Physical Properties Of La0 Research Articles

La0.6X0.1Te0.3MnO3 system with significant refrigerant capacity at low magnetic field and double magnetic entropy change peaks: effect of ball-milling time on physical and critical behaviors

We have investigated the ball-milling time effect on different physical properties of La0.6X0.1Te0.3MnO3 (X is a lacuna) system (LT) milled for 1 h (LT-1h), 3 h (LT-3h), and 6 h (LT-6h). According to Williamson-Hall method, as the ball-milling duration is increased, the material’s crystallite size decreases from approximately 145 to 99 nm for LT-1h and LT-6h, respectively. Electronic study was also investigated. The Zero-Field-Cooling and Field-Cooling (ZFC/FC) magnetization measurements illustrated that all the systems are presenting a ferromagnetic to paramagnetic phase transition around Curie temperature (TC). This transition is around 176, 182, and 183 K accompanied by a decrease in the magnitude in both ZFC and FC data. Thus, increasing the ball-milling time of the sample leads to the elevation of TC and does not enhance the magnitude of the magnetization the fact that it affects the magnetic interactions between atoms. By increasing the ball-milling duration, the proportion of homogeneity is increased, and the material becomes slightly more resilient, according to the Curie-Weiss law. Additionally, it is accompanied with an increase in coercivity and a decrease in the saturation magnetization and remanence. Based on the AC-susceptibility, raising the ball-milling time facilitates the appearance of a spin-glass (SG) state. The relative cooling power (RCP) value in the LT-1h sample at 2 T is 108% (211.758 J kg−1) compared to that of the Gd at 2 T. Consequently, the LT sample could be a permanent magnet in a magnetic refrigerator. Noting that raising the ball-milling time weakens the RCP. Both LT-1h and LT-3h systems are belonging to the tricritical mean field model. However, for LT-6h, the model changed and the best one became the 3D-Ising model. Hence, the ball-milling time influences also the universality class.

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−xNixO3 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 TC (Curie temperature), which decreases from 354 K to 301 K. From the Arrott diagrams M2vs. μ0H/M, we can conclude the phase transition is of the second order. Based on measurements of the isothermal magnetization around TC, the magnetocaloric effects (MCEs) have been calculated. The entropy maximum change (−ΔSM) 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 (μ0H) of 5 T. Through these results, the La0.6Ba0.2Sr0.2Mn1−xNixO3 (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 TM–SC. The adiabatic small polaron hopping (ASPH) model is applied in the PM-semiconducting part (T > TMS). 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.

Influence of Ni doping on physical properties of La0.7Sr0.3FeO3 synthesized by reverse micelle technique

In the present work, a series of Ni-doped La0.7Sr0.3FeO3 perovskite nanostructures with chemical composition La0.7Sr0.3Fe1−xNixO3 (x = 0.0, 0.01 and 0.04) were synthesized by the reverse micelle (RM) technique. The X-ray diffraction (XRD) analysis verifies good crystallinity and an orthorhombic crystal structure of the samples. The remarkable growth of the crystallites was observed in increasing the amount of Ni doping. The morphology, topography, and chemical composition were investigated through field emission scanning electron microscope (FESEM) equipped with an energy dispersive X-ray spectrometer (EDS). The FESEM/EDS measurements confirm uniform morphology and interconnected nature of the particles with relevant elements. The Fourier transform infrared (FTIR) spectra further demonstrate the perovskite structure through Fe/Ni–O asymmetric stretching and deformation of Fe/Ni–O–Fe/Ni bending vibrations in the lattice. A systematic reduction in the bandgap (Eg) is noticed upon the Ni doping in La0.7Sr0.3FeO3, as estimated from the UV/visible spectra by employing the Tauc's relation. A distinct behaviour of dielectric properties was revealed as a function of frequency and temperature for all the samples. The dielectric constant (e′), dielectric loss (tanδ), and ac conductivity (σac) were measured at selected frequencies and temperatures. The results signify that the dielectric nature was frequency-dependent and thermally stimulated. The magnetic properties at room temperature indicate weak ferromagnetism with gradual increase in the maximum magnetization and coercivity with the increase in Ni concentration.

Influence of different post-annealing temperatures on physical properties of La0.72Ca0.28MnO3:Ag0.2 thin films by pulsed laser deposition technique

La0.72Ca0.28MnO3:Ag0.2/LaAlO3 (100) thin films, prepared by pulsed laser deposition, were post-annealed at different temperatures in air. X-ray diffraction technique were used to analysize the orientation and lattice parameter, atomic force microscope (AFM) and scanning electronic microscope (SEM) were employed to characterize the surface morphology of the thin films. Resistance vs. temperature (R-T) behaviors of the thin films were tested with standard four-probe technique. The surface morphology results show that the grain size increases and crystalline quality of the films are improved with increased annealing temperature up to 1200 °C, while the amount of grains also increases; R-T results illustrate that both the temperature coefficient of resistance (TCR) and metal-insulator transition temperature (TMI) of the films, increase with annealing temperature. In particular, TCR of thin film (post-annealing at 1200 °C) reaches 28.8%·K−1, which makes such films be promisingly applicated in thermal detectors near the room temperature.

Influence of Pellet Compaction Pressure on the Physical Properties of La0.7Ba0.3MnO3 Manganite

Influence of Pellet Compaction Pressure on the Physical Properties of La0.7Ba0.3MnO3 Manganite

Physical properties of La0.67Ca0.13Sr0.2Mn1−xFexO3 compounds doped Fe

Abstract La0.67Ca0.13Sr0.2Mn1−xFexO3 (x = 0–0.1) compounds were synthesised by standard sol-gel reaction and characterised by X-ray diffraction at room temperature. X-ray diffraction and Rietveld refinement show that they crystallize in the rhombohedral structure with the R 3 ‾ c space group. The magnetic behavior (magnetization and Curie temperature TC) shows a large dependence on the fractional composition x. The Mossbauer results reveal the presence of iron ion at the trivalent state Fe3+ assigned by the same isomer shift δ value. Resistivity measurements, performed between 10 and 350 K, show a metal–insulator transition for 0.0 ≤ x The suppression of metallic behavior and ferromagnetism under the doping effects of Fe will be discussed in terms of doping disorder, Fe-Mn super-exchange interactions and a site percolation mechanism.

Structural, magnetic and magnetocaloric investigation of La0.7−xDyxCa0.3MnO3 (x = 0.00, 0.01 and 0.03) manganite

La0.7−xDyxCa0.3MnO3 (x = 0.00, 0.01 and 0.03) compounds were prepared using sol–gel method. X- ray diffraction and magnetic measurements were used to investigate the effects of Dy doping on the physical properties of La0.7−xDyxCa0.3MnO3. XRD data have been analyzed by Rietveld refinement technique. Moreover they crystallized in an orthorhombic structure with Pnma space group. Magnetization as a function of temperature has shown that these compounds exhibit a transition from a ferromagnetic to paramagnetic phase with increasing temperature. The $$\Delta {\text{S}}_{{\text{M}}}^{{{\text{max}}}}$$ in a magnetic field change of 5 T is found to be 6.79, 10.15 and 3.97 J Kg−1 K−1 for x = 0.00, 0.01 and 0.03, respectively. At this value of magnetic field, the relative cooling power (RCP) is found to be 191, 155 and 157 J Kg−1 for x = 0.00, 0.01 and 0.03, respectively. Our result on magnetocaloric properties suggests that La0.7−xDyxCa0.3MnO3 (x = 0.00, 0.01 and 0.03) compounds are attractive as possible refrigerants for near room temperature magnetic refrigeration.

Physical properties of La0.7Ca0.2Sr0.1MnO3 manganite: a comparison between sol–gel and solid state process

We have synthesized La0.7Ca0.2Sr0.1MnO3 sample using two different methods: the solid-state reaction (S1) and the sol–gel process (S2). Structural, morphological, infrared and magnetic properties were investigated by X-ray diffraction, scanning electron microscopy, Spectrum Two FT-IR Spectrometer and vibrating sample magnetometer. Despite the various conditions employed in the elaboration, the crystallographic study shows that our samples are single phase and crystallize in orthorhombic system with Pnma space group. A small difference appears in the microstructural and magnetic properties. The Curie temperature TC is found to be 308–256 K for S1 and S2 respectively. A large magnetocaloric effect has been observed in both samples, besides; the relative cooling power for S2 is bigger than S1. It attains exactly 250.75 J kg−1 under a magnetic applied field of 5 T. These results show that the elaboration process has an important impact on the magnetic and magnetocaloric properties. Furthermore, the importance of the magnetoelastic coupling and electron interaction in the magnetocaloric properties of manganite was confirmed by the analysis of Landau theory.

Vacancy effect in both calcium and barium on the physical properties of La0.6Ca0.2Ba0.2MnO3 polycrystalline manganite

In this paper, we report the effect of both calcium and barium (5%) on the structural, magnetic and magnetocaloric properties of La0.6Ca0.2Ba0.2MnO3 (LCBMO) polycrystalline manganite. Our powder specimens were synthesized using the solid-state reaction method at high temperatures with an annealing temperature of 1200 °C. The X-ray diffraction patterns refined using Rietveld method confirm that our compounds are single phase and crystallize in the orthorhombic perovskite structure (Pbnm space group). Magnetization measurements versus temperature under low magnetic applied field (0.05 T) show a paramagnetic-ferromagnetic transition for both compounds. The Curie temperature TC is found to be 302, 202 and 295 K for LCBMO, La0.6Ca0.15□0.05Ba0.2MnO3 (LC) and La0.6Ca0.2Ba0.15□0.05 MnO3 (LB) samples respectively.Using magnetization measurements as a function of magnetic applied field up to 5 T at several temperatures, we deduced the magnetic entropy change ΔSM. The |−ΔSMmax|, under a magnetic field change of 5 T is found to be 2.4; 2.69 and 2.84 Jkg−1K−1 for LCBMO, LC and LB, respectively. The obtained results are compared to calculated ones based on the Landau theory and a good concordance is observed.

Effect of Terraces at the Interface on the Structural and Physical Properties of La0.8Sr0.2MnO3 Thin Films**Supported by the Strategic Priority Research Program (B) of Chinese Academy of Sciences under Grant No XDB07030200, the National High-Technology Research and Development Program of China under Grant No 2014AA032607, and the National Natural Science Foundation of China under Grant No 11404380.

Employing atomic force microscopy, transmission electron microscopy and the second harmonic generation technique, we carefully explore the structural properties of 6-unit-cell-thick La0.8Sr0.2MnO3 films grown on SrTiO3 with atomically fat TiO2-terminated terraces on the surface. The results clearly demonstrate that the terraces on the surface of TiO2-terminated SrTiO3 can improve the layer-by-layer epitaxial growth of the manganite films, which results in uniform film coverage at the beginning of growth and thus reduces the substrate-induced disorder at or near the interface. Comparing the magnetic and transport properties of La0.8Sr0.2MnO3 films with the thicknesses varying from 6 unit cells to 80 unit cells grown respectively on as-received SrTiO3 and TiO2-terminated SrTiO3, it is found that these atomically flat terraces on the surface of TiO2-terminated SrTiO3 can greatly enhance the Curie temperature and conductivities of the ultrathin La0.8Sr0.2MnO3 films with thickness less than 50 unit cells, while no obvious difference is detected in the magnetic and transport properties of the 80 unit-cell thick films.

Annealing Effect on the Physical Properties of La0.7Sr0.3MnO3 Thin Films Grown on Si Substrates Prepared by Chemical Solution Deposition Method

The LSMO films were prepared on Si substrates by chemical solution deposition method. The films were annealing in air and O2 atmosphere. All films have perfectly crystallized. Compared with the LSMO films annealing in air, the residual and saturation magnetic moment value were much lower for the films annealing in O2. The Tc of the LSMO films annealing in O2 is higher about 15 K than that annealing in air. The variation of magnetization and Tc with annealing in O2 is thus consistent with the change of Sr content and is almost certainly related to the Mn3+/Mn4+ ratio. The MR value is decreased with the increasing temperature. It is observed that the transport properties, both the resistivity and the magnetoresistance value, have similar variation behavior. It is because that the La(Sr) vacancies (δ > 0) are expected to have indirect perturb the conduction path. The resistivity and the MR value at 7 T of the both films are (0.145 Ω.cm, 59.3%), (0.208 Ω.cm, 60.0%), respectively.

Analysis of the microstructure and physical properties of La0.85Sr0.15Ga0.8Mg0.2O2.825 and Ce0.85Sm0.15O1.925 composite electrolytes used in solid oxide fuel cells

(100–xwt%) La0.85Sr0.15Ga0.8Mg0.2O2.825 (LSGM1520)+(xwt%) Ce0.85Sm0.15O1.925 (SDC15)(x=0, 2, 5, 7, 10, and 100) composite electrolytes were synthesized by a solid-state reaction. The microstructures and electrical properties of the electrolytes were analyzed by X-ray diffractometry, Raman spectroscopy, scanning electron microscopy, thermomechanical analysis, and impedance spectroscopy. The electrolytes, LSGM1520 and 95wt% LSGM1520–5wt% SDC15, based on a La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF6428) cathode and Ce0.8Sm0.2O1.9–Ni (SDC20-Ni) cathode were used to form two SOFCs. The thermal expansion coefficients of the composites ranged from 10.5×10−6/°C to 12×10−6/°C at 200–600°C and 12×10−6/°C to 15×10−6/°C at 600–800°C. The performances and current density of LSCF6428/LSGM1520/SDC20-Ni and LSCF6428/95L05S/SDC20-Ni are 264mW/cm2 and 1.00A/cm2 at 774°C, and 182mW/cm2 and 0.97A/cm2 at 789°C, respectively, and their open circuit voltages (OCV) are ∼1.0–1.1V.

Effect of the oxygen deficiency on the physical properties of La0.8Na0.2MnO3−δ oxides (δ=0 and 0.05)

This paper presents the effects of oxygen deficiency on the structural, magnetic and magnetocaloric properties of La0.8Na0.2MnO3−δ where δ=0 and 0.05. The Polycrystalline La0.8Na0.2MnO3−δ samples were synthesized by a new method. The introduction of the oxygen deficiency in our samples leads to an increase of Mn3+ content according to the electronic formula La0.3+Na0.2+Mn0.6+2δ3+Mn0.4−2δ4+O3−δ.The X-ray diffraction analysis shows a phase transition from a rhombohedral system with R3¯c space group for δ=0.00 to an orthorhombic with Pnma space group for δ=0.05. It also induces a great variation in the magnetic properties. The magnetization versus temperature study has shown that all samples exhibit a magnetic transition from ferromagnetic (FM) to paramagnetic (PM) phase with the increase in temperature. However, it can be clearly seen that the oxygen deficiency induces an increase in the magnetization and a decrease in the Curie temperature TC. Besides, the magnetocaloric effect (MCE) as well as the Relative Cooling Power (RCP) has been estimated. As an important result, the values of MCE and RCP in our oxygen deficiency manganites are reported to be close to those found in gadolinium that is considered as magnetocaloric reference material.

Effect of thickness variation on the physical properties of La0.85Te0.15MnO3 thin films grown on LaAlO3 (001) by pulsed laser deposition

We report the effect of thickness on the structural, morphological, transport and magnetic properties of perovskite oxide La0.85Te0.15MnO3 thin films grown on LaAlO3 (001) single crystal substrate by pulsed laser deposition. We have observed that the transport and magnetic properties of the films depend on the film thickness, surface morphology, and epitaxial strain. The films were characterized by x-ray diffraction that confirms that the films have good crystalline quality, single phase and c-axis orientation. The Atomic force microscopic (AFM) results show that surface roughness and average grain size increase with film thickness. The resistivity measurements show an insulator to metal transition that correlates well with the magnetic ordering temperature. X-ray photoemission spectroscopy measurements suggests that Te ions are in the Te4+ state, while the Mn ions stay in the Mn2+ and Mn3+ valence states.

Correction: Effect of Ru substitution on the physical properties of La0.6Pr0.1Sr0.3Mn1−xRuxO3 (x = 0.00, 0.05 and 0.15) perovskites

Correction for ‘Effect of Ru substitution on the physical properties of La0.6Pr0.1Sr0.3Mn1−xRuxO3 (x = 0.00, 0.05 and 0.15) perovskites’ by N. Zaidi et al., RSC Adv., 2015, 5, 31901–31909.

The effect of Dy doped on structural, magnetic and magnetocaloric properties of La0.67−xDyxPb0.33MnO3 (x=0.00, 0.15 and 0.20) compounds

La0.67−xDyxPb0.33MnO3 (x=0.00, 0.15 and 0.20) compounds were prepared using solid-state reaction. X-ray diffraction and magnetic measurements were used to investigate the effects of Dy doping on the physical properties of La0.67−xDyxPb0.33MnO3. XRD data have been analyzed by Rietveld refinement technique. Results have shown that all obtained perovskite manganites were a single phase. Moreover they crystallized in a rhombohedric structure with R3¯c space group. Magnetization as a function of temperature has shown that these compounds exhibit a transition from a ferromagnetic to paramagnetic phase with increasing temperature. A magnetocaloric effect in the obtained samples has been deduced by two methods: Classical Maxwell relation and Landau theory. The maximum of magnetic entropy change |ΔSMmax| in a magnetic field change of 5T is found to be 4.26Jkg−1K−1 at 360K, 3.51Jkg−1K−1 at 290K and 2.3Jkg−1K−1 at 277K for x=0.00, 0.15 and 0.20, respectively. At this value of magnetic field, the relative cooling power (RCP) is found to be 292, 246 and 215Jkg−1 for x=0.00, 0.15 and 0.20, respectively. Our result on magnetocaloric properties suggests that La0.67-xDyxPb0.33MnO3 (x=0.00, 0.15 and 0.2) compounds are attractive as possible refrigerants for near room temperature magnetic refrigeration.

Erratum to: Study of the Magneto-Resistivity and Dependence of Percolation in La0.75Ca0.1Sr0.15Mn1−x Ga x O3 Compounds

We present a study of the effect of Ga-doping on the physical properties of La0.75Ca0.1Sr0.15Mn1−xGaxO3 (x=0.025, 0.075 and 0.1) compounds prepared by the sol-gel method. The variation of the magnetization (M) vs. temperature (T), under an applied magnetic field of 0.05 T, reveals a ferromagnetic–paramagnetic transition for all samples. The magnetization behavior and the Curie temperature TC have shown a large dependence on the fractional composition x. In fact, the M(T) curves have revealed the presence of a long-range ferromagnetic state below TC.

Synthesis and Physical Properties of La0.53Ca0.26Ba0.21Mn0.77Ti0.21Zr0.02O3 Multiferroic Material

This work reports the synthesis, structural characterization, ferroelectric and magnetic behavior of the La0.53Ca0.26 Ba0.21Mn0.77Ti0.21Zr0.02O3 (LCBMTZ) complex perovskite. The material is obtained by the solid state reaction method. Rietveld refinement of X-ray diffraction experiments shows that the material crystallizes in a tetragonal perovskite structure, space group P4mm (#99). Impedance spectroscopy measurements give evidence of ferroelectricity with high values of electric permittivity (e′=119.2) and electrical polarization curves confirm it. Measurements of magnetic hysteresis loops at 10 and 150 K reveal a ferromagnetic behavior. On the other hand, the comparison of the FC and ZFC magnetization and resistivity measurements shows different magnetic regimes associated with changes in the resistivity. The analysis of these curves suggests the existence of magnetoelectric coupling in temperature regimes below 228.09 K.

Effect of monovalent doping on the physical properties of La0.7Sr0.3MnO3 compound synthesized using sol-gel technique

In this work, we have studied the effect of monovalent substitution on the structural, magnetic and magnetocaloric properties of the P-doped La0.7Sr0.2M0.1MnO3 (M = Na, K) manganites synthesized by sol-gel technique. Structural investigations using X-ray diffraction show that all the elaborated compounds crystallize in the rhomboedral structure with R-3c space group. The increase in the ionic radius <rA> induces a rotation of MnO6 octahedra leading to a change in the Mn-O-Mn angles and the Mn-O distances. Magnetizations measurements were carried out using vibrating sample magnetometer operating above room temperature with magnetic applied field up to 5 tesla. All our samples exhibit paramagnetic to ferromagnetic transition with a Curie temperature above room temperature. From magnetic measurements versus magnetic applied field at several temperatures, we have determined the magnetocaloric effect using the classical thermodynamics based on Maxwell relations.

Physical properties of La0.7Ba0.3MnO3−δ complex oxide thin films grown by pulsed laser deposition technique

We report on transport properties of oxide manganite La0.7Ba0.3MnO3−δ (LBMO) thin films deposited by pulsed laser deposition (PLD) technique. Detailed analysis of heavy-ion stoichiometric composition has been carried out as a function of laser-pulse fluence and ambient oxygen pressure. Depositions using high-fluence (6 J/cm2) and low oxygen pressure (10−2 mbar) provide the optimal heavy-ion stoichiometric ratio in the LBMO samples. Deviations from the optimal LBMO stoichiometry are observed when decreasing the laser fluence or increasing the background oxygen pressure. This behavior is interpreted by considering the influence of the experimental deposition conditions on the plume dynamics. All these findings provide clear insights on the PLD-growth of manganites and, more in general, of complex oxide materials.