Compared to standard models, the estimated critical exponents are close to the theoretical values of the mean-field model for these samples. In order to estimate the spontaneous magnetization at a given temperature, we used a process based on the analysis, in the mean-field theory, of the magnetic entropy change (-ΔS M) vs. magnetization (M). An excellent agreement was found between the spontaneous magnetization determined from -ΔS M vs. M 2 and the classical extrapolation from the Arrott curves (µ 0 H/M vs. M 2), thus confirming that -ΔS M is a valid approach to estimate the spontaneous magnetization in this system. The accuracy of the critical exponent values was confirmed with the scaling hypothesis. The magnetization curves fall onto one of two sides, below and above T C.

Large magnetocaloric effect in manganese perovskite La0.67-x Bi x Ba0.33MnO3 near room temperature.

La0.67-x Bi x Ba0.33MnO3 (x = 0 and 0.05) ceramics were prepared via the sol-gel method. Structural, magnetic and magnetocaloric effects have been systematically studied. X-ray diffraction shows that all the compounds crystallize in the rhombohedral structure with the R3̄c space group. By analyzing the field and temperature dependence of magnetization, it is observed that both samples undergo a second order magnetic phase transition near T C. The value of T C decreases from 340 K to 306 K when increasing x from 0.00 to 0.05, respectively. The reported magnetic entropy change for both samples was considerably remarkable and equal to 5.8 J kg-1 K-1 for x = 0.00 and 7.3 J kg-1 K-1 for x = 0.05, respectively, for µ 0 H = 5 T, confirming that these materials are promising candidates for magnetic refrigeration applications. The mean-field theory was used to study the magnetocaloric effect within the thermodynamics of the model. Satisfactory agreement between experimental data and the mean-field theory has been found.

Critical behavior near room temperature in La0.75Ca0.05Na0.20MnO3 sample.

The critical behavior of La0.75Ca0.05Na0.20MnO3 was studied at around room temperature via magnetization measurements. From the relative slope, we deduced that the Tricritical Mean-Field model was the most suitable model. The estimated critical exponents were found to be ß = 0.24 ± 0.004, γ = 0.98 ± 0.065 and δ = 5.08 at T C = 300 K. These critical exponents satisfied the Widom scaling relation δ = 1 + γ/ß, implying the reliability of our values. Based on the critical exponents, the magnetization-field-temperature (M-µ 0 H-T) data around T C collapsed into two curves, obeying the single scaling equation with ε = (T - T C)/T C being the reduced temperature. These results suggest short-range interaction in our sample.

Anomalous behavior above the Curie temperature in (Nd1-x Gd x )0.55Sr0.45MnO3 (x = 0, 0.1, 0.3 and 0.5).

Magnetic properties were studied just above the ferromagnetic-paramagnetic (FM-PM) phase transition of (Nd1-x Gd x )0.55Sr0.45MnO3 with x = 0, 0.1, 0.3 and 0.5. The low-field inverse susceptibility (χ -1) of Nd0.55Sr0.45MnO3 exhibits a Curie-Weiss-PM behavior. For x ≥ 0.1, we observe a deviation in χ -1(T) behavior from the Curie-Weiss law. The anomalous behavior of the χ -1(T) was qualified as Griffiths phase (GP)-like. The study of the evolution of the GP through a susceptibility exponent, the GP temperature and the temperature range of the GP reveals that the origin of the GP is primary due to the accommodated strain. Likewise, the magnetic data reveal distinct features visible only for x = 0.5 at a low magnetic field that can be qualitatively understood as the result of ferromagnetic polarons, entailed by the strong effect of chemical/structural disorder, whose concentration increases upon cooling towards the Curie temperature. We explained the magnetic properties at a high temperature for the heavily Gd-doped sample (x = 0.5) within the phase-separation scenario as an assembly of ferromagnetic nanodomains, antiferromagnetically coupled by correlated Jahn-Teller polarons.

Pr3+ doping at the A-site of La0.67Ba0.33MnO3 nanocrystalline material: assessment of the relationship between structural and physical properties and Bean-Rodbell model simulation of disorder effects.

Bulk nanocrystalline samples of (La1-x Pr x )0.67Ba0.33MnO3 (0.075 ≤ x ≤ 0.30) manganites with a fixed carrier concentration are prepared by the sol-gel based Pechini method. Rietveld refinement of the X-ray diffraction patterns, shows the formation of single-phase compositions with rhombohedral symmetry. Upon Pr3+ doping at the A-site, the unit cell volume and the B-O-B bond angles are reduced. FTIR spectra present a prominent absorption peak of the in-phase stretching mode (B2g mode) rising from the vibration of the Mn-O bond. Raman spectra at room temperature reveal a gradual shift toward lower frequencies in (Eg) phonon mode with increasing Pr3+ concentration. The M(T) measurements shows a clear ferromagnetic (FM)-paramagnetic (PM) phase transition with increasing temperature. An increase in resistivity and activation energy and a decrease in the metal-semiconductor transition (T M-SC) and Curie temperatures (T C) was observed as a consequence of Pr3+ doping. The results are discussed according to the change of A-site-disorder effect caused by the systematic variations of the A-site average ionic radius 〈r A〉 and A-site-cation mismatch σ 2, resulting in the narrowing of the bandwidth and the decrease of the mobility of eg electrons. The magneto-transport behavior in the whole measured temperature and a magnetic field can be described by a percolation model, which is in agreement with the limited experimental data of the samples for x = 0.075, 0.15 and 0.30. The experimental results confirm that A-site substitution with Pr3+ destroys the Mn3+-O2--Mn4+ bridges and weakens the double exchange (DE) interaction between the Mn3+ (t3 2ge1 g, S = 2) and Mn4+ (t3 2ge0 g, S = 3/2) ions. On the other hand, the Bean and Rodbell model has been successfully used to simulate the magnetization data of the samples with x = 0.15 and x = 0.22. The random replacement of La3+ by Pr3+ is shown to induce more disorder in the system, which is reflected in the increase of the fitted disorder parameter and spin value fluctuation. At a temperature close to room temperature, the maximum magnetic entropy change (ΔS Max) and the relative cooling power (RCP) of La0.52Pr0.15Ba0.33MnO2.98 are found to be, respectively, 1.34 J kg-1 K-1 and 71 J kg-1 for a 1.5 T field change.

Large magnetocaloric entropy change at room temperature in soft ferromagnetic manganites.

In this paper, La0.75Ca0.25-x Na x MnO3 (x = 0.15 and 0.20) samples were prepared by the flux method. Crystallographic study revealed that the x = 0.15 sample is characterized by the coexistence of a mixture of orthorhombic and rhombohedral structures with Pbnm and R3̄c space groups, respectively. While, the x = 0.20 sample crystallized in the rhombohedral structure with a R3̄c space group. Magnetic data, under a magnetic field of 0.05 T, indicated that our samples undergo a ferromagnetic (FM)-paramagnetic (PM) phase transition, on increasing the temperature. The magnetic field dependence of the magnetocaloric properties of La0.75Ca0.25-x Na x MnO3 (x = 0.15 and 0.20) samples, with the second phase transition, was investigated. Near room temperature, the x = 0.20 sample exhibited a large magnetic entropy change with maxima of 6.01 and 3.12 J kg-1 K-1, respectively, under applied magnetic fields of 5 and 2 T. Also, the relative cooling power (RCP) was calculated. According to hysteresis cycles, for our studied samples, at 10 K a typical soft FM behavior with a low coercive field was observed. These results make our samples promising candidates for magnetic refrigerators, magnetic recording, and memory devices.

Copper-doped lanthanum manganite La0.65Ce0.05Sr0.3Mn1-x Cu x O3 influence on structural, magnetic and magnetocaloric effects.

Bulk nanocrystalline samples of La0.65Ce0.05Sr0.3Mn1-x Cu x O3 (0 ≤ x ≤ 0.15) manganites are prepared by the sol-gel based Pechini method. The effect of the substitution for Mn with Cu upon the structural and magnetic properties has been investigated by means of X-ray diffraction (XRD), Raman spectroscopy and dc magnetization measurements. The structural parameters obtained using Rietveld refinement of XRD data showed perovskite structures with rhombohedral (R3̄c) symmetry without any detectable impurity phase. Raman spectra at room temperature reveal a gradual change in phonon modes with increasing copper concentration. The analysis of the crystallographic data suggested a strong correlation between structure and magnetism, for instance a relationship between a distortion of the MnO6 octahedron and the reduction in the Curie temperature, T c. A paramagnetic to ferromagnetic phase transition at T C is observed. The experimental results confirm that Mn-site substitution with Cu destroys the Mn3+-O2--Mn4+ bridges and weakens the double exchange (DE) interaction between Mn3+ and Mn4+ ions, which shows an obvious suppression of the FM interaction in the La0.65Ce0.05Sr0.3Mn1-x Cu x O3 matrix. The maximum magnetic entropy change -ΔS max M is found to decrease with increasing Cu content from 4.43 J kg-1 K-1 for x = 0 to 3.03 J kg-1 K-1 for x = 0.15 upon a 5 T applied field change.

Analysis based on scaling relations of critical behaviour at PM-FM phase transition and universal curve of magnetocaloric effect in selected Ag-doped manganites.

The critical behaviour of Pr0.5Sr0.5-x Ag x MnO3 (0 ≤ x ≤ 0.2) samples around the paramagnetic-ferromagnetic phase transition is studied based on isothermal magnetization measurements. The assessments based on Banerjee's criteria reveal the samples undergoing a second-order magnetic phase transition. Various techniques such as modified Arrott plot, Kouvel-Fisher method, and critical isotherm analysis were used to determine the values of the ferromagnetic transition temperature T C, as well as the critical exponents of ß, γ and δ. The values of critical exponents, derived from the magnetization data using the Kouvel-Fisher method, are found to be (ß = 0.43 ± 0.002, 0.363 ± 0.068 and 0.328 ± 0.012), (γ = 1.296 ± 0.007, 1.33 ± 0.0054 and 1.236 ± 0.012) for x = 0.0, 0.1 and 0.2, respectively. This implies that the Pr0.5Sr0.5-x Ag x MnO3 with 0 ≤ x ≤ 0.2 systems does not belong to a single universality class and indicates that the presence of magnetic disorder in the system must be taken into account to fully describe the microscopic interaction of these manganites. With these values, magnetic-field dependences of magnetization at temperatures around T C can be well described following a single equation of state for our samples. From magnetic entropy change (ΔS M), it was possible to evaluate the critical exponents of the magnetic phase transitions. Their values are in good agreement with those obtained from the critical exponents using a modified Arrott plot (MAP). We used the scaling hypotheses to scale the magnetic entropy change and heat capacity changes to a universal curve respectively for Pr0.5Sr0.5-x Ag x MnO3 samples.

Critical phenomena and estimation of the spontaneous magnetization from a mean field analysis of the magnetic entropy change in La0.7Ca0.1Pb0.2Mn0.95Al0.025Sn0.025O3.

In the present work, we have studied the universal critical behavior in the perovskite-manganite compound La0.7Ca0.1Pb0.2Mn0.95Al0.025Sn0.025O3. Experimental results revealed that all samples exhibit a second-order magnetic phase transition. To study the critical behavior of the paramagnetic-ferromagnetic transition, various techniques such as modified Arrott plots, the Kouvel-Fisher method and critical isotherm analysis were used to determine the values of the Curie temperature T C, as well as the critical exponents ß (corresponding to the spontaneous magnetization), γ (corresponding to the initial susceptibility) and δ (corresponding to the critical magnetization isotherm). The critical exponent values for our sample are consistent with the prediction of the mean field model (ß = 0.46, γ = 1.0, and δ = 2.94 at an average T C = 302.12 K), indicating that the magnetic interactions are long-range. The reliability of the critical exponent values was confirmed by the Widom scaling relation (WSR) and the universal scaling hypothesis. Moreover, to estimate the spontaneous magnetization of La0.7Ca0.1Pb0.2Mn0.95Al0.025Sn0.025O3 perovskite, we used the magnetic entropy change (ΔS M), obtained from isothermal magnetization. The results obtained through this approach are compared to those obtained from classical analysis using Arrott curves. An excellent agreement is found between this approach and the one obtained from the extrapolation of the Arrott curves.

Magnetocaloric study, critical behavior and spontaneous magnetization estimation in La0.6Ca0.3Sr0.1MnO3 perovskite.

A detailed study of structural, magnetic and magnetocaloric properties of the polycrystalline manganite La0.6Ca0.3Sr0.1MnO3 is presented. The Rietveld refinement of X-ray diffraction pattern reveals that our sample is indexed in the orthorhombic structure with Pbnm space group. Magnetic measurements display a second order paramagnetic (PM)/ferromagnetic (FM) phase transition at Curie temperature T c = 304 K. The magnetic entropy change (ΔS M) is calculated using two different methods: Maxwell relations and Landau theory. An acceptable agreement between both data is noted, indicating the importance of magnetoelastic coupling and electron interaction in magnetocaloric effect (MCE) properties of La0.6Ca0.3Sr0.1MnO3. The maximum magnetic entropy change (-ΔS max M) and the relative cooling power (RCP) are found to be respectively 5.26 J kg-1 K-1 and 262.53 J kg-1 for µ 0 H = 5 T, making of this material a promising candidate for magnetic refrigeration application. The magnetic entropy curves are found to follow the universal law, confirming the existence of a second order PM/FM phase transition at T c which is in excellent agreement with that already deduced from Banerjee criterion. The critical exponents are extracted from the field dependence of the magnetic entropy change. Their values are close to the 3D-Ising class. Scaling laws are obeyed, implying their reliability. The spontaneous magnetization values determined using the magnetic entropy change (ΔS M vs. M 2) are in good agreement with those obtained from the classical extrapolation of Arrott curves (µ 0 H/M vs. M 2). The magnetic entropy change can be effectively used in studying the critical behavior and the spontaneous magnetization in manganites system.

Electrical conductivity and dielectric behaviour of nanocrystalline La0.6Gd0.1Sr0.3Mn0.75Si0.25O3.

An La0.6Gd0.1Sr0.3Mn0.75Si0.25O3 ceramic was prepared via a solution-based chemical technique. X-ray diffraction study confirms the formation of the compound in the orthorhombic structure with the Pnma group space. Dielectric properties have been investigated in the temperature range of 85-290 K with the frequency range 40 Hz to 2 MHz. The conductivity spectra have been investigated by the Jonscher universal power law: σ(ω) = σ dc + Aω n , where ω is the frequency of the ac field, and n is the exponent. The deduced exponent 'n' values prove that a hopping model is the dominating mechanism in the material. Based on dc-electrical resistivity study, the conduction process is found to be dominated by a thermally activated small polaron hopping (SPH) mechanism. Complex impedance analysis (CIA) indicates the presence of a relaxation phenomenon and allows us to modelize the sample in terms of an electrical equivalent circuit. Moreover, the impedance study confirms the contribution of grain boundaries to the electrical properties.

Large magnetic entropy change and prediction of magnetoresistance using a magnetic field in La0.5Sm0.1Sr0.4Mn0.975In0.025O3.

A detailed study of the structural, magnetic, magnetocaloric and electrical effect properties in polycrystalline manganite La0.5Sm0.1Sr0.4Mn0.975In0.025O3 is presented. The X-ray diffraction pattern is consistent with a rhombohedral structure with R3̄c space group. Experimental results revealed that our compound prepared via a sol-gel method exhibits a continuous (second-order) ferromagnetic (FM) to paramagnetic (PM) phase transition around the Curie temperature (T C = 300 K). In addition, the magnetic entropy change was found to reach 5.25 J kg-1 K-1 under an applied magnetic field of 5 T, corresponding to a relative cooling power (RCP) of 236 J kg-1. We have fitted the experimental data of resistivity using a typical numerical method (Gauss function). The simulation values such as maximum resistivity (ρ max) and metal-semiconductor transition temperature (T M-Sc), calculated from this function, showed a perfect agreement with the experimental data. The shifts of these parameters as a function of magnetic field for our sample have been interpreted. The obtained values of ß and γ, determined by analyzing the Arrott plots, are found to be T C = 298.66 ± 0.64 K, ß = 0.325 ± 0.001 and γ = 1.25 ± 0.01. The critical isotherm M (T C, µ 0 H) gives δ = 4.81 ± 0.01. These critical exponent values are found to be consistent and comparable to those predicted by the three-dimensional Ising model with short-range interaction. Thus, the Widom scaling law is fulfilled.

Structural, magnetic and magnetocaloric properties of 0.75La0.6Ca0.4MnO3/0.25La0.6Sr0.4MnO3 nanocomposite manganite.

The present study involves an investigation of structural, magnetic and magnetocaloric effect (MCE) properties of 0.75La0.6Ca0.4MnO3/0.25La0.6Sr0.4MnO3 composite material. Crystal structure analysis is performed by using Rietveld refinement of the X-ray diffraction patterns. The studied composite exhibits two structural phases; the rhombohedral and the orthorhombic structures corresponding to the mother compounds; La0.6Ca0.4MnO3 and La0.6Sr0.4MnO3, respectively. The scanning electron microscopy micrographs support our findings. Magnetic measurements as a function of temperature of the composite display two successive second order magnetic phase transitions at 255 and 365 K associated to both mother compounds. Therefore, a broadening of the magnetic entropy change peak is noted. A better relative cooling power (RCP) value of 360 J kg-1 compared to those observed in mother compounds is obtained at µ 0 H = 5 T, making of this material considered as a suitable candidate for magnetic refrigeration applications near room temperature. A consistent agreement between experimental results and numerical calculations based on the rule of mixtures has been shown. The theoretical modeling of the MCE using Landau theory reveals an acceptable concordance with experimental data indicating the importance of magnetoelastic coupling and electron interaction in the MCE properties of manganite systems. The field dependence of the magnetic entropy change is applied to study the critical behavior. Our results go in tandem with the values corresponding to the mean field model. The spontaneous magnetization values determined using the magnetic entropy change (ΔS M vs. M 2) are in good agreement with those found from the classical extrapolation of Arrott curves (µ 0 H/M vs. M 2).

Study of magnetic and electrical properties of Pr0.65Ca0.25Ba0.1MnO3 manganite.

The magnetic properties and magnetocaloric effect (MCE) in Pr0.65Ca0.25Ba0.1MnO3 have been investigated supplemented by electrical data. X-ray diffraction shows that the sample crystallizes in the distorted orthorhombic system with the Pnma space group. Pr0.65Ca0.25Ba0.1MnO3 undergoes paramagnetic-ferromagnetic (PM-FM) phase transition at T C ∼ 85 K. For a magnetic field change of 5 T, the maximum value of the magnetic entropy change (-ΔS max M) is estimated to be 4.4 J kg-1 K-1 around T C with a large relative cooling power (RCP) value of 263.5 J kg-1. While the modified Arrott plots suggested that the magnetic transition belongs to the second order phase transitions, the universal curves of the rescaled magnetic entropy (ΔS M) proved the opposite. The electrical properties of Pr0.65Ca0.25Ba0.1MnO3 have been investigated using impedance spectroscopy techniques. The dc-resistivity (σ dc) study shows the presence of semiconductor behavior. Ac-conductivity (σ ac) analysis shows that the conductivity is governed by a hopping process. From the analysis of the alternating regime, the exponent s variation obtained is in good agreement with Mott theory. The impedance spectrum analysis reveals the presence of a relaxation phenomenon. Based on these analyzes, the sample can be modeled by an electrical equivalent circuit.

Large reversible magnetocaloric effect in antiferromagnetic Ho2O3 powders.

Giant magnetocaloric materials are highly promising for technological applications in magnetic refrigeration. Although giant magnetocaloric effects were discovered in first-order magnetic transition materials, it is accompanied by some non-desirable drawbacks, such as important hysteretic phenomena, irreversibility of the effect, or poor mechanical stability, which limits their use in applications. Here, we report the discovery of a giant magnetocaloric effect in commercialized Ho2O3 oxide at low temperature (around 2 K) without hysteresis losses. Ho2O3 is found to exhibit a second-order antiferromagnetic transition with a Néel temperature of 2 K. At an applied magnetic field change of 5 T and below 3.5 K, the maximum value of magnetic entropy change [Formula: see text], the refrigerant capacity (RC) were found to be 31.9 J.K-1.kg-1 and 180 J.K-1, respectively.