Investigation of Multiferroic properties of the Co doping SrBi$_{2}$Nb$_{2}$O$_{9}$

Multiferroics (MF) are novel class of next generation multifunctional materials, however there are very few single-phase MF materials existing in nature. Thin films (TF) of (Sr$_{x}$Co$_{1-x})$Bi$_{2}$Nb$_{2}$O$_{9}$ (SCBN) with x = 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3 with thickness $\sim $400 nm were fabricated from individual SCBN targets on Pt/Ti/SiO$_{2}$/Si substrate by pulsed laser deposition technique. The x-ray diffraction studies revealed orthorhombic structure of SCBN for up to 20{\%} Co doped TF without any phase segregation, the splitting in (200) peak was observed above 25{\%} of Co doping. The room temperature (RT) Raman spectra of SCBN TF showed SrBi$_{2}$Nb$_{2}$O$_{9 }$ peaks in all compositions, however additional modes appeared in the 600-800 cm$^{-1 }$frequency region. The dielectric constant of all SCBN films showed linear frequency dispersion above 1 kHz, and their values are in the range of 400 to 650 at 1 kHz. An increase in tangent loss from $\sim $ 0.040 to 0.135 at 1 kHz was observed with increase in Co concentration. All SCBN TF show well defined hysteresis loop with remanent polarization of about 16 $\mu $C/cm$^{2}$. However, less saturation in the ferroelectric loop was observed with increase of Co content. Both magnetic and magneto-electric behavior of TF along with the ferroelectric properties will be discussed.