Room temperature ferromagnetic behavior, linear and nonlinear optical properties of KNbO3 microrods

Microrods of potassium niobate (KNbO3) were synthesized at 700, 800 and 900 °C by solid state reaction method and their structural, morphological, linear optical, nonlinear optical and magnetic properties were studied. X-ray diffraction and Rietveld refinement reveal that all the prepared KNbO3 samples belong to single phase orthorhombic structure with space group of Cm2m. Fourier transform infrared and Raman spectral analyses confirmed the Nb-O symmetric stretching vibrational modes of NbO6 octahedron. The grain growth direction (001) and inter planar spacing (0.38 nm) of KNbO3 were determined by high resolution transmission electron microscopy. Field emission scanning electron microscopy images revealed that KNbO3 are formed with nearly rod shape morphology with average diameter varying from 471 to 678 nm and length lies between 1.2 and 2.3 µm. X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy studies confirmed the presence of K, Nb and O elements in the KNbO3 matrix. UV-visible diffuse reflectance spectra showed that the band gap of KNbO3 microrods varies between 3.18 and 3.22 eV. The existence of blue (492 nm) and green (521 nm) emissions evidently showed the presence of oxygen vacancy in the samples. All the synthesized KNbO3 microrods exhibited relatively high SHG efficiency as compared with that of the standard KDP. Vibrating sample magnetometer analysis showed the existence of ferromagnetic behavior at room temperature. The saturation magnetization (Ms) of KNbO3 microrods lies between 0.015 and 0.012 emu g−1 and coercive field (Hc) varies in the range from 489 to 420 Oe.