| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2003: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2002: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Research Abstract |
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.
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