Raman spectra, photoluminescence, magnetism and magnetoelectric coupling in pure and Fe doped BaTiO_3 nanostructures

摘要

Structural, microstructural, Raman spectroscopy, photoluminescence, saturation magnetization and magnetoelectric (ME) measurement of BaTiO_3 (BFTO) and BaFe_(0.01)Ti_(0.99)O_3 (BFT1) nanostructures have been studied. BFTO and BFT1 were prepared by a hydrothermal method of processing temperature 180 °C/ 48 h. The X-ray diffraction pattern shows the coexistence of cubic/tetragonal and hexagonal phases for BFTO and cubic/tetragonal for BFT1. The Raman spectra confirm the coexistence of tetragonal and hexagonal phases in BFTO and cubic in BFT1. Transmission electron microscopy images show nanorods of hexagonal shaped faces for BFTO and cubic shaped nanowires for BFT1. The resulting mechanism of the formation of these nanostructures is discussed. The experimental and theoretical results by photoluminescence are related to the degree of disorder existing in both BFTO and BFT1 and suggest the presence of localized states existing inside of the band gap which are directly affected for degree of order-disorder. A strong ferromagnetism in BFT1 and diamagnetism in BFTO is observed by magnetic hysteresis. As BFT1 is ferromagnetic, the value of linear coefficient, α called Magnetoelectric (ME) coefficient is calculated as ~16 mV/Oe cm at a fixed frequency of 850 Hz. This ME coefficient α corresponds to induction of polarization by a magnetic field or of magnetization by an electric field. The observed optimum dc bias field at which the maximum ME coupling occurs is ~750 Oe.