Influences of annealing temperature on structural characterization and magnetic properties of Mn-doped BaTiO3 ceramics

Polycrystalline samples of BaTiO3 doped with 2.0 at.% Mn were prepared by solid-state reaction at various temperatures (T-an) ranging from 500 to 1350 degrees C, used high-pure powders of BaCO3, TiO2, and MnCO3 as precursors. Experimental results obtained from x-ray diffraction patterns and Raman scattering spectra reveal that tetragonal Mn-doped BaTiO3 starts constituting as T-an approximate to 500 degrees C. The T-an increase leads to the development of this phase. Interestingly, there is the tetragonal-hexagonal transformation in the crystal structure of BaTiO3 as T-an approximate to 1100 degrees C. Such the variations influence directly magnetic properties of the samples. Besides paramagnetic contributions of Mn2+ centers traced to electron spin resonance, the room-temperature ferromagnetism found in the samples is assigned to exchange interactions taking place between Mn3+ and Mn4+ ions located in tetragonal BaTiO3 crystals. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4733691]