Archives of Metallurgy and Materials

Abstract

MnO 3 polycrystalline were synthesized from La 2 O 3 , CaO and MnO 2 powder mixture using a solid state reaction technique. The compound powders were obtained through the free sintering method at different temperatures and sintering times in order to study the influence of technological conditions on Ca doped La manganites. The most important physical features as structure, microstructure and morphology were described after X-ray diffraction investigation. Photographs of the specimen fractures were taken with SEM (scanning electron microscope) and they revealed high porosity of the tested material and great tendency for its grains to create agglomerates. Influence of doping and technological conditions on lattice parameters were studied by means of Rietvield analysis. The XRD measurements reveal that La 0,7 Ca 0,3 MnO 3 has orthorhombic symmetry with Pnma space group.

Electrical and magnetic properties of La0.7Ca0.3MnO3 nanoparticle prepared by reactive milling method

“…As presented in figure 3(a), the experimental ρ(T) data of LCMO-NP sample in the temperature region of 30-300 K are well fitted to equation (7), the solid lines. This indicates that the conductivity of our sample can be well explained by the phase segregation model.…”

“…Meanwhile, in the semiconducting PM state, the resistivity of sample follows the law of the self-trapped small polaron hopping [33,34]. The parameters obtained from fitting ρ(T) data to equation (7) are listed in table 1. It can be seen that the values of ρ 0 , ρ 2 , ρ 4.5 , and E g decrease in the presence of a magnetic field of 4 kOe, resulting in reduced resistivity.…”

“…The spins in the polarons attempt to arrange along the external field, resulting in the weakened electron trap ability of the Table 1. Parameters estimated from fitting ρ(T) data to equation (7) in a range of 30-300 K of LCMO-NP sample. polarons and preventing the scattering of spin disorders, leading to a decrease in E g [35].…”

“…The hole-doped manganites with La 1−x A x MnO 3 formula (where A is a monovalent or divalent element) show lots of delightfully physical phenomena [1][2][3][4] because of a coexistence of Mn 3+ and Mn 4+ ions leading to the ferromagnetic (FM) double exchange (DE) interaction of Mn 3+ -Mn 4+ pairs, antiferromagnetic (AFM) super exchange (SE) interactions of Mn 4+ -Mn 4+ and Mn 3+ -Mn 3+ pairs. Particularly, the La 0.7 Ca 0.3 MnO 3 (LCMO) material is one of the 30% holedoped manganites with an optimal ratio of manganese valance Mn 3+ and Mn 4+ [5][6][7]. It possesses a high Curie temperature (T C =250-263 K) [1,8,9], high magnetoresistance (MR) [10][11][12] and magnetocaloric (MC) effects [9,13], and an unusual half-metallic feature [14].…”