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

在本研究中，我们研究了钙钛矿型介电氧化物ABO_3（A=Sr, Ba, Ca, Pb， B=Ti, Zr）掺杂La-Mn的高居里温度下铁磁行为的机理。此外，通过对铁磁性和介电性质关系的研究，讨论了电场控磁的可能性。得到的结果如下：1。掺La-Mn的ATiO_3 （A=Sr, Ba, Ca）陶瓷在室温下具有铁磁性，其磁化强度与Mn量成正比。观察到的磁化强度取决于最终烧结温度，在1200℃以上迅速降低，烧结密度变得更高。高分辨率TEM观察和EDX成分分析表明，某些La-Mn: BaTiO_3陶瓷在晶界周围存在富mn晶区。此外，随着La和Mn掺杂量的增加，陶瓷中出现了小的铁磁相（La, Ba） MnO_3。这些结果表明，在室温下观察到的铁磁性可能是由于少量铁磁性锰矿析出到介电基质中。首次成功制备了1 mol. % La-Mn掺杂的BaTio_3陶瓷，在室温下同时具有高磁化强度和铁电性。结果表明，1 mol. % La-Mn掺杂的BaTio_3陶瓷在1.3 KV/mm的电场作用下，自发磁化强度降低了45%。这是首次实现了电场磁化强度的降低，为利用电场控制磁矩打开了大门。

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.