Li J, Chu H F, Zhang Y, Wang J, Zheng D N, Song Q, Wang P, Ma Y G, Ong C K, Wang S J
National Laboratory for Superconductivity, Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100080, People's Republic of China.
J Phys Condens Matter. 2009 Jul 8;21(27):276002. doi: 10.1088/0953-8984/21/27/276002. Epub 2009 Jun 10.
Epitaxial heterostructures of CoFe(2)O(4)/LaTiO(3)/LaAlO(3) have been successfully prepared by using the pulsed laser deposition technique. The magnetoresistance (MR) of the samples is negative and linear with field at H≥2 T, exhibiting no dependence on field directions. Nevertheless, when H<2 T, the MR is negative in a field parallel to the sample plane, but positive in that along the film normal. This novel observed anisotropic MR is explained in terms of the magnetic anisotropy in the ferrimagnetic layer, as well as the magnetoelastic coupling between the two. In fields of different directions, the top CoFe(2)O(4) layer contracts or expands in the sample plane due to the significant magnetostriction effect, changing its resistance accordingly and exerting compressive or tensile strains on the bottom LaTiO(3) layer. Apparently the orbital status and the one-electron bandwidth in the LaTiO(3) layer are altered, which leads to a change in resistance.
利用脉冲激光沉积技术成功制备了CoFe(2)O(4)/LaTiO(3)/LaAlO(3)外延异质结构。当H≥2 T时，样品的磁电阻（MR）为负且与磁场呈线性关系，与磁场方向无关。然而，当H<2 T时，在平行于样品平面的磁场中MR为负，而在沿薄膜法线方向的磁场中MR为正。这种新观察到的各向异性磁电阻是根据亚铁磁层中的磁各向异性以及两者之间的磁弹性耦合来解释的。在不同方向的磁场中，由于显著的磁致伸缩效应，顶部的CoFe(2)O(4)层在样品平面内收缩或膨胀，相应地改变其电阻，并对底部的LaTiO(3)层施加压缩或拉伸应变。显然，LaTiO(3)层中的轨道状态和单电子带宽发生了改变，从而导致电阻变化。
