Effect of the Oxygen Deficiency on the Structural, Magnetic and Electrical Properties in Perovskite-Like La0.6Sr0.4MnO3- delta (original) (raw)
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Physica Status Solidi (a), 2001
Subject classification: 61.66.Fn; 72.80.Jc; S10.15 Structural, magnetic and electrical properties of oxygen-deficient La 0.6 Sr 0.4 MnO 3--d with 0 d 0.20 are presented. X-ray diffraction reveals a two-phase region separating a rhombohedral phase stable over 0 d 0.127 and an orthorhombic phase stable in the range 0.15 d 0.20. Transport and magnetic studies indicate that the magnetic coupling and the electronic properties are strongly dependent on the oxygen deficiency d. Rhombohedral samples are ferromagnetic with Curie temperature T C varying with d; T C reached a maximum of 367 K for d = 0.025 which corresponds to a 54% Mn 4+ /Mn 3+ ratio. Orthorhombic samples present an antiferromagnetic order. The magnetic interactions between manganese ions are estimated; their sign and magnitude confirms the obtained magnetic properties. The study of the electrical properties shows a semiconductor to metal transition as the temperature is lowered from 300 to 80 K for samples with oxygen vacancy 0 d 0.10. A semiconductor behavior for La 0.6 Sr 0.4 MnO 2.873 and an insulator one for 0.15 d 0.20 are observed throughout the total temperature range studied. The electronic phase diagram in the plane of the temperature vs. oxygen deficiency d has been deduced from the magnetic and electrical measurements.
Journal of Solid State Chemistry, 2002
An intense e4ort has recently been devoted to studying the interplay between structure, magnetism, and transport in manganese perovskite Ln 1؊x A x MnO 3 (Ln ؍ La, Pr, Nd, Sm; A ؍ Ca, Ba, Sr). As a function of temperature, applied magnetic 5eld, doping, A-site ionic radius 1r A 2, and A-site size disorder, this system displays a rich phase diagram for both magnetotransport and structural properties. We have investigated the structural, magnetic, and transport properties of (La 1؊x Nd x ) 0.7 Sr 0.3 MnO 3 . The crystal structure was examined by X-ray powder di4raction which indicated that all the samples were single phase and revealed a transition from rhombohedral to orthorhombic structure with increasing x. The magnetization and resistivity investigation shows that for all values of x, (La 1؊x Nd x ) 0.7 Sr 0.3 MnO 3 are ferromagnetic+metallic at low temperatures and paramag-netic+semiconductor above the Curie temperature T c .
Materials Science and Engineering: B, 2007
We have investigated the effect of nominal strontium deficiency on the structure and the magnetic properties of La 0.6 Sr 0.4−δ MnO 3 (0 ≤ δ ≤ 0.3) manganese perovskites. The polycrystalline samples have been elaborated by the conventional ceramic method at 1573 K. The morphology, grain sizes and chemical analysis were analyzed by scanning electron microscope (SEM) and energy dispersive X-ray (EDX) techniques. The refinement of the structure by the Rietveld method revealed that most of these compounds crystallize in a rhombohedral (R3c) perovskite structure. Magnetization as a function of temperature, M(T), shows that these compounds exhibit a paramagnetic (PM) to ferromagnetic (FM) phase transition with decreasing temperature. The Curie temperature (T C ) decreases from 361 K to nearly the room temperature (292 K) with decreasing nominal strontium content. In the paramagnetic region the inverse of the magnetic susceptibility was fitted by a Curie-Weiss law. Magnetization as a function of magnetic field, M(H), measured at 50 K shows that all compounds are FM with a maximum in the magnetic saturation moment for the nominal value δ = 0.12. A comparative analysis shows that nominal vacancies, δ, cannot generally be achieved by our conventional ceramic method and results in a shift of the perovskite manganite composition compensated by the formation of an additional Mn 3 O 4 phase.
The European Physical Journal B, 2004
The crystal structure, magnetization and electrical transport depending on the temperature and magnetic field for the doped stoichiometric La 3+ 1−x Sr 2+ x Mn 3+ 1−x Mn 4+ x O 2− 3 as well as anion-deficient La 3+ 1−x Sr 2+ x Mn 3+ O 2− 3−x/2 (0 ≤ x ≤ 0.30) ortomanganite systems have been experimentally studied. It is established that the stochiometric samples in the region of the 0 ≤ x ≤ 0.125 are an O-orthorhombic perovskites whereas in the 0.175 ≤ x ≤ 0.30-a rhombohedric. For the anion-deficient system the symmetry type of the unit cell is similar to the stoichiometric one. As a doping level increases the samples in the ground state undergo a number of the magnetic transitions. It is assumed that the samples with the large amount of oxygen vacancies are a cluster spin glasses (0.175 < x ≤ 0.30) and temperature of the magnetic moment freezing is ∼40 K. All the anion-deficient samples are semiconductors and show considerable magnetoresistance over a wide temperature range with a peak for the x = 0.175 only. Concentration dependences of the spontaneous magnetization and magnetic ordering temperature for the anion-deficient La 3+ 1−x Sr 2+ x Mn 3+ O 2− 3−x/2 system have been established by the magnetic measurements and compared with those for the stoichiometric La 3+ 1−x Sr 2+ x Mn 3+ 1−x Mn 4+ x O 2− 3 one. The magnetic propeprties of the anion-deficient samples may be interpreted on the base of the superexchange interaction and phase separation (chemical disorder) models.
Journal of Solid State Chemistry, 2000
We present the oxygen de5ciency e4ects on the structural, magnetic, and electrical properties in La 0.7 Sr 0.3 MnO 3؊ ) solution where ) is a vacancy and 04 40.15. Polycrystalline samples La 0.7 Sr 0.3 MnO 3؊ ) were synthesized by a new method. In this series of manganites the Mn 3؉ content is systematically increased due to the increase in the nonstoichiometry . X-ray di4raction analysis shows a phase transition from a rhombohedral to an orthorhombic system at 0.0754 40.1. The material is ferromagnetic for 04 40.1 and antiferromagnetic for 0.1254 40.15. The Curie temperature T C and saturation magnetization M s decrease with increasing . Resistivity measurements as a function of temperature show a remarkable behavior for the La 0.7 Sr 0.3 MnO 2.9 compound; it is ferromagnetic metallic for 1154T4180 K and becomes ferromagnetic insulator below 115 K, where a charge ordering seems to appear. The di4erence in the hopping energies in our samples can be related to the existence of two crystallographic structures, one orthorhombic and the other rhombohedral.
An intense e4ort has recently been devoted to studying the interplay between structure, magnetism, and transport in manganese perovskite Ln 1؊x A x MnO 3 (Ln ؍ La, Pr, Nd, Sm; A ؍ Ca, Ba, Sr). As a function of temperature, applied magnetic 5eld, doping, A-site ionic radius 1r A 2, and A-site size disorder, this system displays a rich phase diagram for both magnetotransport and structural properties. We have investigated the structural, magnetic, and transport properties of (La 1؊x Nd x ) 0.7 Sr 0.3 MnO 3 . The crystal structure was examined by X-ray powder di4raction which indicated that all the samples were single phase and revealed a transition from rhombohedral to orthorhombic structure with increasing x. The magnetization and resistivity investigation shows that for all values of x, (La 1؊x Nd x ) 0.7 Sr 0.3 MnO 3 are ferromagnetic+metallic at low temperatures and paramag-netic+semiconductor above the Curie temperature T c .
Journal of Solid State Chemistry, 2000
We present the oxygen deficiency effects on the structural, magnetic, and electrical properties in La 0.7Sr 0.3MnO 3- δ□ δ solution where □ is a vacancy and 0≤ δ≤0.15. Polycrystalline samples La 0.7Sr 0.3MnO 3- δ□ δ were synthesized by a new method. In this series of manganites the Mn 3+ content is systematically increased due to the increase in the nonstoichiometry δ. X-ray diffraction analysis shows a phase transition from a rhombohedral to an orthorhombic system at 0.075≤ δ≤0.1. The material is ferromagnetic for 0≤ δ≤0.1 and antiferromagnetic for 0.125≤ δ≤0.15. The Curie temperature TC and saturation magnetization Ms decrease with increasing δ. Resistivity measurements as a function of temperature show a remarkable behavior for the La 0.7Sr 0.3MnO 2.9 compound; it is ferromagnetic metallic for 115≤ T≤180 K and becomes ferromagnetic insulator below 115 K, where a charge ordering seems to appear. The difference in the hopping energies in our samples can be related to the existence of two crystallographic structures, one orthorhombic and the other rhombohedral.
The Origin of Oxygen Vacancies Controlling La2/3 Sr1/3 MnO3 Electronic and Magnetic Properties
Advanced Materials Interfaces, 2016
magnetic, orbital, and structural degrees of freedom to deliver exotic magnetic and electronic phases that coexist. Desirable tunable properties, such as colossal magnetoresistance and half-metallicity of La 1x Sr x MnO 3 , a prototype of the family of Re 1x A x MnO 3 , are promising for multifunctional devices, such as solid oxide fuel cells, all-oxide spin FETs, magnetic tunnel junctions, and multiferroic memory. [ 10-12 ] However, oxygen vacancies will be readily induced in perovskite oxide thin fi lms during deposition and will play a crucial role on regulating the electronic and magnetic properties of perovskite oxide thin fi lms. [ 13 ] The effects of the oxygen vacancies on the properties of the oxide fi lms have two aspects. On one hand, oxygen vacancies can bring out novel phenomena and various possibilities for multifunctional device applications, [ 14-17 ] in which oxygen vacancies can move through the fi lms and modify the structural properties around them. The effects of the oxygen vacancies have not been clear yet. On the other hand, oxygen vacancies induce the degraded ferromagnetism and transport properties in mixed-valence manganite fi lms. [ 18-23 ] Full spin polarization and half-metallicity, which are required to reach high spin injection effi ciency in spintronic devices, are damaged in oxygen defi cient fi lms. In these
Journal of Superconductivity and Novel Magnetism, 2013
We have investigated the structural, magnetic, and electrical transport properties of a series of ABO 3 -type perovskite compounds, La 0.67 Sr 0.33 Mn 1−x V x O 3 (0 ≤ x ≤ 0.15). The samples were characterized by X-ray diffraction and data were analyzed using Rietveld refinement technique, it has been concluded that these materials have the rhombohedral structure with R3C space group. The magnetization and resistivity measurements versus temperature proved that all our samples exhibit a ferromagnetic to paramagnetic transition and a metallic to semiconductor one when the temperature increases. Both the Curie temperature T C and the resistivity transition temperature T P of the composites decrease, while the resistance increases as the V content increases. It has been concluded that the electrical conduction mechanism in the metallic regime at low temperatures (T < T P ) can be explained on the basis of grain boundary effects and the single electron-magnon scattering process. Resistivity data were well fitted with the relation ρ = ρ 0 + ρ 2 T 2 + ρ 4.5 T 4.5 , whereas the adiabatic Small Polaron Hopping (SPH) and Variable Range Hopping (VRH) models are found to fit well in the paramagnetic semiconducting regime at the high temperature (T > T P ).