... In the family of perovskite manganites Ln 1−x A x MnO 3 (Ln is a rare earth ion and A is a do... more ... In the family of perovskite manganites Ln 1−x A x MnO 3 (Ln is a rare earth ion and A is a doping ion) exhibiting the colossal magneto resistance (CMR) effect, compounds in which a trivalent rare-earth ions partially replaced by a monovalent alkali-earth ions rather than by a ...
In this paper, we report the structural, electrical, and magnetic properties of polycrystalline L... more In this paper, we report the structural, electrical, and magnetic properties of polycrystalline La 0.85– x Sm x Na 0.15 MnO 3 ( x = 0.05, 0.1, 0.15) manganites. Rietveld refinement of x-ray data infers that doped manganite compounds possess a rhombohedrally distorted structure (space group $R\bar 3C$ ). Both lattice parameter and unit cell volume decrease and a systematic change in both Mn–O–Mn bond angle and tolerance factor is observed with Sm content. Resistivity measurements discern metal–insulator transition ( T P ). For x = 0.15 sample, a double metal–insulator transition with a single ferromagnetic transition is depicted. All samples exhibit extrinsic magnetoresistance (MR) effect. A large value of MR of 65% (253 K, 8 T) is associated with grain and grain boundary formation. The highest low-field MR of 23% (12 K, 2 T) and 35.2% (23 K, 2 T) for x = 0.05 and 0.1 is observed. The electronic and magnetic inhomogeneities induced by Sm and nonmagnetic metal Na phases account for MR properties.
An investigation designed to exhibit the resistivity behaviour of La0.7Ca0.25K0.05MnO3 manganites... more An investigation designed to exhibit the resistivity behaviour of La0.7Ca0.25K0.05MnO3 manganites by formulating an effective inter-ionic interaction potential (EIoIP) with the long-range Coulomb, van der Waals interaction and the short-range repulsive interaction within the Hafemeister and Flygare approach to determine the Debye and Einstein temperature. The results obtained reveal that the resistivity mechanism is not only dominated by electron- phonon
In this paper, we report the structural, electrical, and magnetic properties of polycrystalline L... more In this paper, we report the structural, electrical, and magnetic properties of polycrystalline La 0.85– x Sm x Na 0.15 MnO 3 ( x = 0.05, 0.1, 0.15) manganites. Rietveld refinement of x-ray data infers that doped manganite compounds possess a rhombohedrally distorted structure (space group $R\bar 3C$ ). Both lattice parameter and unit cell volume decrease and a systematic change in both Mn–O–Mn bond angle and tolerance factor is observed with Sm content. Resistivity measurements discern metal–insulator transition ( T P ). For x = 0.15 sample, a double metal–insulator transition with a single ferromagnetic transition is depicted. All samples exhibit extrinsic magnetoresistance (MR) effect. A large value of MR of 65% (253 K, 8 T) is associated with grain and grain boundary formation. The highest low-field MR of 23% (12 K, 2 T) and 35.2% (23 K, 2 T) for x = 0.05 and 0.1 is observed. The electronic and magnetic inhomogeneities induced by Sm and nonmagnetic metal Na phases account for MR properties.
Structural properties of the polycrystalline La1-xKxMnO3 (x = 0.1, 0.125 and 0.15) are studied. T... more Structural properties of the polycrystalline La1-xKxMnO3 (x = 0.1, 0.125 and 0.15) are studied. These compounds having a rhombohedrally distorted structure with space group R3C. Both the lattice parameter and unit-cell volume decrease with increase in the K content due to the increase in Mn4+ content with doping, which is smaller (ionic radii, 0.53 A˚) than the Mn3+ ion (ionic radii, 0.645 A˚). There is a systematic change in both the Mn-O-Mn bond angle and the tolerance factor with K content and the crystal structure transforms to cubic-like symmetry.
ABSTRACT The electrical conduction in both metallic and semiconducting phase of La1-xKxMnO3 (x = ... more ABSTRACT The electrical conduction in both metallic and semiconducting phase of La1-xKxMnO3 (x = 0.05, 0.1, 0.15) is investigated. The phonon frequencies are estimated from the ab initio theory with calibrated Hamiltonian for the atomic interaction between a pair such as Mn-O and La/K-O including van der Walls interaction. The classical electron-phonon model of resistivity, i.e., the Bloch-Gruneisen (BG) model consistently retraces the reported metallic resistivity behavior. The paramagnetic semiconducting nature is discussed with thermal activation, small polaron conduction and Mott's variable range hopping model. The comparison of experimental data appears favorable with the present analysis.
... In the family of perovskite manganites Ln 1−x A x MnO 3 (Ln is a rare earth ion and A is a do... more ... In the family of perovskite manganites Ln 1−x A x MnO 3 (Ln is a rare earth ion and A is a doping ion) exhibiting the colossal magneto resistance (CMR) effect, compounds in which a trivalent rare-earth ions partially replaced by a monovalent alkali-earth ions rather than by a ...
Abstract The present work reports Rietveld refinement of X-ray powder diffraction, Raman study of... more Abstract The present work reports Rietveld refinement of X-ray powder diffraction, Raman study of La 1− x Na x MnO 3 ( x = 0.075, 0.125, 0.15) manganites and low temperature Raman of La 0.925 Na 0.075 MnO 3 . All Raman active phonon modes predicted by the group theory were observed. The A 1 g mode is substantially shifted with increasing Na substitution. The shifting is attributed to the fact that the variation of 〈 r A 〉 caused an internal pressure in the lattice. A change in the frequency of E g modes is also observed. We have analyzed the frequencies and widths of the observed Raman modes as a function of temperature for La 0.925 Na 0.075 MnO 3 . The sample shows a drastic change in Raman spectra and frequency shift between 300 K and 100 K, which attributed to magnetic ordering experience by the sample at low temperature. We observed the splitting of the rotational modes at 100 K that probably caused by the large orthorhombic distortion found in doped rhombohedral manganites.
... In the family of perovskite manganites Ln 1−x A x MnO 3 (Ln is a rare earth ion and A is a do... more ... In the family of perovskite manganites Ln 1−x A x MnO 3 (Ln is a rare earth ion and A is a doping ion) exhibiting the colossal magneto resistance (CMR) effect, compounds in which a trivalent rare-earth ions partially replaced by a monovalent alkali-earth ions rather than by a ...
In this paper, we report the structural, electrical, and magnetic properties of polycrystalline L... more In this paper, we report the structural, electrical, and magnetic properties of polycrystalline La 0.85– x Sm x Na 0.15 MnO 3 ( x = 0.05, 0.1, 0.15) manganites. Rietveld refinement of x-ray data infers that doped manganite compounds possess a rhombohedrally distorted structure (space group $R\bar 3C$ ). Both lattice parameter and unit cell volume decrease and a systematic change in both Mn–O–Mn bond angle and tolerance factor is observed with Sm content. Resistivity measurements discern metal–insulator transition ( T P ). For x = 0.15 sample, a double metal–insulator transition with a single ferromagnetic transition is depicted. All samples exhibit extrinsic magnetoresistance (MR) effect. A large value of MR of 65% (253 K, 8 T) is associated with grain and grain boundary formation. The highest low-field MR of 23% (12 K, 2 T) and 35.2% (23 K, 2 T) for x = 0.05 and 0.1 is observed. The electronic and magnetic inhomogeneities induced by Sm and nonmagnetic metal Na phases account for MR properties.
An investigation designed to exhibit the resistivity behaviour of La0.7Ca0.25K0.05MnO3 manganites... more An investigation designed to exhibit the resistivity behaviour of La0.7Ca0.25K0.05MnO3 manganites by formulating an effective inter-ionic interaction potential (EIoIP) with the long-range Coulomb, van der Waals interaction and the short-range repulsive interaction within the Hafemeister and Flygare approach to determine the Debye and Einstein temperature. The results obtained reveal that the resistivity mechanism is not only dominated by electron- phonon
In this paper, we report the structural, electrical, and magnetic properties of polycrystalline L... more In this paper, we report the structural, electrical, and magnetic properties of polycrystalline La 0.85– x Sm x Na 0.15 MnO 3 ( x = 0.05, 0.1, 0.15) manganites. Rietveld refinement of x-ray data infers that doped manganite compounds possess a rhombohedrally distorted structure (space group $R\bar 3C$ ). Both lattice parameter and unit cell volume decrease and a systematic change in both Mn–O–Mn bond angle and tolerance factor is observed with Sm content. Resistivity measurements discern metal–insulator transition ( T P ). For x = 0.15 sample, a double metal–insulator transition with a single ferromagnetic transition is depicted. All samples exhibit extrinsic magnetoresistance (MR) effect. A large value of MR of 65% (253 K, 8 T) is associated with grain and grain boundary formation. The highest low-field MR of 23% (12 K, 2 T) and 35.2% (23 K, 2 T) for x = 0.05 and 0.1 is observed. The electronic and magnetic inhomogeneities induced by Sm and nonmagnetic metal Na phases account for MR properties.
Structural properties of the polycrystalline La1-xKxMnO3 (x = 0.1, 0.125 and 0.15) are studied. T... more Structural properties of the polycrystalline La1-xKxMnO3 (x = 0.1, 0.125 and 0.15) are studied. These compounds having a rhombohedrally distorted structure with space group R3C. Both the lattice parameter and unit-cell volume decrease with increase in the K content due to the increase in Mn4+ content with doping, which is smaller (ionic radii, 0.53 A˚) than the Mn3+ ion (ionic radii, 0.645 A˚). There is a systematic change in both the Mn-O-Mn bond angle and the tolerance factor with K content and the crystal structure transforms to cubic-like symmetry.
ABSTRACT The electrical conduction in both metallic and semiconducting phase of La1-xKxMnO3 (x = ... more ABSTRACT The electrical conduction in both metallic and semiconducting phase of La1-xKxMnO3 (x = 0.05, 0.1, 0.15) is investigated. The phonon frequencies are estimated from the ab initio theory with calibrated Hamiltonian for the atomic interaction between a pair such as Mn-O and La/K-O including van der Walls interaction. The classical electron-phonon model of resistivity, i.e., the Bloch-Gruneisen (BG) model consistently retraces the reported metallic resistivity behavior. The paramagnetic semiconducting nature is discussed with thermal activation, small polaron conduction and Mott's variable range hopping model. The comparison of experimental data appears favorable with the present analysis.
... In the family of perovskite manganites Ln 1−x A x MnO 3 (Ln is a rare earth ion and A is a do... more ... In the family of perovskite manganites Ln 1−x A x MnO 3 (Ln is a rare earth ion and A is a doping ion) exhibiting the colossal magneto resistance (CMR) effect, compounds in which a trivalent rare-earth ions partially replaced by a monovalent alkali-earth ions rather than by a ...
Abstract The present work reports Rietveld refinement of X-ray powder diffraction, Raman study of... more Abstract The present work reports Rietveld refinement of X-ray powder diffraction, Raman study of La 1− x Na x MnO 3 ( x = 0.075, 0.125, 0.15) manganites and low temperature Raman of La 0.925 Na 0.075 MnO 3 . All Raman active phonon modes predicted by the group theory were observed. The A 1 g mode is substantially shifted with increasing Na substitution. The shifting is attributed to the fact that the variation of 〈 r A 〉 caused an internal pressure in the lattice. A change in the frequency of E g modes is also observed. We have analyzed the frequencies and widths of the observed Raman modes as a function of temperature for La 0.925 Na 0.075 MnO 3 . The sample shows a drastic change in Raman spectra and frequency shift between 300 K and 100 K, which attributed to magnetic ordering experience by the sample at low temperature. We observed the splitting of the rotational modes at 100 K that probably caused by the large orthorhombic distortion found in doped rhombohedral manganites.
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Papers by Dr.Neha Dodiya