Preparation of Transparent Oxides With Ferromagnetic and Ferroelectric Properties at room temperature by Doping Mn and La

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In this research, we have investigated the mechanism of ferromagnetic behavior exhibiting high Curie temperatures observed for perovskite-type dielectric oxides ABO_3(A=Sr, Ba, Ca, Pb, B=Ti, Zr) doped with La-Mn. In addition, we discussed the possibility of electric field-controlled magnetism through the investigation of relationship between the ferromagnetic and dielectric properties. The obtained results are as follows;1. La-Mn doped ATiO_3 (A=Sr, Ba, Ca) ceramics are ferromagnetic at room temperature, exhibiting magnetizations proportional to the Mn amount. The magnitude of observed magnetization depends on the final sintering temperature, reduced rapidly above 1200℃ at which the sintering density becomes higher.2. The high-resolution TEM observation and EDX composition analysis showed that there is a Mn-rich crystalline region around the grain boundaries for some La-Mn : BaTiO_3 ceramics. In addition, small peaks indicative of the ferromagnetic phase (La, Ba) MnO_3 were detected for these ceramics with the doped amount of La and Mn increasing.These result indicated that the ferromagnetism observed at room temperature is possibly ascribed to precipitation of a small amount of ferromagnetic manganite into the dielectric matrix.3. The 1 mol. % La-Mn doped BaTio_3 ceramics exhibiting simultaneously large magnetization and ferroelectricity at room temperature have been successfully prepared for the first time.It was found that the spontaneous magnetization of 1 mol. % La-Mn doped BaTio_3 ceramics exhibits the reduction as large as 45% for the applied electric field of 1.3 KV/mm. This reduction of magnetization by the electric field is of achieved for the first time and open the door to the control of magnetic moment using electric field.