Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8153700 | Journal of Magnetism and Magnetic Materials | 2018 | 37 Pages |
Abstract
In this study, we have investigated the structural, magnetic and thermoelectric properties of La0.4Bi0.4Ca0.2Mn1âxCoxO3 (0â¯â¤â¯xâ¯â¤â¯0.3) manganites. The crystallographic parameters of samples were determined by the Rietveld refinement of powder X-ray diffraction data. It was observed that Co doping results in change of crystal structures from orthorhombic (space group: Pbnm) to rhombohedral (space group: R-3c) symmetry. Scanning electron microscopy (SEM) images show smooth, clean and densified structures, depicting good crystallinity of samples. The zero field cooled (ZFC) and field cooled (FC) magnetization data were collected in the temperature range 5 to 300â¯K under an applied magnetic field of 0.1â¯Tesla. The analysis of temperature dependent magnetization data reveals all samples to be ferromagnetic with Curie temperatures aroundâ¯â¼77â¯K. The magnetic hysteresis loops, collected at 5â¯K, show that the saturation magnetization (MS) values decrease from 43â¯emu/g to 14â¯emu/g with increase in Co doping. The high temperature thermoelectric properties of all samples are characteristic of a semiconducting behavior, the small polaron hopping model fitting well with the temperature dependent electrical resistivity (Ï) and thermopower (S) data. The thermopower values change sign from positive to negative as temperature is increased from 313â¯K to 680â¯K. The maximum thermoelectric power factor (PFâ¯=â¯S2/Ï) obtained for xâ¯=â¯0.3 sample at 313â¯K is 4.60â¯Î¼W/mK2, is much higher than for the undoped sample.
Related Topics
Physical Sciences and Engineering
Physics and Astronomy
Condensed Matter Physics
Authors
Uzma Hira, Falak Sher,