Structural, electro-magnetic and electrical analysis in monovalent doped Nd0.75Na0.25-xKxMnO3 manganites

The polycrystalline Nd0.75Na0.25-xKxMn1O3 (x = 0, 0.05 and 0.10) samples were prepared using solid state reaction method. K doped manganites have been investigated to study its effect on crystalline phase and surface morphology as well as electrical transport and magnetic properties. However most of study show inconsistent result regarding to the electrical transport and magnetic properties as well as crystalline phase and morphology study. Thus, further detailed study need to be conducted in order to explain the properties of manganites. The structured properties of the Nd0.75Na0.25-xKxMnO3 manganite have been characterized using X-ray diffraction measurement showing the crystalline phase of samples were single phased and indexed as orthorhombic structure (Pnma space group). The morphological study from scanning electron microscope showed that there were improvements on the grains boundaries and sizes as well as the compactness with K doping. On the other hand, DC electrical resistivity measurement showed all samples exhibit insulating behavior. Analysis of dlnρ/dT-1 vs. T revealed a peak at temperature 210K for x = 0 and the peaks were shifted to the lower temperature around 190 K and 165 K for x = 0.05 and x = 0.1 respectively. Meanwhile, the investigation on magnetic behavior showed all samples exhibit transition from paramagnetic phase to anti-ferromagnetic phase with decreasing temperature and the TN was observed to shift to lower temperature. Apart from that, the electrical analysis; variable range hopping (VRH) model was selected in order to explain the electrical behavior of the samples as the value of R2 is approached to 0.9999 as it has highest value compared to small polaron hoping (SPH) model. In conclusion, the effect of K+ doped on Nd0.75Na0.25-xKxMn1O3 were effected the properties of manganites including the structure, surface morphology, magnetic and electrical due to the different ionic radius and reduction in the distortion of MnO6 octahedral

Observation of charge ordering signal in monovalent doped Nd0.75Na0.25-xKxMn1O3 (0 ≤ x ≤ 0.10) manganites

K doping in the compound of Nd0.75Na0.25-xKxMn1O3 (x = 0, 0.05 and 0.10) manganites have been investigated to study its effect on crystalline phase and surface morphology as well as electrical transport and magnetic properties. The structure properties of the Nd0.75Na0.25- xKxMnO3 manganite have been characterized using X-ray diffraction measurement and it proved that the crystalline phase of samples were essentially single phased and indexed as orthorhombic structure with space group of Pnma. The morphological study from scanning electron microscope showed there was an improvement on the grains boundaries and sizes as well as the compactness with K doping suggestively due to the difference of ionic radius. On the other hand, DC electrical resistivity measurement showed all samples exhibit insulating behavior. However, analysis of dlnρ/dT-1 vs. T revealed the clearly peaks could be observed at temperature 210K for x = 0 and the peaks were shifted to the lower temperature around 190 K and 165 K for x = 0.05 and x = 0.1 respectively, indicate the existence of charge ordering (CO) state in the compound. Meanwhile, the investigation on magnetic behavior showed all samples exhibit transition from paramagnetic phase to anti-ferromagnetic phase with decreasing temperature and the TN was observed to shift to lower temperature suggestively due to weakening of CO stat

Crystalline phase, surface morphology and electrical properties of monovalent-doped Nd0.75Na0.25Mn1-yCoyO3 manganites

Perovskite-type manganites Nd0.75Na0.25Mn1-yCoyO3 (y = 0 – 0.05) have been investigated to clarify the influence of Co-doped on crystal phase and morphological study as well as electrical transport properties. The Nd0.75Na0.25Mn1-yCoyO3 samples are prepared via solid state synthesis method. X-ray diffraction analysis revealed all the samples are essentially single phased and the peaks are indexed to an orthorhombic structure with Pnma space. The morphological study from scanning electron microscope shows the improvement of the grains boundaries and sizes as well as the compaction of particles can be seen as cobalt doping increased. On the other hand, the temperature dependence of electrical resistivity measurements using four-point-probe technique indicates all samples maintained an insulator like behaviour down to low temperature. Analysis of the resistivity change with respect to temperature, dlnρ/dT-1 versus T reveals a slope changes of resistivity has been observed and a boarder peak exist for y = 0 sample and the peaks become significantly obvious for y = 0.02 and 0.05 samples. The peaks are observed in the range of charge ordering (CO) transition indicate the existence of CO in the system

Crystalline Phase, Surface Morphology and Electrical Properties of Monovalent-doped Nd0.75Na0.25Mn1-yCoyO3 Manganites

Perovskite-type manganites Nd0.75­Na­0.25­Mn­1-yCo­y­O­3­ (y = 0 – 0.05) have been investigated to clarify the influence of Co-doped on crystal phase and morphological study as well as electrical transport properties. The Nd­0.75­Na­0.25­Mn­1-yCo­y­O­3­ samples are prepared via solid state synthesis method. X-ray diffraction analysis revealed all the samples are essentially single phased and the peaks are indexed to an orthorhombic structure with Pnma space. The morphological study from scanning electron microscope shows the improvement of the grains boundaries and sizes as well as the compaction of particles can be seen as cobalt doping increased. On the other hand, the temperature dependence of electrical resistivity measurements using four-point-probe technique indicates all samples maintained an insulator like behaviour down to low temperature. Analysis of the resistivity change with respect to temperature, dlnÏ/dT-1 versus T reveals a slope changes of resistivity has been observed and a boarder peak exist for y = 0 sample and the peaks become significantly obvious for y = 0.02 and 0.05 samples. The peaks are observed in the range of charge ordering (CO) transition indicate the existence of CO in the system

Effect of Co3+ substitution on electro-magnetic properties of Pr0.75Na0.25mno3 and Nd0.75Na0.25mno3 manganites

This paper reports influences of cobalt (Co) substituted at Mn-site of Pr0.75Na0.25Mn1-xCoxO3 and Nd0.75Na0.25Mn1-yCoyO3 on structure, electrical transport and magnetic properties. All of the samples were prepared via standard solid state reaction method. X-ray diffraction measurement indicates that all samples were crystallized in an orthorhombic structure (space group Pnma). Resistivity measurement displays the x = 0 sample manifests an insulator behavior while metal-insulator transition was found at 108 K and 84 K for x = 0.02 and 0.05 respectively for Pr0.75Na0.25Mn1-xCoxO3. On the other hand, all of the samples for Nd0.75Na0.25Mn1-yCoyO3 showed insulator behavior down to low temperature and analysis of the resistivity change with respect to temperature, dlnρ/dT -1 versus T reveals a slope changes of resistivity have been recorded. Two obvious peaks were recorded from the analysis for y = 0.02 and 0.05 which can be suggested to the existence of charge order transition at the vicinity. For magnetic properties, x = 0 sample showed a paramagnetic-antiferromagnetic transition and further substitution of Co, x = 0.02 and 0.05, induce the paramagnetic-ferromagnetic transition and antiferromagnetic arrangement respectively. Meanwhile, further substitution of Co, y = 0.02 and 0.05 indicate antiferromagnetic transition with increasing TN as Co increased