Magnetocaloric Properties Of Pr0 Research Articles

Finite-size effects on the evolution of magnetic correlations and magnetocaloric properties of Pr0.4Bi0.2Sr0.4MnO3

The effect of particle size reduction on the magnetic correlations of Pr0.4Bi0.2Sr0.4MnO3 nanoparticles prepared by top-down approach has been studied in detail. It was observed that as the milling time increases from 0 to 240 min, particle size decreases from 160 to 12 nm. Correspondingly it was observed that the ferromagnetic transition temperature (TC) drops (264 to 213 K) and saturation magnetization (MS) decreases (2.12–0.41 {upmu }_{mathrm{B}}/mathrm{f}.mathrm{u}.) while coercivity (HC) shows a monotonous increase (0.18–1.5 kOe) as the particle size decreases due to increase in milling. The magnetic entropy change (ΔS) also decreases (2.41–0.24 J/kg-K) as particle size decreases indicating a strong correlation between magnetism and particle size. The metamagnetic M–H response of the bulk sample, which signifies the magnetic phase coexistence, is suppressed, and the nature of magnetic interactions demonstrates a transition from long range to short range. The observed characteristics emphasizes that with particle size reduction there is an increase in the surface disorder which can be explained by considering the core–shell model for the nanoparticles.Graphic abstract

Tuning magnetic and magnetocaloric properties of Pr0.6Sr0.4MnO3 through size modifications

Particle size as an effective tool for controlling the magnetic and magnetocaloric properties of Pr0.6Sr0.4MnO3 samples has been studied. In the present work, a direct influence of particle size on the magnitude of magnetization and magnetic transition temperature, TC, can be seen. The TC drops from 309 to 242 K, while the saturation magnetization (MS) decreases from 3.6 to 0.5 μB/f.u. as the particle changes from 120 to 9 nm. Concurrently, coercivity (HC) exhibits a drastic rise emphasizing the enhanced surface disorder in the nanoparticles. Another interesting observation is in the magnetic entropy change, ΔS, which though decreases in magnitude from 5.51 to 3.90 J/Kg-K as particle size decreases from 120 to 30 nm, but the temperature range of ΔS (i.e., relative cooling power, RCP) increases from 184.33 to 228.85 J/Kg. Such interplay between magnitude and wider temperature range of ΔS, which can be fine-tuned by particle size, provides an interesting tool for using surface spin disorder, as a control mechanism in modifying physical properties.

Structure, magnetic and magnetocaloric properties of Pr0.5Sr0.5MnO3 with cobalt substitution

Structure, magnetic and magnetocaloric properties of Pr0.5Sr0.5MnO3 with cobalt substitution

The effect of Ni-substitution with Mn on electrical, magnetic and magnetocaloric properties in Pr0.67Ba0.22Sr0.11Mn1−xNixO3 manganites

The effect of Ni-substitution with Mn on electrical, magnetic and magnetocaloric properties in Pr0.67Ba0.22Sr0.11Mn1−xNixO3 manganites

Effects of Ru substitution on the structural, magnetic and magnetocaloric properties of Pr0.68Ca0.22Sr0.1Mn1−xRuxO3 (x = 0, 0.05, 0.1 and 0.2) compounds

The structural, magnetic and magnetocaloric properties of polycrystalline Pr0.68Ca0.22Sr0.1Mn1−xRuxO3 (x = 0, 0.05, 0.1 and 0.2) compounds were studied. All the samples crystallized in an orthorhombic symmetry. A significant increase in the lattice parameters in the doped samples was attributed to the existence of Ru with a the mixed-valence state (Ru3+/Ru4+). The increase in the Curie temperature (Tc) with increasing Ru content was interpreted as Ru doping promoting the ferromagnetic interactions between Ru4+–Mn3+ and Ru4+–Mn4+pairs. The decrease in saturation magnetisation was attributed to an AFM interaction between the Ru3+–Mn3+ and Ru3+–Mn4+ pairs and smaller magnetic moments of Ru than those of Mn. The decrease in |ΔSM| (from 4.66 J kg−1 K−1 for x = 0.05 to 2.32 J kg−1 K−1 for x = 0.2 at 5 T) was attributed to the nature of phase transition (from a first-order to second-order transition) and a decrease in the saturation magnetisation.

Sintering temperature effect on the magnetic properties of Pr0.67Sr0.33MnO3 manganite

This paper covers a detailed study of the structural, morphological, magnetic, and magnetocaloric properties of Pr0.67Sr0.33MnO3 compound prepared via sol–gel method with different sintering temperatures (700 °C ≤ TS ≤ 1200 °C). The structural study revealed that all samples crystallize in the orthorhombic structure with Pnma space group, with the presence of some impurities for TS ≤ 850 °C. With increasing sintering temperature TS, the Curie temperature shifts from 256 to 290 K. The evolution of the magnetic properties may be explained in terms of the core–shell model. The disordered magnetic behavior induces a spin-glass-like state at low temperature with the presence of Griffiths phase above Curie temperature. Magnetocaloric study indicated a relative cooling power of 97.78 J/kg under 2 T magnetic field at room temperature for the sample sintered at 1000 °C, indicating that this sample is a suitable candidate for magnetic refrigeration.

Magnetic and Table-Like Magnetocaloric Properties of Polycrystalline Pr0.7Ba0.1Sr0.2MnO3

The magnetic and magnetocaloric properties of Pr0.7Ba0.1Sr0.2MnO3 polycrystalline are presented. The sample is single phase of a monoclinic structure with a = 5.4726 A, b = 5.5045 A, c = 7.7339 A, α = γ = 90°, and β = 90.003°. X-ray absorption spectrum shows a co-existence of Mn4+ and Mn3+ ions in the compound. A ferromagnetic–paramagnetic (FM–PM) phase transition occurs at around 232 K. An analysis of the critical behavior near the FM–PM transition indicates a short-range magnetic ordering in Pr0.7Ba0.1Sr0.2MnO3 with critical exponents dependent on an applied magnetic field. The critical parameters are found to be β = 0.220 ± 0.03, 0.224 ± 0.002, and 0.227 ± 0.002, γ = 0.732 ± 0.011, 0.818 ± 0.003, and 0.958 ± 0.013, TC = 232.7, 234.6, and 236.6 K for field ranges of 1–3 T, 3–4 T and 4–5 T, respectively. The maximum entropy change (− ΔSmax) is found to be 5.67 J/kg K near the TC for a 5 T of field change. The table-like magnetocaloric effect observed in this sample is desirable for active magnetic refrigeration.

Magnetic and Magnetocaloric Properties of K-Doped Pr0.5Sr0.5MnO3

We have studied the effect of potassium substitution on the magnetic and magnetocaloric properties of Pr0.5Sr0.5−xKxMnO3 (x = 0, 0.05, 0.1, 0.15, 0.2, and 0.3). X-ray diffraction results show an orthorhombic crystal structure formed at room temperature for x ≤ 0.2. The maximum entropy change (|ΔSM|max) of the samples gradually increases from 1.15 (x = 0) to 3.37 J kg−1 K−1 (x = 0.3) in a magnetic field change of 15 kOe with increasing concentration of potassium. The Curie temperatures (TC) are found to be 265, 285, 295, 300, 295, and 220 K for x = 0, 0.05, 0.1, 0.15, 0.2, and 0.3, respectively. The temperature range of the phase transition becomes wider, the relative cooling power (RCP) gradually increases with the content of potassium, and the largest RCP is achieved to be 63.5 J kg−1 for x = 0.3, which makes it as a desirable material for the room temperature magnetic refrigeration.

Bi doping effect on the critical behavior and magnetocaloric effect of Pr0.8−xBixSr0.2 MnO3 (x = 0, 0.05 and 0.1)

In this study, we report the effect of Bi doping on the critical behavior and the magnetocaloric properties of Pr0.8−xBixSr0.2MnO3 (x = 0, 0.05 and 0.1) structures prepared by sol-gel method. Refined values of the critical exponents β, γ, and δ determined from the modified Arrott plots and Kouvel–Fisher method show that the parent sample is described by the tricritical mean field model whereas the 3D-Ising model is the best model describing doped samples. Consequently, a transition from long-range to short range FM interactions caused by the introduction of Bi in the parent sample can be identified. All samples reveal the presence of some ferromagnetic domains in the paramagnetic phase. In the vicinity of the Curie temperature TC and for an applied magnetic field of 5 T, the maximum of magnetic entropy change |ΔSM| decreases from 5.41 J K−1kg−1 for x = 0–3.11 J K−1kg−1 for x = 0.1, respectively. The |ΔSM| for doped samples exhibits a large broad variation with temperature around TC as compared with the parent sample. Such effect is substantially advantageous for magnetic refrigeration. Also, the magnetocaloric effect is investigated using Landau theory. A good agreement is obtained between this theory and experimental data, which suggests that electronic interactions and magnetoelastic coupling are at the origin of the magnetocaloric properties of our samples. In addition, we report that |ΔSM| curves follow the universal law confirming the second-ordered paramagnetic-ferromagnetic transition.

Effect of Ag substitution on structural, magnetic and magnetocaloric properties of Pr0.6Sr0.4–xAgxMnO3 manganites

A systematic investigation on the structural, magnetic and magnetocaloric properties of Pr0.6Sr0.4–xAgxMnO3 (x=0.05 and 0.1) manganites was reported. Rietveld refinements of the X-ray diffraction patterns confirmed that all samples were single phase and crystallized in the orthorhombic structure with Pnma space group. Magnetic measurements in a magnetic applied field of 0.01 T revealed that the ferromagnetic-paramagnetic transition temperature TC decreased from about 293 to 290 K with increasing silver content from x=0.05 to 0.1. The reported magnetocaloric entropy change and relative cooling power for both samples were considerably remarkable with a ΔSmax value of 1.9 J/(kg·K) and maximum RCP values of 100 J/kg, under a magnetic field change (Δµ0H) equal to 1.8 T. The analysis of the universal curves gave an evidence of a second order magnetic transition for the studied samples. The magnetic field influence on both the magnetic entropy change and the relative cooling power was also studied and discussed.

Structural characterization and magnetic field dependence of the magnetocaloric properties in Pr0.8Na0.05K0.15MnO3 ceramic

Pr0.8Na0.05K0.15MnO3 sample was prepared by solid-state reaction method. Refinement of the X-ray diffraction patterns shows that the sample is single phase and crystallizes in the orthorhombic structure with Pbnm space group. This result was confirmed by using the electron diffraction pattern for the sample using the [001] orientation. Analyzing temperature and field dependences of magnetization around the ferromagnetic-paramagnetic transition reveals the sample undergoing the second-order magnetic phase transition. The isothermal entropy changes ΔS as a function of temperature in different magnetic fields were determined. A phenomenological model is used to calculate magnetic and magnetocaloric properties of Pr0.8Na0.05K0.15MnO3 compound. The maximum values of ΔSmax and the relative cooling power (RCP) increase with increasing applied magnetic field. Landau theory and phenomenological universal curves of entropy change confirm the second order phase transition.

Field dependence of magnetocaloric properties of 20% Cr-doped Pr0.7Ca0.3MnO3 perovskite

In this study, we have investigated the effect of 20% Cr doping at the Mn site on the magnetic and magnetocaloric properties of Pr0.7Ca0.3MnO3 polycrystalline manganites elaborated using the solid-state reaction. The X-ray powder diffraction shows that compounds crystallize in the orthorhombic system with Pnma space group. The parent compound Pr0.7Ca0.3MnO3 is a well-known charge-ordered (CO) compound. The selective substitution of Cr for Mn in the pristine compound destroys the CO ordering observed in Pr0.7Ca0.3MnO3, and a paramagnetic to ferromagnetic transition takes place. The field dependence of the magnetic entropy change ∆S and of the relative cooling power RCP is reported. The \(\left| {\Delta S^{\hbox{max} } } \right|\) are found to be 0.8 and 2.87 J kg−1 K in a magnetic field change of 5 T for x = 0 and 0.2, respectively. The RCP is found to be 253.2 J kg−1 in the Pr0.7Ca0.3Mn0.8Cr0.2O3 at 5 T. With the scaling laws, the experimental ∆S and n collapse onto a universal curve for Pr0.7Ca0.3Mn0.8Cr0.2O3 sample, where an average curve is obtained for ∆S. With the phenomenological universal curve, the magnetic entropy change ∆S curves are well predicted for Cr-substituted sample. Additionally, Banerjee’s criteria, the universal behavior and Landau theory of phase transitions were also studied to assess magnetic ordering in the Pr0.7Ca0.3Mn0.8Cr0.2O3 material.

Effect of Monovalent Cation Doping on Structural, Magnetic, and Magnetocaloric Properties of Pr0.85 A 0.15MnO3 (A = Ag and K) Manganites

A systematic study on the effect of monovalent cation doping on structural, magnetic, and magnetocaloric properties of Pr0.85 A 0.15MnO3 (A = Ag and K) samples synthesized by a sol-gel method has been carried out. The crystal structure and morphology have been worked by X-ray diffraction (XRD) and scanning electron microscopy (SEM) imaging measurements. The XRD results indicate that both samples have orthorhombic structure. Magnetization versus temperature measurements show that our samples display a ferromagnetic-to-paramagnetic phase transition with increasing temperature. The ferromagnetic-to-paramagnetic phase transition temperature (T C) values were found as 74 and 116 K for Pr0.85Ag0.15MnO3 and Pr0.85 K 0.15MnO3, respectively. The magnetic entropy changes were evaluated from isothermal magnetization curves measured at various temperatures near T C by steps of 4 K. The values of the magnetic entropy change were determined as 0.99 and 1.39 J kg −1 K −1 for Pr0.85Ag0.15MnO3 and Pr0.85 K 0.15MnO3 under external field changes of 10 kOe, respectively.

A Comparative Study of the Structural, Magnetic and Magnetocaloric Properties in Pr0.6La0.1M0.3MnO3 Manganites (M = Ca, Ba and Mg)

A Comparative Study of the Structural, Magnetic and Magnetocaloric Properties in Pr0.6La0.1M0.3MnO3 Manganites (M = Ca, Ba and Mg)

Effects of synthesis route on the structural, magnetic and magnetocaloric properties of Pr0.8K0.2MnO3

Pr0.8K0.2MnO3 ceramics are prepared by solid-state reaction and Pechini sol–gel method. The influence of the powder synthesis method on the structural, morphological, magnetic and magnetocaloric properties of the samples are investigated. The X-ray diffraction pattern shows reflections typical of the perovskite structure with orthorhombic symmetry. The experimental results reveal that both samples undergo a second-order phase transition. The maximum magnetic entropy changes, deduced from the M–µ0H measurements, are 3.77 and 7.23J/kgK under the magnetic field change of 5T for Pr0.8K0.2MnO3 synthesized by using solid-state reaction and sol–gel methods respectively. The field dependence of magnetic entropy change is analyzed showing the power law dependence, ΔS(T,µ0H)=a(T)(μ0H)n(T,H) at the Curie temperature. Using the scaling laws of ∆S, the experimental ∆S collapse onto a universal curve for both ceramics. These results suggest that the physical properties of our samples are strongly depended on synthesis techniques. It is found that Pechini sol–gel method is more efficient and stable to obtain ceramic materials with good magnetic properties. Consequently, a substantial increase of the ferromagnetic to paramagnetic transition temperature and an enhancement of magnetocaloric properties are observed in the sol-gel made sample making it more suitable for magnetic refrigeration applications.

Electrical conductivity analysis and magnetic properties of Pr0.7Ca0.3Mn0.95Co0.05O3 oxide

The structural, electrical, magnetic and magnetocaloric properties of Pr0.7Ca0.3Mn0.95Co0.05O3 have been studied. The X-ray diffraction refinement results indicate that the sample is single phase and crystallizes in the distorted orthorhombic system with Pnma space group. The investigation of the temperature and frequency dependence of conductance indicates that the sample exhibits a semi-insulator character and the conduction mechanism is explained using hopping model. Complex impedance analysis confirms the contribution of grain boundary in the transport properties in the Pr0.7Ca0.3Mn0.95Co0.05O3 system. Magnetocaloric effect and transition order are investigated by using magnetization measurements. The field dependence of magnetic entropy change and relative cooling power are analyzed and showing the power law dependence. The Landau theory for phase transitions framework is applied to describe the magnetocaloric effect in Pr0.7Ca0.3Mn0.95Co0.05O3 manganite. The obtained results are discussed in terms of magnetoelastic and electron interaction contribution to the magnetic entropy.

Structural, magnetic and magnetocaloric investigations in Pr0.6−xErxCa0.1Sr0.3MnO3 (0 ≤ x ≤ 0.06) manganites

We studied the structural, magnetic and magnetocaloric properties of Pr0.6−xErxCa0.1Sr0.3MnO3 (0 ≤ x ≤ 0.06) perovskite manganites. The samples were synthesized using the solid-state reaction at high temperature and were analyzed by X-ray diffraction and magnetic measurements. X-ray diffraction analysis shows that all compounds were found to be single phase and crystallize in the orthorhombic structure with Pnma space group. Magnetization measurements show that all compounds exhibit a paramagnetic to ferromagnetic transition with decreasing temperature. The Curie temperature TC decreases with increasing erbium content from 275 K for x = 0–220 K for x = 0.06. From the M (H) curves, the maximum of the magnetic entropy change |ΔSMmax| under a magnetic field change of 5T was found to be 4.35 J kg−1 K−1 for x = 0.04 which corresponds to a relative cooling power (RCP) about 321 J/kg under the same applied magnetic field. The sensitivity of magnetic entropy change to magnetic field is estimated by the local exponent n (T, μ0H) which determines the field dependence of the experimental |ΔSM|. Moreover, rescaled entropy data for all samples collapses into the same universal curve, revealing universal behavior for the magnetocaloric effect in these compounds.

Effect of trivalent rare earth doping on magnetic and magnetocaloric properties of Pr0.5(Ce,Eu,Y)0.1Sr0.4MnO3 manganites

Experimental studies of the structural, magnetic and magnetocaloric properties of the three compounds Pr0.5X0.1Sr0.4MnO3 (X = Ce, Eu and Y) are reported. Our samples were synthesized using the Pechini sol–gel method. X-ray powder diffraction at room temperature indicates that our materials crystallize in the orthorhombic structure with Pbnm space group. The compounds undergo a second-order magnetic transition from paramagnetic to ferromagnetic state around their own Curie temperatures T C ~ 310, 270 and 230 K for X = Ce, Eu and Y, respectively. A considerable magnetocaloric effect (MCE) is observed around room temperature. The maximum values of magnetic entropy change ∆S max are 3.54, 3.81 and 2.99 J/kgK for the samples with X = Ce, Eu and Y, respectively, when a magnetic field of 5 T was applied. The relative cooling power (RCP) values for the corresponding materials are 246.60, 261.66 and 298 J/kg. It is shown that for Pr0.5X0.1Sr0.4MnO3 the exponent n and the magnetic entropy change follow a master curve behavior. With the universal scaling curve, the experimental ∆S at several temperatures and fields can be extrapolated.

Effect of K-doping on the structural, magnetic and magnetocaloric properties of Pr0.8Na0.2–xKxMnO3 (0 ≤ x ≤ 0.15) manganites

In this paper, the effect of potassium “K” substitution on morphological, crystallographic and magnetic properties of the Pr0.8Na0.2MnO3 perovskite was investigated. All samples were synthesized using the Pechini sol–gel method. On the one hand, the morphological study showed that the grains are irregularly spherically-shaped and have a submicronic size. On the other hand, the chemical analysis expectedly unveiled the presence of all the predicted elements in the right composition. Through the X-ray diffraction analysis, we proved that the prepared compounds crystallize in the orthorhombic structure with the Pbnm space group. The temperature dependence of the magnetization M (T) showed a large increase of M when x increases from 0 to 0.05, as does the Curie temperature TC. The transition from ferromagnetic (FM) to charge ordered antiferromagnetic (CO-AFM) phase at high temperature is observed for x = 0, however the doped manganites exhibit only an FM metallic phase. The magnetocaloric effect (MCE) was calculated according to the Maxwell relation based on magnetic measurements. The magnetic entropy change (ΔSM) reaches a maximum value which remains constant when increasing the K content. The highest value of the relative cooling power RCP was found to be 277 J/kg for the Pr0.8Na0.05K0.15MnO3 under an applied magnetic field of 5 T.

Effect of small quantity of chromium on the electrical, magnetic and magnetocaloric properties of Pr0.7Ca0.3Mn0.98Cr0.02O3 manganite

Structural, electrical and thermomagnetic properties of Pr0.7Ca0.3Mn0.98Cr0.02O3 were investigated. Sample was prepared by solid-state reaction method. X-ray diffraction revealed that the sample crystallizes in the orthorhombic system with Pnma space group. Electrical conductivity and complex impedance studies of Pr0.7Ca0.3Mn0.98Cr0.02O3 system are analyzed. The investigated compound exhibits a semiconductor behavior in the whole explored temperature range. From 100 to 206 K, the increase in DC conductance is more than two decade. At higher temperatures, the conductance varies slowly and a saturation region appears. The conduction mechanism is found to be governed by small polaron hopping process which is explained by the short range thermally activated energy. Conductance spectrum is well described by Jonsher law, and the temperature dependence of the frequency exponent confirms that conduction mechanism is governed by hopping process of the localized carriers. Using complex impedance analysis, the compound is modeled by an electrical equivalent circuit. Also, such analysis confirms the contribution of grain boundary to the transport properties. The substitution of Mn by 2 % Cr destroyed the charge order state observed in the parent compound and induced a ferromagnetic phase at low temperatures. For a magnetic field change of 5 T, the material shows a maximum magnetic entropy change |∆S max| = 2.69 J kg−1 K−1 with a full width at half maximum δ TFWHM = 145 K, and a relative cooling power RCP = 389 J kg−1. Pr0.7Ca0.3Mn0.98Cr0.02O3 material demonstrates potential proprieties to be used in electronic and thermal devices and as magnetic refrigerant.