Absence of ferromagnetism in ferroelectric Mn-doped BaTiO3 nanofibers

Pure and Mn-doped barium titanate nanofibers were synthesized by the electrospinning method. The morphology, microstructure and crystal structure of as-spun and annealed composite nanofibers were characterized by scanning electron microscopy and transmission electron microscopy. After annealing at 850 degrees C, we obtain nanofibers a few mu m long, formed by nanoparticles of irregular shape with sizes around 100 nm. X-ray diffraction and Raman spectroscopy show that a partial phase transition from tetragonal to hexagonal takes place for BaTi0.90Mn0.10O3. Vibrational phonon modes were calculated for BaTiO3 within the density functional theory (DFT) framework. Ferroelectricity has been probed on pure and Mn-doped BaTiO3 nanofibers, by means of piezoresponse force microscopy in an atomic force microscope, confirming the polar domain switching behavior of the fibers. The measured piezoelectric coefficient d(33) were 31 and 22 pm/V for BaTiO3 and BaTi0.90Mn0.10O3. Magnetic properties of the samples were probed in a superconducting quantum interference device. Diamagnetic and paramagnetic behaviors were found in pure and Mn-doped samples, respectively.