Tunable Multifunctionalities in BaTiO3–La0.835Na0.165MnO3 Composites: From UV to Visible Absorption and Nonmagnetic to Room-Temperature Ferromagnetism

Abstract

The composites of ferroelectric BaTiO₃ and ferromagnetic La_0.835Na_0.165MnO₃ viz. (1-x) BaTiO₃ : (x) La_0.835Na_0.165MnO₃, x=0, 10, 20, 30, 50, 100 (in %) were prepared using conventional solid-state reaction method. The work investigates the effect of magnetic inclusion in a nonmagnetic matrix. The synthesized nonmagnetic BaTiO₃ has majorly crystalized in ferroelectric tetragonal structure of P4mm space group and magnetic inclusion La_0.835Na_0.165MnO₃ has shown phase segregation into rhombohedral lattice belonging to R3 @#x0305;c space group and monoclinic lattice belonging to deficient La_0.9MnO₃ like structure of space group I 1 2/a 1. The composites so formed are immiscible solid solutions of Ti-deficient BaTiO₃ and A-site deficient La_0.835Na_0.165MnO₃. The BaTiO₃ and La_0.835Na_0.165MnO₃ are morphologically distinct with contrasting grain size and distribution. Composites show loosely bound immiscible grain distribution. The mixing of a nonmagnetic insulator and a ferromagnetic metal/semiconductor has given composites a unique optical attribute. The band gap has been effectively tuned to visible region of the electromagnetic spectra from ultraviolet wavelengths. The composites possess large Urbach energy. BaTiO₃ in its non-stoichiometric form is found to be a weak ferromagnet at room temperature with spin-glass like frustration at the low measurable temperatures. The La_0.835Na_0.165MnO₃ has shown double magnetic transition due to structural phase segregation. The composites show robust ferromagnetism at room temperature inheriting it from magnetic counterpart La_0.835Na_0.165MnO₃. The salient ferroelectricity of BaTiO₃ has disappeared in composites due to large leakage currents. But at low bias voltages, leaky ferroelectric nature with ferromagnetism does exist at room temperature in x=10% specimen, making it photosensitive multiferroic magnetoelectric composite oxide for room temperature applications.