Magnetocaloric Properties Of Pr0 Research Articles

Magnetic and magnetocaloric study of manganite compounds Pr0.5A0.05Sr0.45MnO3 (A=Na and K) and composite

Structural, magnetic and magnetocaloric properties of Pr0.5A0.05Sr0.45MnO3 (A=Na and K) have been investigated. Our samples have been elaborated by the conventional ceramic method at high temperature. X-ray diffraction patterns using Rietveld refinement reveal that our compounds are single phase and crystallize in the orthorhombic structure with Pbnm space group. Magnetization measurements versus temperature under an applied magnetic field of 50mT indicate that all our investigated samples exhibit a paramagnetic–ferromagnetic transition with decreasing temperature. The values of the Curie temperatures are 270K and 275K for A=Na and K, respectively. The magnetocaloric study of a manganite-based composite reveals an enhancement of relative cooling power which is around 67.37% of pure Gd under an applied magnetic field of 5T.

Magnetic and Magnetocaloric Properties of Pr0.8Bi0.2Fe x Mn1−x O3 Compounds with 0 ≤ x ≤ 0.3

This paper studies the effects of the Mn site substitution by Fe on the magnetic properties and the magnetocaloric properties of Pr0.8Bi0.2Fe x Mn1−x O3 elaborated by a sol–gel method. The variation of the magnetization as a function of temperature and applied magnetic field was carried out. Magnetic measurements show that all the materials exhibit a paramagnetic–ferromagnetic transition when the temperature decreases. The dependence of the Curie temperature (T C) and the magnetic entropy change (ΔS M) when varying the Fe doping content was investigated. The measured value of TC was 114, 97, 94, and 77 K for x = 0, 0.1, 0.2, and 0.3, respectively. The samples with x = 0 and x = 0.1 present a second-order phase transition, while the samples with x = 0.2 and x = 0.3 exhibit a first-order phase transition. As the concentration of Fe increases, the maximum entropy change, ${\Delta } S_{\mathrm {M}}^{\max }$ , decreases gradually, from 2.77 J kg−1 K−1 (x = 0) to 1.05 J kg−1 K−1 (x = 0.3), when the magnetic field changes from 0 to 5 T.

Structural, magnetic and magnetocaloric properties of K-doped Pr0.8Na0.2−xKxMnO3 manganites

In the present study we report the effect of A-site substitution by Potassium on the structural, magnetic and magnetocaloric properties in Pr0.8Na0.2−xKxMnO3 (0 ≤ x ≤ 0.15) samples synthesized using the solid state reaction at high temperatures. The Rietveld refinement of the X-ray powder diffraction shows that all our samples crystallize in the orthorhombic symmetry with Pbnm space group. The surface morphology of these samples was carried out using scanning electron microscopy (SEM). Magnetization measurements versus temperature in a magnetic applied field of 0.05 T indicate that K doping leads to a paramagnetic–ferromagnetic transition with a Curie temperature TC increasing from 117 K for x = 0.05 to 132 K for x = 0.15. The maximum of the magnetic entropy change |ΔSMMax| under a magnetic field of 5 T is found to be 3.20, 3.44, 3.32, and 3.30 Jkg−1 K−1 for x = 0, 0.05, 0.1 and 0.15, respectively. Large relative cooling power (RCP) value of 355.6 Jkg−1 is obtained for Pr0.8Na0.2MnO3 compound, at a field change of 5 T. This relatively large value associated to a Curie temperature of 90 K make the present compound a promising candidate for magnetic refrigeration at low temperatures.

The effect of Co doping on the magnetic and magnetocaloric properties of Pr0.7Ca0.3Mn1−xCoxO3 manganites

In this work, we report the effect of low amount of cobalt doping at the Mn-site on the magnetic and magnetocaloric properties of Pr0.7Ca0.3Mn1−xCoxO3 (0≤x≤0.1) powder samples. Our samples, elaborated using the solid–solid reaction method at high temperature, are single phase and crystallize in the orthorhombic system with Pnma space group. While the parent compound Pr0.7Ca0.3MnO3 exhibits a charge order state at low temperature, the substituted samples with low amount of cobalt exhibit a paramagnetic to ferromagnetic transition with decreasing temperature. The Curie temperature TC increases with Co content from 105K for x=0 to 116K for x=0.1. The maximum values of the magnetic entropy change |ΔSMmax| are found to be 0.8J/kgK, 2.2J/kgK, 3.1J/kgK and 3.2J/kgK in a magnetic field change of 5T for x=0, 0.02, 0.05 and 0.1 respectively. The maximum value of the relative cooling power RCP is found to be 378.2J/kg in the Pr0.7Ca0.3Mn0.95Co0.05O3 at 5T. This value of RCP is about 92% of that obtained in gadolinium metal, known as one of the most important materials for magnetic refrigeration, at the same magnetic field change of 5T.

Impact of sintering temperature on the magnetic and magnetocaloric properties in Pr0.5Eu0.1Sr0.4MnO3 manganites

This article covers the detailed study on the magnetic and magnetocaloric properties of Pr0.5Eu0.1Sr0.4MnO3 samples. The materials were synthesized through the sol–gel using nitrate–citrate route method by sintering at four different temperatures starting from 600 to 1000°C. Phase purity, structure, size, and crystallinity were investigated using XRD and SEM. The structure, magnetic properties and magnetocaloric effect of Pr0.5Eu0.1Sr0.4MnO3 ceramics with different particle sizes have been investigated. Regardless of the sintering temperature, the orthorhombic crystal structure with the Pnma space group is stable. XRD analysis showed that the particle size increases with the increase in sintering temperature. The Curie temperature shifted from 90K to 270K. Magnetization, magnetic entropy change (ΔS), and relative cooling power (RCP) also increased with size in the nanocrystalline samples. The magnetic entropy changes were about 0.89J/kgK, 2.75J/kgK, 3.34J/kgK, and 3.82J/kgK for the samples sintered at 600°C, 800°C, 900°C and 1000°C, respectively when a magnetic field of 5T was applied. It is shown that for Pr0.5Eu0.1Sr0.4MnO3 the magnetic entropy change follows a master curve behavior.

Effects of partial Mn-substitution on magnetic and magnetocaloric properties in Pr0.7Ca0.3Mn0.95X0.05O3 (Cr, Ni, Co and Fe) manganites

Structural, magnetic and magnetocaloric properties of Pr0.7Ca0.3Mn0.95X0.05O3(X=Cr, Ni, Co and Fe) ceramics have been investigated by X-ray diffraction (XRD) and magnetic measurements. Powder samples have been elaborated using thesolid state reaction method at high temperature. The Rietveld analysis of the powder X-ray diffraction shows that the samples crystallize in the orthorhombic structure with Pnma space group. Magnetic measurements show that all our materials exhibit a paramagnetic–ferromagnetic transition with decreasing temperature. The Arrott plots of ours materials reveal the occurrence of a second-order phase transition. The maximum values of magnetic entropy change |ΔSMmax| are 2.92, 2.96, 3.1, and 2.38Jkg−1K−1 and the relative cooling power (RCP) values are 405.8, 378.2, 352.2 and 337.4Jkg−1 for a magnetic-field change from 0 to 5T for Cr, Ni, Co and Fe respectively. The large RCP found in our substituted samples will be interesting for magnetic refrigeration over a wide temperature range ∼130K around its paramagnetic to ferromagnetic transition temperature. With the scaling laws of ΔSM, the experimental ΔSM collapse onto a universal curve for several ceramics, where an average curve is obtained. With the phenomenological universal curve, the experimental ΔSM are well predicted for all materials.

Effect of hydrostatic pressure on magnetic and magnetocaloric properties of Mn-site doped perovskite manganites Pr0.6Ca0.4Mn0.96B0.04O3 (B=Co and Cr)

We have investigated the effect of hydrostatic pressure on magnetization and magnetocaloric properties of Pr0.6Ca0.4Mn0.96B0.04O3 (B = Co and Cr) polycrystals. At ambient pressure, both the systems undergo a first-order paramagnetic insulator to ferromagnetic metallic transition. On increasing the hydrostatic pressure, the ferromagnetic Curie temperature (TC) shifts towards high temperature at a rate of dTC/dP = 34 K/GPa (23.15 K/GPa) and 31.1 K/GPa (20.7 K/GPa) during cooling (warming) for B = Co and Cr, respectively. While the hysteresis in magnetization decreases with increasing pressure, P = 1 GPa is insufficient to completely suppress the first order transition. The magnetic entropy change (ΔSM) was calculated for various pressures up to 1 GPa and under a magnetic field of μ0H = 1-5 T. The application of pressure, as well as the magnetic field, shifts the peak in ΔSM(T) towards a higher temperature. The maximum value of ΔSM (ΔSMmax) is increased by the magnetic field but decreased by the pressure. It is also observed that while the magnetic field increases the Relative Cooling Power (RCP) of both samples, pressure decreases the RCP of Co doped but does not affect the RCP of Cr doped sample.

Effect of Fe Substitution on the Structural, Magnetic and Magnetocaloric Properties of Pr0.6La0.1Mg0.3Mn1−x Fe x O3 (0≤x≤0.3) Perovskite Manganites Prepared by Sol Gel Method

Studies of the structural, magnetic, and magnetocaloric properties of polycrystalline Pr0.6La0.1Mg0.3Mn1−x Fe x O3 (0≤x≤0.3) perovskite manganites were carried out. The compounds were synthesized using the sol–gel method. X-Ray diffraction (XRD) analysis using Rietveld refinement shows that all our compounds crystallize in the orthorhombic structure with the Pnma space group. The surface morphology and elemental analysis of both samples were carried out by scanning electron microscopy (SEM) and the energy dispersive X-ray technique (EDX), respectively. Magnetization measurements versus temperature under magnetic applied field of 0.05 T showed that all our investigated samples display a ferromagnetic-paramagnetic transition. The substitution of Mn by Fe leads to an increase of the Curie temperature T C from 64 K for x=0 to 380 K for x=0.3. The Arrott plots show that the phase transition is of second order. A large magnetic entropy change |ΔS M | deduced from isothermal magnetization curves has been recorded in the parent compound Pr0.6La0.1Mg0.3MnO3 reaching a maximum of 0.79 J/kg K under a magnetic applied field of 2 T close to T C . Our results on magnetocaloric properties suggest that the Pr0.6La0.1Mg0.3MnO3 compound is attractive as a possible refrigerant for low temperature magnetic refrigeration.

Morphology, Structural, Magnetic, and Magnetocaloric Properties of Pr0.7Ca0.3MnO3 Nanopowder Prepared by Mechanical Ball Milling Method

A sample of Pr0.7Ca0.3MnO3 nanopowder was prepared by the ball milling method. The crystal structure examined by X-ray powder diffraction indicates that the sample is single phase and crystallizes in the orthorhombic perovskite system with Pnma space group at room temperature. The average crystallite size of 29 nm was obtained by X-ray diffraction. Magnetic measurements showed that the sample exhibits a ferromagnetic-to-paramagnetic transition at a Curie temperature close to 120 K. The magnetic entropy change |ΔS M | has been deduced by the Maxwell relation method. The maximum value of the magnetic entropy change $\vert \Delta {S}_{M}^{\max} \vert$ obtained from the M(H) plot data is found to be 0.86 J/kg K for an applied magnetic field of 2 T. At this value of magnetic field the relative cooling power (RCP) is 44.05 J/kg. At low temperature, large change in magnetic entropy has been observed in the sample. Our result on magnetocaloric properties suggests that Pr0.7Ca0.3MnO3 nanopowder is attractive as a possible refrigerant for low-temperature magnetic refrigeration.

Effect of Ce doping on the magnetic and magnetocaloric properties of Pr0.5Sr0.5−xCexMnO3 manganites

The magnetic and magnetocaloric effects of manganites of Pr0.5Sr0.5−xCexMnO3 (x = 0, 0.04, 0.08 and 0.1) prepared by standard solid-state reaction method are investigated. Large magnetic entropy changes (ΔSm) with the ferromagnetic–paramagnetic transition have been found. The ΔSm and Curie temperature (TC) gradually increase with increasing Ce content. The maximum of magnetic entropy change in a low magnetic change of 15 kOe is about −1.93 J kg−1 K−1 for x = 0.1 sample with a TC value of 310 K. Due to the large ΔSm and tunable TC around the room temperature, it is suggested that Pr0.5Sr0.5−xCexMnO3 could be used as desirable active room temperature magnetic refrigerants.

Reversibility in the adiabatic temperature-change of Pr0.73Pb0.27MnO3

The investigation of structure, magnetic and magnetocaloric properties of Pr0.73Pb0.27MnO3 perovskite has been studied by using the X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and magnetization. The X-ray diffraction pattern shows reflections typical of the perovskite structure with cubic symmetry. The field cooled (FC), zero-field-cooled (ZFC) and field-heated (FH) thermomagnetic measurements at 50Oe indicate a sharp change of magnetization at the phase-transition (TC≈234K). The magnetic entropy changes were determined from M(H) isotherms that were measured at various temperatures around TC. The magnetic entropy changes in magnetic field changes of 1T and 2T were 2.4Jkg−1K−1 and 3.8Jkg−1K−1, respectively. The adiabatic temperature change of this material, ΔTad, was measured by means of an adiabatic calorimeter directly. The results indicate a maximum adiabatic temperature change produced by a magnetic field change of 3T is 2.5K at 236K.

Effect of Li doping on the magnetic and magnetocaloric properties of Pr0.5Sr0.5−xLixMnO3 (0≤x≤0.3)

The magnetic properties and magnetocaloric effect have been studied in Pr0.5Sr0.5−xLixMnO3 (0≤x≤0.3) prepared by conventional solid-state reaction. Magnetic measurements versus temperature revealed that the Curie temperature (TC) increased gradually with increasing lithium content (0.05≤x≤0.2); TC values are about 260 and 290K for x=0.05 and 0.2, respectively. But it shows abrupt drop in TC value for x=0.3 (TC=235K). Meanwhile, the paramagnetic–ferromagnetic (PM–FM) transition is second-order in x≤0.2, it changes into first order for x=0.3. However, the magnitude of the isothermal magnetic entropy (ΔSM) increased gradually. In a magnetic field change of 15.0kOe, the maximum ΔSM achieved around TC are −1.03, −1.05, −1.48, −2.17 and −2.64Jkg−1K−1 for x=0, 0.05, 0.1, 0.2and 0.3, respectively. Although ΔSM for x=0.2 is smaller compared to the composition x=0.3, the relative cooling capacity (RCP) 59.6Jkg−1 is similar compared with the value 59.8Jkg−1 for x=0.3. Addition of suitable TC makes it a desirable material for room temperature magnetic refrigeration.

Magnetocaloric Effects in Pr0.6−x Er x Sr0.4MnO3 (0.0≤x≤0.2) Manganese Oxides

The effects of partial substitution of praseodymium by erbium on the structural, magnetic, and magnetocaloric properties of Pr0.6−x Er x Sr0.4MnO3 (0.0≤x≤0.2) powder samples have been studied. Our polycrystalline compounds were synthesized by the conventional solid state reaction at high temperature. Rietveld refinement of the X-ray diffraction patterns using Fullprof program shows that all our samples are single phase and crystallize in the orthorhombic structure with the Pnma space group. The unit cell volume decreased with increasing the Er amount. Magnetic measurements show that all our samples exhibit a paramagnetic–ferromagnetic transition with decreasing temperature. The Curie temperature T C shifts to lower values with increasing Er content. From the magnetization isotherms at different temperatures, magnetic entropy changes ΔS M and relative cooling power RCP have been evaluated. The maximum of the magnetic entropy changes for the Pr0.45Er0.15Sr0.4MnO3 sample is found to be $| \Delta S_{M}^{\max } | = 2.66~\mathrm{J}\,\mathrm{kg}^{-1}\,\mathrm{K}^{-1}$ under a magnetic applied field change of 2 T.

Composition Dependence of Magnetocaloric Effect in Pr<SUB>0.6</SUB>Ca<SUB>0.4</SUB>Mn<SUB>1−<I>x</I></SUB>Cr<SUB><I>x</I></SUB>O<SUB>3</SUB> (<I>x</I> = 0.02–0.08)

We report the effect of varying Cr content on magnetic and magnetocaloric properties of Pr0.6Ca0.4Mn(1-x)Cr(x)O3 samples (x = 0, 0.02, 0.04, 0.06 and 0.08). While the parent compound (x = 0) is a charge ordered and antiferromagnetic insulator, Cr doped compounds are ferromagnetic metals with nearly same Curie temperature (T(c) approximately 140 K). We find unusual field-induced meta-magnetic transition above T(c) in x = 0.02 and 0.04 which is absent in x = 0.06 and 0.08. It is suggested that the paramagnetic phase in these compounds is inhomogeneous with coexistence of nano-size ferromagnetic clusters and short range charge ordered clusters. Field induced growth of ferromagnetic nano-clusters and destruction of short-range charge ordering leads to the observed metamagnetic transition, which results in large magnetic entropy change of -deltaS(M) = 5.043, 6, 5.509 and 4.375 J/kg K under deltaH = 5 T, for x = 0.02, 0.04, 0.06 and 0.08, respectively. In addition, large relative cooling power (RCP) found in these materials (327.384, 286.36, 272.22 and 279.936 J/kg) makes it interesting for practical applications. Our study suggests that creation of ferromagnetic nano-clusters in the paramagnetic phase by Mn-site doping in charge ordered compounds provides an alternative approach to achieve high AS(M) and RCP values.

ChemInform Abstract: The Effect of Strontium Deficiency in Pr0.6Sr0.4MnO3 Perovskite Manganites.

AbstractThe structural, magnetic, and magnetocaloric properties of Pr0.6Sr0.4‐δMnO3 (0 ≤ δ ≤ 0.2) are characterized by powder XRD and magnetic measurements.

Structural, magnetic, electrical and magnetocaloric properties in Pr0.6Sr0.4MnO3/BaTiO3composites

Structural, magnetic, electrical and magnetocaloric properties in Pr_0.6Sr_0.4MnO₃/BaTiO₃composites