Superconducting properties of Barium, BA substitution in BSCCO-2223 / Amirah Natasha Ishak

In this study, the superconducting properties of barium, Ba substitution in BSCCO2223 have been investigated by using four-point probe and X-ray Diffraction analysis. Ba was incorporated in the calcium, Ca2+ site with concentrations of x = 0.00, 0.02, 0.05 and 0.10. Samples of x = 0.02, 0.05 am 0.10 have higher Tc value compared to the pure BSCCO-2223 (x = 0.00). The optimum Ba concentration that has the highest Tc value which is 99 K is x = 0.05. It can be simplified that barium substitution in BSCCO-2223 enhances the Tc value. XRD pattern SIDWS a lot of improvement of the peaks since the low-peak (2212) decreases while high-peak (2223) increases with the increases of Ba concentratio

The physical properties of submicron and nano-grained La0.7Sr0.3MnO3 and Nd0.7Sr0.3MnO3 synthesised by sol–gel and solid-state reaction methods

La0.7Sr0.3MnO3 (LSMO) and Nd0.7Sr0.3MnO3 (NSMO) possess excellent colossal magnetoresistance (CMR). However, research work on the neodymium-based system is limited to date. A comparative study between LSMO and NSMO prepared by sol–gel and solid-state reaction methods was undertaken to assess their structural, microstructural, magnetic, electrical, and magneto-transport properties. X-ray diffraction and structure refinement showed the formation of a single-phase composition. Sol–gel-synthesised NSMO was revealed to be a sample with single crystallite grains and exhibited intriguing magnetic and electrical transport behaviours. Magnetic characterisation highlighted that Curie temperature (TC) decreases with the grain size. Strong suppression of the metal–insulator transition temperature (TMI) was observed and attributed to the magnetically disordered grain surface and distortion of the MnO6 octahedra. The electrical resistivity in the metallic region was fitted with theoretical models, and the conduction mechanism could be explained by the grain/domain boundary, electron–electron, and electron–magnon scattering process. The increase in the scattering process was ascribed to the morphology changes. Enhancement of low-field magnetoresistance (LFMR) was observed in nano-grained samples. The obtained results show that the grain size and its distribution, as well as the crystallite formation, strongly affect the physical properties of hole-doped manganites

Effect of NiO nanoparticle addition on the structural, microstructural, magnetic, electrical, and magneto-transport properties of La0.67Ca0.33MnO3 nanocomposites

Incorporation of the secondary oxide phase into the manganite composite capable of enhancing low-field magnetoresistance (LFMR) for viability in high-performance spintronic applications. Polycrystalline La0.67Ca0.33MnO3 (LCMO) was prepared via the sol–gel route in this study. The structural, microstructural, magnetic, electrical, and magneto-transport properties of (1−x) LCMO: x NiO, x = 0.00, 0.05, 0.10, 0.15 and 0.20 were investigated in detail. The X-ray diffraction (XRD) patterns showed the coexistence of LCMO and NiO in the composites. The microstructural analysis indicated the amount of NiO nanoparticles segregated at the grain boundaries or on the surface of LCMO grains increased with the increasing secondary phase content. LCMO and NiO still retained their individual magnetic phase as observed from AC susceptibility (ACS) measurement. This further confirmed that there is no interfacial diffusion reaction between these two compounds. The NiO nanoparticle acted as a barrier to charge transport and caused an increase in resistivity for composite samples. The residual resistivity due to the grain/domain boundary is responsible for the scattering mechanism in the metallic region as suggested by the theoretical model fitting, ρ(T)=ρ0+ρ2T2+ρ4.5T4.5. The magnetoresistance values of LCMO and its composites were found to increase monotonically with the decrease in temperature. Hence, the LFMR was observed. Nonetheless, the slight reduction of LFMR in composites was attributed to the thick boundary layer created by NiO and impaired the spin polarised tunnelling process

Structural and electrical properties of La0.7Ca0.3MnO3 /α-Fe2O3 composites

Colossal magnetoresistive (CMR) materials have huge potential in modern application and it has been widely used in magnetic sensing industry. From the literature, an incorporation of secondary insulating phase into mixed-valence manganites could improve its extrinsic effect especially low-field magnetoresistance (LFMR). However, nanoparticle addition could lead to substitution and diffusion with its parent compound. In this work, the structural and electrical properties of La0.7Ca0.3MnO3 (LCMO) were investigated by adding the α-Fe2O3 nanoparticle with ratio of 0.00, 0.05, 0.10, 0.15 and 0.20 as the artificial grain boundaries. The LCMO compound has been synthesised using sol-gel route. The samples were chosen to sinter at 800°C to obtain the pure LCMO phase by referring to the thermogravimetric analysis (TGA). The structural properties were investigated by an X-ray diffractometer (XRD) while electrical properties were measured by a four-point probe (4PP) system. XRD patterns showed the coexistence of two phases (LCMO & α-Fe2O3). LCMO crystallised in orthorhombic structure with space group Pnma while α-Fe2O3 exhibited in hexagonal form with space group R-3c. As the content of α-Fe2O3 increases, the resistivity of the samples increases drastically. Nevertheless, the addition of iron oxide has no significant effect on the metal-insulator transition temperature (T­MI). From the XRD and 4PP analysis, it can be deduced that the α-Fe2O3 nanoparticles do not react with LCMO compound and successfully formed the La0.7Ca0.3MnO3 /α-Fe2O3 composites. The resistivity increases when the nano-sized α-Fe2O3 is added into LCMO nanocomposites due to the insulator nature of α-Fe2O3

Structural, electrical, and magneto-transport properties of Pr0.7Sr0.3MnO3: Al2O3 composites

Incorporation of insulating secondary phase into manganite composites can enhance the low-field magnetoresistance (LFMR). This work reports the structural and electrical transport properties of (1-x) Pr0.7Sr0.3MnO3 (PSMO): x Al2O3 composites synthesised by solid-state reaction method. X-ray diffraction (XRD) patterns indicated that Mn-O-Mn bond distance and angle were disturbed due to the substitution of Al3+ at Mn-site of PSMO system. This subsequently increased the resistivity of composite samples and shifted the metal-insulator transition temperature (TMI) to lower temperatures as increasing content of Al2O3. LFMR effect was observed as the magnetoresistance values increase monotonically with the decreasing temperature