Study of band structure, transport and magnetic properties of BiFeO3–TbMnO3 composite

Abstract

Charge transfer across the interface of two materials in a composite can create reconstruction of bands near the interface which in turn brings multiple changes in physical properties of the materials. Thus, investigation of band structure experimentally is of immense importance in studying composite materials to understand their physical properties. Here, we have studied magnetoelectric multiferroic composite of two types of multiferroic (types I and II) consisting of BiFeO3 and TbMnO3 for enhanced magnetic and transport properties. The band structure was investigated with the help of UV–visible absorption spectrum, the valence band X-ray photoemission spectra (XPS), and ultraviolet photoemission spectra. The band structure thus obtained can successfully explain the magnetic and transport properties of the composite. The insulating behavior of the system is understood from the reconstruction of the energy bands at the interface and subsequent decrease in the band gap which happens due to lattice mismatch of the two materials. The large coercivity and the increase in the magnetization value are understood to be due to superexchange interaction between different Mn ions (Mn2+, Mn3+, and Mn4+). From the composition study of EDXA and core-level XPS, oxygen vacancy was found which in turn creates the mixed valence state of Mn to maintain the charge neutrality.