5at%Mn-doped and undoped BaTiO3 thin films were grown under different oxygen partial pressures by pulsed laser deposition on platinum-coated sapphire substrates. X-ray diffraction measurements for all the thin films reveal a similar polycrystalline single-phase perovskite structure. Ferroelectricity was observed in the Mn-doped and undoped BaTiO3 thin films grown under relatively high oxygen partial pressure. Ferromagnetic coupling of the Mn dopant ions, on the other hand, was only seen in Mn-doped BaTiO3 thin films prepared under low oxygen partial pressure in a wide temperature range from 5 to 300K, and was attributed to the enhanced exchange coupling between Mn dopants and electrons at oxygen vacancies. The results showed that the leakage current was decreased with the doped Mn, but increases the dielectric loss and decreases the dielectric constant, and the ferroelectricity was impaired. To produce ferromagnetism, oxygen vacancies were necessary, which unfortunately increase the leakage current. This confirms that the mutual interplay between the ferroelectricity and ferromagnetism can be tuned by exchange coupling of the doped-Mn and oxygen vacancies in the BaTiO3 thin films.

The Coexistence of Ferroelectricity and Ferromagnetism in Mn-Doped BaTiO3 Thin Films. B.F.Ding, S.Q.Zhou: Chinese Physics B, 2011, 20[12], 127701