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Development of new recyclable materials based on iron oxides for nano-devices

开发用于纳米器件的基于氧化铁的新型可回收材料

基本信息

批准号：
14350353
负责人：
FUJII Tatsuo
金额：
$ 9.54万
依托单位：
OKAYAMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

To develop new spintronics materials with environment friendly, we prepared well-crystallized epitaxial Fe_<1.2>Ti_<0.8>O_3 films which had the largest magnetization within the hematite (α-Fe_2O_3)-ilmenite (FeTiO_3) solid solution system. The films were prepared by reactive sputtering technique with an FeTi alloy target. The precise control of substrate temperature and oxygen pressure during sputtering was necessary to obtain ferromagnetic films with R^^- symmetry, in which Fe-rich and Ti-rich layers alternately stacked along the c-axis.By the way it is well known that the exchange coupling between two magnetic layers influence the magnetic properties of adjacent layers. We prepared Fe_<1.2>Ti_<0.8>O_3/Fe_2O_3 bilayered films and measured the magnetic Curie temperature (T_c) of them. In spite of the higher substrate temperature of 550℃, the films had a sharp interface between layers. The T_c of bilayered films was about 220 K, which was a little higher than that (210 K) of Fe_<1.2>Ti_<0.8>O_3 single layered films. The strong magnetic coupling to the antiferromagnetic α-Fe_2O_3 layer, which had the high Neel temperature of 960 K, could increase the T_c of the Fe_<1.2>Ti_<0.8>O_3 layer.The electronic structures of α-Fe_2O_3-FeTiO_3 are generally considered as the mixed valence states between Fe^<2+> and Fe^<3+> due to the substitution of Fe^<3+> for Ti^<4+>. The nominal valence states of Ti are fixed to 4+. However high-resolution X-ray fluorescence spectra of various titanium oxides suggested that the Ti Kα and Kβ peak profiles of FeTiO_3 were slightly different form those of other Ti^<4+> compounds and were better to assign to have some Ti^<3+> characters. Moreover the valence band spectra of FeTiO_3 by X-ray photoelectron spectroscopy had a small density just below the Fermi edge, probably assigned to the localized Ti 3d electron.

为了开发环境友好的新型自旋电子材料，我们制备了在赤铁矿(α-Fe_2O_3)-钛铁矿(FeTiO_3)固溶体体系中具有最大磁化强度的结晶良好的外延Fe_<1.2>Ti_<0.8>O_3薄膜。该薄膜采用 FeTi 合金靶材通过反应溅射技术制备。溅射过程中对衬底温度和氧气压力的精确控制对于获得具有R^^-对称性的铁磁薄膜是必要的，其中富Fe层和富Ti层沿c轴交替堆叠。众所周知，两个磁性层之间的交换耦合会影响相邻层的磁性能。我们制备了Fe_<1.2>Ti_<0.8>O_3/Fe_2O_3双层薄膜并测量了其磁居里温度(T_c)。尽管基底温度高达550℃，薄膜的层间界面仍清晰。双层薄膜的T_c约为220K，略高于Fe_1.2Ti_0.8O_3单层薄膜的T_c(210K)。对尼尔温度高达960 K的反铁磁α-Fe_2O_3层的强磁耦合可以提高Fe_<1.2>Ti_<0.8>O_3层的T_c。由于 Fe^<3+> 对应 Ti^<4+>。 Ti 的标称价态固定为 4+。然而，各种钛氧化物的高分辨率X射线荧光光谱表明，FeTiO_3的Ti Kα和Kβ峰形与其他Ti^<4+>化合物的Ti Kα和Kβ峰形略有不同，并且更容易归因于具有某些Ti^<3+>特征。此外，X射线光电子能谱显示FeTiO_3的价带谱在费米边下方有一个小密度，可能归因于局域Ti 3d电子。