Modified room‐temperature magnetic and optical properties in bilayer xBi₆Fe₂Ti₃O₁₈ − (1−x)CoFe₂O₄ composite thin films

Heterogeneous bilayer of Aurivillius compound Bi₆Fe₂Ti₃O₁₈ (BFTO) and Cubic spinel structure CoFe₂O₄ (CFO), a class of highly effective multiferroic composites, have been synthesized on fused quartz substrate by sol–gel method. Both BFTO and CFO layers are synthesized separately without any chemical reaction which can be confirmed by XRD pattern and Raman spectroscopy for two individual sets of maps. SEM and AFM images also verify two separate layers by showing the boundary between two layers clearly. Furthermore, linear increased ferromagnetism with increasing CFO component has been detected, further proving the independence of BFTO and CFO phases. Non-linear changed electron transition energy has been observed which may be derived from the crystal field distortion at the interface of the two layers. Therefore, an appropriate component can be found which have both excellent magnetic and optical properties, showing great potential on solar-energy conversion devices and multiferroic applications. In addition, variable temperature transmission spectra have been detected and the results are worth to be analyzed deeply.