Magnetic Properties Of Electrospun La_1-xca_xmno₃ Nanowires

In this thesis, a preliminary study was made for fabrication and magnetic properties of La1-xCaxMnO3 nanowires by electrospinning technique. Main results are follows:We first made the PVA-La1-xCaxMnO3 composite microfibers by electropinning, and subsequently obtained La1-xCaxMnO3 nanowires with perovskite structure through sintering at enhanced temperatures. The influences of different fabrication parameters (concentration of the solution, voltage, flowing rate, etc), and different sintering conditions (temperature, time) on the morphology of samples were studied during electrospinning process. The optimal sintering condition for La1-xCaxMnO3 nanofibers is available.All nanowires showed the characteristics of spin glass based on the magnetic measurement results (M-T and M-H curves). In contrast, the M-T curve of La0.75Ca0.25MnO3 powders does not show the characteristics of spin glass, implying the "dimension effect" works.The bimodal phenomena have been observed on the electron spin resonance spectra of both La0.75Ca0.25MnO3 nanowires and La0.75Ca0.25MnO3 powder samples. The La0.75Ca0.25MnO3 nanowires show the paramagnetic state embedded in the ferromagnetic context in the vicinity of Curie temperature and below, while the ferromagnetic state embedded in the paramagnetic context for the powder sample. This similar phenomenon of magnetic phase separation was failed to appear in La0.5Ca0.5MnO3 and La0.33Ca0.67MnO3 nanowires.