Magnetic and optical studies on polyvinylpyrrolidone thin films doped with rare earth metal salts

Abstract

A casting technique was used to prepare new nanocomposite thin films of pure and GdCl3- or HoCl3-doped polyvinylpyrrolidone (PVP). Transmission electron microscopy (TEM) was used to study the particle size and dispersibility in the investigated nanocomposites. Magnetic measurements, using a vibrating sample magnetometer (VSM), were carried out at room temperature and applied magnetic fields up to 10 kOe. The appearance of hysteresis loops with small values of saturation flux density (Bs), remanent flux density (Br), squareness ratio (SQR) and coercive field (Hc), along with permeability (μ) values relatively higher than 1, may be taken, as a matter of experimentation, to consider the investigated composites as soft magnet materials. In this study, PVP-HoCl3 films showed slightly better magnetic properties compared with PVP-GdCl3 films. A comparative analysis of infrared (IR) and ultraviolet-visible spectra of the parent components and their composites indicated the effective role of dopant nature and concentration in morphological and microstructural changes occurring in the PVP matrix. Optical constants, such as the energy gap (Eg) and the Urbach tail (Ee), were determined and discussed in terms of a model based on the electronic transition between localized states in the band structure. Cast technique was used to prepare new nanocomposite thin films of pure and GdCl3- or HoCl3-doped polyvinylpyrrolidone (PVP) with different dopant concentrations. During magnetic measurements, using a vibrating sample magnetometer, carried out at room temperature and applied magnetic fields up to 10 kOe, thin films of the system PVP-HoCl3 showed slightly better magnetic properties than PVP-GdCl3. A comparative infrared and ultraviolet-visible spectral analysis of the parent components and their nanocomposites provided an indication to the effective role of dopant nature and concentration in morphological and microstructural changes occurring in the PVP matrix.