Magnetic Properties Of Pr Research Articles

The magnetocaloric and magnetic properties of Pr0.7Sr0.3MnO3 film on Pb(Mg1/3Nb2/3)0.7Ti0.3O3

The magnetocaloric and magnetic properties of Pr0.7Sr0.3MnO3 film on Pb(Mg1/3Nb2/3)0.7Ti0.3O3

Influence of Bi3+ substitution on the structural and magnetic properties of Pr0.6Sr0.4MnO3 ceramics

We report the structural and magnetic phase transition induced in Pr0.6Sr0.4MnO3 as Pr3+ ions are replaced by Bi3+. Analysis of Rietveld refinement of the X-ray diffraction data reveals a change in crystal symmetry from orthorhombic, space group Pnma for x ≤ 0.20 to Imma for x > 0.50. Across intermediate Bi3+ substitution (0.25 ≤ x ≤ 0.40), a structural phase coexistence of Pnma and Imma symmetry is found. Based on the combined studies of electrical and magnetic properties, a magnetic phase diagram for Bi substituted Pr0.6Sr0.4MnO3 samples is proposed here. The electrical resistivity and magnetization studies for partial Bi3+ substituted samples x ≤ 0.10 indicate samples to be ferromagnetic metallic with TC = 310 K and 290 K for x = 0.0 and 0.10 respectively. As Bi3+ concentration increases, TC decreases, and the system transforms to be antiferromagnetic insulating with TN = 158 K for x = 0.60 accompanied by a spin glass like state below 10 K. For samples with intermediate Bi3+ concentrations i.e., 0.25 ≤ x ≤ 0.40, field induced metamagnetic magnetization loops (M vs. H) imply the competitive coexistence of ferromagnetic and antiferromagnetic interactions in the same matrix. Also, the open loops in field dependent resistance curves (MR vs. H) for 0.20 ≤ x ≤ 0.40, specify the field induced transition from insulating to metallic state. The magnetoresistance improves on increasing Bi3+, with MR% reaching a maximum of 100% for 0.20 ≤ x ≤ 0.30 samples.

Effect of nanoscale size reduction on the magnetic properties of Pr0.6Sr0.4MnO3

The ferromagnetic Pr0.6Sr0.4MnO3 sample has been subjected to time bound high energy planetary ball milling with an aim to reduce the particle size. When the particle size is analyzed as a function of milling time, it is found that particle size decreases with increasing milling time and then saturates at a certain value. The implications of the decrease in particle size on magnetic properties have been carefully studied by analyzing the magnetization data in detail. With a decrease in particle size, the Curie temperature, TC and the magnitude of magnetization drops. A deviation in inverse magnetic susceptibility from the Curie-Weiss behaviour has been noticed for nanoparticles which suggest the presence of quenched disorder due to particle size reduction. The strength of magnetic interactions switches from long range to short range with a systematic decrease in particle size. The observed properties can be explained considering the core–shell structure of the nanoparticle where the surface defects strongly influence the degree of disorder in the system.

First principal calculation and Monte Carlo simulations of the Magnetocaloric effect, Electronic and Magnetic properties in perovskite oxide Pr 0.65Sr 0.35MnO 3

We have used the first principal calculation and Monte Carlo simulations (MCS) to investigate the magnetocaloric effect, electronic and magnetic properties of Pr 0.65Sr 0.35MnO 3 (PSMO) perovskite. The exchange-correlation potential was treated with the generalized gradient approximation (GGA) for the electronic and magnetic properties. The ferromagnetic phase of PSMO is half metallic with 100% spin polarization, which is important in the relation to the colossal magnetoresistance properties of this compound. The magnetic moment is obtained. The thermal variation of magnetization of PSMO has been obtained. The temperature dependence of the magnetic entropy change and the adiabatic temperature are obtained by MCS. The Curie temperature of PSMO has been deduced. The field dependence of relative cooling power PSMO has been obtained.

Critical behavior of Pr0.65Sr0.35MnO3 compound investigated by a Monte Carlo Simulation

The critical behavior and magnetic properties of Pr0.65Sr0.35MnO3 (symbolized here by PSMO) were studied using Monte Carlo Simulation (MCS). The thermal bath algorithm and Ising model in which exchange interactions via the third nearest neighbor were used to calculate the magnetic and magneto-caloric properties. The effects of temperature (T) and external magnetic field (h) on the magnetic behavior of PSMO were examined. The results show that the Curie temperature (TC) is close to the experimental value. The magnetic entropy shows a maximum value around the TC that increases linearly with the increase of the external field. The critical behavior of the PSMO compound was studied by analyzing the magnetization isotherms and by exploiting Arrott plots. The obtained values of the critical exponents are β = 0.336, γ = 1.121, and δ = 4.335. These values are very close to those reported for the 3D-Ising model. The variation of maximum magnetic entropy (ΔSmmax) and relative cooling power (RCP) around the Curie temperature were calculated; the obtained values of ΔSmmax and those of RCP ranging from 3.612 and 92.7 for 1T to 6.191 and 209.9 for 5T, respectively. These results are sufficiently interesting to consider the PSMO compound as a promising candidate for magnetic refrigeration.

Correlation of microstructure with magnetic properties in Pr0.67Sr0.33MnO3 thin films

Strain can be used to modulate magnetic properties of manganite thin film by affecting not only its crystal structure but also the microstructure, including the cluster size and fraction of ferromagnetic phase. In this work, epitaxial Pr0.67Sr0.33MnO3 thin films deposited on (001)-SrTiO3 single-crystal substrate are studied. The magnetization-temperature curves with zero-field cooling and field cooling show the typical feature of cluster-glass system. With the increase of film thickness, strain relaxation occurs in 80 nm Pr0.67Sr0.33MnO3 film with a wide temperature range of phase transition. By fitting the freezing temperature Tf dependence on magnetic field according to Almeida–Thouless equation, the 80 nm film has a larger local anisotropy and exchange bias compared to that of the 15 nm Pr0.67Sr0.33MnO3 film. Detailed analysis suggests that the strain-induced phase fraction and size distribution of ferromagnetic phase are responsible for the different magnetic properties of Pr0.67Sr0.33MnO3 film with different thickness.

Influence of Ruthenium Doping on the Crystal Structure and Magnetic Properties of Pr0.67Ba0.33Mn1–xRuxO3 Manganites

This study reports the structural, morphological, and magnetic properties of ruthenium doping at the manganese site in Pr0.67Ba0.33MnO3 manganites. Rietveld refinement X-ray powder diffraction (XRD) data show that Pr0.67Ba0.33MnO3 and Pr0.67Ba0.33Mn0.9Ru0.1O3 crystallize in an orthorhombic perovskite structure with the Pnma space group. Doping with Ru yields an increment in the lattice parameter and unit cell volume. In addition, small changes in the Mn–O–Mn bond angle and bond distance are observed. Field emission scanning electron microscopy (FESEM) is used to examine the surface morphology of the samples. Fourier transform infrared spectroscopy (FTIR) reveals that the Mn–O and metal–oxygen bonds appear at the 600 and 900 cm−1 bands, respectively. The AC magnetic susceptibility measurement studies confirm that a paramagnetic (PM) to ferromagnetic (FM) transition exists at 130 and 153 K for the Pr0.67Ba0.33MnO3 and Pr0.67Ba0.33Mn0.9Ru0.1O3 samples, respectively.

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.

Impact of Gd Doping on the Microstructural-, Electronic-, Magnetotransport, and Magnetic Properties of Pr0.6Gd0.1Sr0.3MnO₃ Nanomanganite.

Gadolinium doping effects on structural-, electronic transport and magnetic properties of Pr0.6Gd0.1Sr0.3MnO₃ (PGSMO) nanomanganite (40-65 nm) have been investigated. We have considered the core-shell structure of our PGSMO nanoparticles, which can explain its intriguing magnetic and transport properties. It is reported 65 nm sample exhibits higher metal to insulator transition temperature, TP (∼215 K) and less resistive behavior compare to its nano counterparts. Enhanced low-field magnetoresistance (LFMR) is observed with a reduction of particle size; however maximum change in magnetoresistance (MR), ∼72% is recorded for 65 nm sample around TP at 60 kOe field. Low-temperature magnetization data reveals the existence of glassy phase in the compound. It is revealed that substitution of optimal Gd doping at A site on nanometric scale promotes exotic magnetic and transport properties on nanoscale without adding any external physical perturbation or introducing any significant lattice distortion.

Phase composition and magnetic properties of Pr–Nd–MM–Fe–B nanocrystalline magnets prepared by spark plasma sintering

The isotropic nanocrystalline [(PrNd)0.8MM0.2]29.8Fe68.7Al0.1Cu0.12Co0.88B magnets (MM: mischmetal) were prepared by single-main phase and double-main phase methods using spark plasma sintering (SPS). Melt-spinning method was used to prepare initial powder and avoid component deviations caused by longtime ball milling. The magnetic properties of the magnet prepared by double-main phase method (called double-main phase magnet, DMP magnet) are remanence of Br = 0.75 T, intrinsic coercivity of Hcj = 909.83 kA·m−1, maximum magnetic energy product of (BH)max = 95.48 kJ·m−3, which are better than those of the magnet prepared by single-main phase method (called single-main phase magnet, SMP magnet). The diffraction peaks of the main phase of DMP magnet split in X-ray diffractometer (XRD) pattern, indicating that R2Fe14B phases with different distributions of La/Ce elements exist in the magnet. This speculation is confirmed by transmission electron microscopy (TEM) observation. The La/Ce-rich main phase and La/Ce-lean main phase are present in DMP magnets. The heterogeneity of rare earth elements suppresses the magnetic dilution effect in DMP magnet, and the magnetic properties are improved. Though the DMP magnet contains different main phases, it presents unitary Curie temperature (TC) of 577 K, which is higher than that of SMP magnet. This result suggests that the TC of the magnets can be promoted by double-main phase method and SPS.

An investigation on microstructural, spectral and magnetic properties of Pr–Cu double-substituted M-type Ba–Sr hexaferrites

This is first report on Pr–Cu double-substituted M-type Ba–Sr hexaferrites with nominal compositions Ba0.3Sr0.7−xPrxFe12.0−xCuxO19 (x = 0.00–0.35) fabricated by the solid-state reaction route. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FE-SEM) and Hysteresis graph meter were used to characterize the synthesized M-type Ba–Sr hexaferrites. XRD results show that the hexaferrites with x ≤ 0.21 exhibited single M-type phase, while the hexaferrites with x ≥ 0.28 exhibited the M-type phase and impurity phases. FE-SEM images proposed that all particles with hexagonal platelet-like shape were homogeneously dispersed. The remanence (Br) first increased with Pr–Cu content (x) from 0.00 to 0.14, and then decreased when x ≥ 0.14. The intrinsic coercivity (Hcj) and magnetic induction coercivity (Hcb) first decreased with x from 0.00 to 0.14, and then increased when x ≥ 0.14. Maximum energy product [(BH)max] reached the maximum value at x = 0.14.

Synthesis, structure and magnetic properties of Pr0.65Ca0.3M0.05MnO3 (M = Na, K and Ag): A perovskite manganites with metamagnetic phase transitions

The synthesis, structural characterization, and magnetic properties of Pr0.65Ca0.3M0.05MnO3 (M = Na, K and Ag) perovskite manganites are reported. Our samples were synthesized using the solid state reaction method at high temperature. Rietveld refinements of the X-ray diffraction patterns show that all our samples are single phase and crystallize in the distorted orthorhombic system with Pbnm space group. The surface morphology and infrared absorption of the samples were systematically investigated. Magnetization measurements versus temperature in a magnetic applied field of 50 mT showed that the antiferromagnetic ordering temperature TAFM occurring below the charge-ordering transition temperature TCO in these narrow band manganites are slightly dependent with monovalent element. The critical magnetic field (Hc) required for metamagnetism is found to reduce drastically from 7 T for Pr0.65Ca0.35MnO3 to 2.9 T for Pr0.65Ca0.3Na0.05MnO3.

Electronic structure and magnetic properties of Pr–Co intermetallics: ab initio FP-LAPW calculations and correlation with experiments

First-principle calculations combining density functional theory and the full-potential linearized augmented plane wave (FP-LAPW) method are performed to investigate the electronic and magnetic structure of Pr2Co7 in its two polymorphic forms, (2:7 H) and (2:7 R), for the first time. This type of calculation was also performed for PrCo5 and PrCo2 intermetallics. We have computed the valence density of states separately for spin-up and spin-down states in order to investigate the electronic band structure. This is governed by the strong contribution of the partial DOS of 3d-Co bands compared to the partial DOS of the 4f-Pr bands. Such a high ferromagnetic state is discussed in terms of the strong spin polarization observed in the total DOS. The magnetic moments carried by the Co and Pr atoms located in several sites for all compounds are computed. These results mainly indicate that cobalt atoms make a dominant contribution to the magnetic moments. The notable difference in the atomic moments of Pr and Co atoms between different structural slabs is explained in terms of the magnetic characteristics of the PrCo2 and PrCo5 compounds and the local chemical environments of the Pr and Co atoms in different structural slabs of Pr2Co7. From spin-polarized calculations we have simulated the 3d and 4f band population to estimate the local magnetic moments. These results are in accordance with the magnetic moments calculated using the FP-LAPW method. In addition, the exchange interactions Jij are calculated and used as input for M(T) simulations. Involving the data obtained from the electronic structure calculations, the appropriate Padé Table is applied to simulate the magnetization M(T) and to estimate the mean-field Curie temperature. We report a fairly good agreement between the ab initio calculation of magnetization and Curie temperature with the experimental data.

Charge ordering in B-site Mo doped Pr0.20Sr0.80Mn1−xMoxO3−δ

The temperature dependent structural, transport and magnetic properties of Pr0.20Sr0.80Mn1−xMoxO3−δ (x = 0.0, 0.02, 0.04 and 0.10) have been studied using low-temperature x-ray and electron diffraction, resistivity and dc magnetization measurements. Unlike the undoped (x = 0) sample, which is cubic at room temperature, the Mo doped samples show phase coexistence of cubic (Pm3¯m) and tetragonal (I4/mcm;c/2>a) phases. The Mo doping stabilizes the tetragonal (I4/mcm) phase in the temperature range of 300–330 K. The tetragonality of the sample for x = 0.10 however appears to be of different kind, which further under goes an additional transition from tetragonal to orthorhombic (Fmmm) phase below 200 K. Transmission electron microscopy, employing electron-diffraction and high-resolution micro-structural imaging, clearly reveals the occurrence of charge-ordering (CO) for x = 0.04 and 0.10 samples with non-integral modulation along [110] type perovskite direction. The dc magnetization and resistivity data very well correlate with the observed structural and associated CO antiferromagnetic phase transitions. The increased stability of the distorted perovskite phases and the occurrence of CO are found to correlate with the increase in the Mn3+/Mn4+ ratio as a function of Mo6+ substitution. The possible role of effective B-site cation size in stabilizing the distorted perovskite phase has been discussed in terms of tolerance factor.

Structural disorder effect on the structural and magnetic properties of Pr0.4Re0.1Sr0.5−yBayMnO3 manganites (Re = Pr, Sm, Eu, Gd, Dy and Ho)

Abstract The influence of the A-site cation size-disorder σ 2 on the structural and magnetic properties of the polycrystalline Pr 0.4 Re 0.1 Sr 0.5−y Ba y MnO 3 (Re = Pr, Sm, Eu, Gd, Dy and Ho) samples with a constant average ionic radius A > = 1.2445 A, is investigated. All samples were synthesized using the solid-state reaction. Rietveld refinement of the X-ray diffraction patterns shows that the substitution generates a structural transition from tetragonal to orthorhombic symmetry. The temperature dependence of magnetization indicates a weakening of ferromagnetism by the increase of σ 2 . The large difference between the field cooled and zero field cooled magnetization below Curie temperature suggests the presence of an inhomogeneous mixture of a ferromagnetic and antiferromagnetic domains at low temperature. The maximum of the magnetic entropy change decreases with increasing the mismatch effect. However, several peculiarities were observed in the magnetic behavior indicating that σ 2 is not the only factor controlling the physical properties; the nature and the magnetic moment of the substituent should be taken in consideration.

GGA + U Study of Electronic and Magnetic Properties of Pr(Fe/Cr)O3 Cubic Perovskites

First principles calculations based on density functional theory have been employed to study the structural, electronic and magnetic properties of Pr(Fe/Cr)O3 perovskite.The calculations were performed by fullpotential linearized augmented plane wave method with generalized gradient (GGA) and GGA + U approximations for the exchange and correlation functionals. The electronic properties show that PrCrO3 exhibits a complete half-metallic character for both approximations GGA and GGA + U with integer magnetic moment, while for PrFeO3, a metallic behavior with GGA is seen and a half-metallic attitude with GGA + U (for U ≥4eV) is depicted. It was found that Hubbard coefficient affects PrFeO3, while the value of eV is the most appropriate for PrCrO3.

Study of electrical and magnetic properties of Pr0.6−xBixSr0.4MnO3 (x=0.20 and 0.25)

We have investigated the electrical and magnetic properties of Pr0.6-xBixSr0.4MnO3 (x=0.20 and 0.25) manganites. XRD data shows that the synthesized samples are single-phase and crystallize in the orthorhombic structure with Pnma space group. Resistivity measurements show that the sample with x=0.25 exhibits a thermally activated behavior for the entire temperature range. The magnetoresistance (MR) for the x=0.25 sample is as high as nearly 100% over a wide range of temperature, demonstrating its important technological application as a material for MR-based devices. From the magnetization measurements, two magnetic transitions viz. paramagnetic insulating to ferromagnetic metallic (PMI-FMM) transition at TC and the ferromagnetic metallic (FMM) to antiferromagnetic insulating (AFI) transition at Neel temperature TN were observe in both samples. The Curie temperature decreases with bismuth doping, while TN increases with Bi content. Most interestingly, the temperature variation of magnetization and resistivity shows hysteresis behavior across the transition for the x=0.20 sample.

Enhanced grain surface effect on magnetic properties of Pr<SUB align="right">0.57Ca<SUB align="right">0.43MnO<SUB align="right">3 nanomanganite

In this paper, we study the enhanced grain surface effect on the magnetic properties of Pr0.57Ca0.43MnO3 (PCMO) nanomanganites. Nanoparticles OF PCMO were prepared by low cost sol-gel route and bulk sample was prepared by solid state reaction method. Crystallite size and structure of the samples were studied by X-ray diffraction (XRD) method. Surface morphology and compositional analysis were studied by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). Magnetisation measurements were carried out using superconducting quantum interference magnetometer (SQUID) in the temperature range of 10-300 K. The temperature dependence of field cooled magnetisation of bulk sample show charge order (CO) peak around 240 K and antiferromagnetic (AFM) transition at 170 K. Interestingly the charge order peak was found to be absent in 17 nm and 21 nm particles and both samples show ferromagnetic (FM) transition (TC) at 60 K and 90 K respectively. Melting of charge order and appearance of ferromagnetism in PCMO nanoparticles will be discussed with the help of core-shell model.

Electrical transport and magnetic properties of Pr0.7Sr0.3MnO3/La0.5Ca0.5MnO3 bilayer film on (001) SrTiO3

We have grown Pr0.7Sr0.3MnO3/La0.5Ca0.5MnO3 bilayer on (001) single crystal SrTiO3 substrate by pulsed laser deposition technique. The bilayer film is well (001) orientation grown with high crystalline quality. When the applied magnetic field increases up to 9 T, only metal-like transport behavior can be observed below room temperature. The Low-field MR (LFMR) as large as ~−73% has been achieved at an applied field of 1 T and the magnetoresistance (MR) can reach a value of ~−641% at an applied field of 9 T. Ferromagnetic (FM) clusters percolation accompanied with the collapse (melting) of charge-ordered (CO) state in La0.5Ca0.5MnO3 may be responsible for the enhancement of MR. Moreover, the disappearance of exchange bias (EB) in the bilayer demonstrates the existence of FM clusters percolation at the PSMO/LCMO interface. Large LFMR provides possibilities in developing manganite-based FM/CO film devices.

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.