Creation of room-temperature-multiferroic oxides and electric-field-controlled magnetization

室温多铁氧化物的制备和电场控制磁化

基本信息

批准号：
16360151
负责人：
GOMI Manabu
金额：
$ 7.74万
依托单位：
Nagoya Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

New materials exhibiting a large magnetoelectric effect due to coexistence of ferromagnetism and ferroelectricity at room temperature have been investigated. The following research results are obtained ;1.Electric-field-induced magnetization reduction and the mechanism in oxides exhibiting simultaneously ferromagnetism and ferroelectrics.(1)Coexistence of ferromagnetism and ferroelectricity observed in La, Mn : BaTiO_3 and BaTiO_3-LaMnO_3 composites are due to a small amount of ferromagnetic (La, Ba)MnO_3 phase precipitated into the grain boundaries or the inside of the ferroelectric grains.(2)The composites BaTiO_3-LaMnO_3 are materials simultaneously exhibiting ferroelectricity and a relatively ferromagnetic magnetization at room temperature. The density and dielectric properties of the composites markedly improved with the grain size of LaMnO_3 decreasing. When an electric field of 750 V/mm was applied to the composites, magnetization reduction as large as 25 % was observed for the … More first time.(3)An electric-field-induced magnetization reduction similar to that in the composites was observed for BaTiO_3/BaTiO_3-LaMnO_3 composite / BaTiO_3 structures where a composite was sandwiched between ferroelectric insulator BaTiO_3 layers. This suggests that the observed magnetization reduction is probably not due to thermal effect but intrinsic field-induced effect. Change of hole concentration in (La, Ba)MnO_3 induced by the dielectric polarization may be responsible for the magnetization reduction.(4)An electric-field-induced magnetization reduction of 2.2 % for the applied voltage of 4V was observed in a BaTiO_3/(La, Ba)MnO_3/BaTiO_3 layer structure. This is direct evidence showing the magnetization change to originate from the induced polarization.2.Search for new multiferroic materials(1)Pb(Zr, Ti)O_3-LaMnO_3 composites are new multiferroics with higher ferroelectric Curie temperature and larger polarization than BaTiO_3 system. It has been found for the first time that they exhibits a magnetization reduction as large as 30 % for a low applied electric field of 0.4 kV/mm at room temperature. Less

研究了室温下铁磁性和铁电性共存而表现出大磁电效应的新材料，取得了以下研究成果：1.同时表现出铁磁性和铁电性的氧化物中电场诱导磁化强度的降低及其机理。(1) )在La、Mn:BaTiO_3和中观察到铁磁性和铁电性的共存BaTiO_3-LaMnO_3复合材料是由于在晶界或铁电晶粒内部析出少量铁磁(La,Ba)MnO_3相而形成的。(2)BaTiO_3-LaMnO_3复合材料是同时表现出铁电性和相对铁磁磁化强度的材料。在室温下，复合材料的密度和介电性能随着晶粒尺寸的增加而显着提高。当对复合材料施加 750 V/mm 的电场时，首次观察到磁化强度降低了 25%。(3) 电场引起的磁化强度降低与观察到BaTiO_3/BaTiO_3-LaMnO_3复合材料/BaTiO_3结构的复合材料，其中复合材料夹在铁电绝缘体BaTiO_3层之间。表明观察到的磁化强度降低可能不是由于热效应，而是由介电极化引起的(La, Ba)MnO_3 中的空穴浓度变化导致磁化强度降低。(4)电-在 BaTiO_3/(La, Ba)MnO_3/BaTiO_3 层结构中观察到施加 4V 电压时场致磁化强度降低 2.2%，这是表明磁化强度变化的直接证据。 2.寻找新型多铁材料(1)Pb(Zr,Ti)O_3-LaMnO_3复合材料是首次发现比BaTiO_3体系具有更高铁电居里温度和更大极化强度的新型多铁材料。在室温下，对于 0.4 kV/mm 的低外加电场，它们的磁化强度降低高达 30%。