Self assembled nanoscale structure - super sensitive tunneling magnetoresisitance effect of dielectric and ferromagnetic hybrid structure

颗粒状磁性复合薄膜，其中纳米级铁磁性金属颗粒（如Co）分散在绝缘体基体（如Sm_20_3）中，是电子应用的有吸引力的材料，因为薄膜的额外自由度（如颗粒尺寸和金属体积分数）使我们能够为应用制造定制的介质。特别是，这些薄膜所表现出的大隧道型磁阻（TMR）效应，对于构建各种电子应用的磁头和传感器是有用的；磁软薄膜的TMR效应变得不可或缺。在本报告中，我们证明了采用FeNi斜溅射薄膜作为颗粒膜的底层，可以显著改善Co-Sm-0薄膜电阻率变化的低场响应。采用射频磁控溅射装置制备薄膜。衬底被放置在铜楔上，倾角θ=60°固定在阴极上。斜阴极下射频磁控溅射制备了具有纳米结构的铁磁性薄膜…More （Fe, Co， Ni和Fe_<20>Ni_<80>）。斜溅射有效地形成了自组织的纳米级波纹结构，其平均高度和间距约为10 nm。由于形状效应，所得薄膜明显表现出单轴面内磁各向异性，但易轴的大小和方向在不同样品之间发生变化，这在很大程度上取决于材料和薄膜厚度（沉积时间）。除了形状效应外，晶体磁性各向异性对纳米级磁性结构的单轴各向异性的形成也起着重要作用。使用斜溅射FeNi薄膜的堆肥薄膜下层受到后离子铣削蚀刻。将Co_<76>(Sm_20_3)_<24> (f_v=52vol.%)厚度为43 nm的颗粒膜直接沉积在平均厚度为20 nm的FeNi斜溅射沉积膜上。由于相邻FeNi纳米级波纹结构间隙中的杂散场，复合薄膜表现出相当大的软磁特性。薄膜的磁软化提高了低场TMR响应，在500e的小场下，薄膜的Δp/p_0（p_0=2.9X10^5μΩcm）值达到3%以上。由此得出，复合膜的场灵敏度Δp/p_o比Co-Sm-0单层膜高约240倍，表明斜溅射FeNi底层膜的有效性。少

Granular magnetic composite films, in which nano-scale ferromagnetic metal particles such as Co are dispersed in insulator matrices such as Sm_20_3, are attractive materials for electronic applications, because the extra degrees of freedom (e. g. granule size and metal volume fraction) of films enable us to fabricate tailored media for applications. Especially, the large tunneling-type magnetoresistance (TMR) effect that these films exhibit is useful for constructing magnetic heads and sensors for various electronic applications ; magnetically soft TMR effect of films becomes indispensable. In this report, we demonstrate that the low field response of the resistivity change of Co-Sm-0 films can be improved considerably by employing FeNi obliquely sputtered films as the underlayer of the granular films.Films were prepared by using a rf-magnetron sputtering apparatus. The substrate was placed on a copper wedge with inclination angle θ=60deg fixed to the cathode. Ferromagnetic thin films … More (Fe, Co, Ni and Fe_<20>Ni_<80>) with nano-scale structures were formed by RF magnetron sputtering under oblique cathode arrangements. The oblique sputtering was effective to form self-organizing like nano-scale corrugate structures whose average height and spacing were approximately 10 nm. The resultant films clearly exhibited uniaxial inplane magnetic anisotropy due to the shape effect, but the magnitude and the direction of easy axis changed from sample to sample depending strongly on the material and the film thickness (deposition time). Beside the shape effect, crystalline magnetic anisotropy also plays an important role for the formation of uniaxial anisotropy of the nano-scale magnetic structures.An underlayer of composted film used an obliquely sputtered FeNi films were subject to post ion-milling etching. Then, The Co_<76>(Sm_20_3)_<24> (f_v=52vol.%) granular film with 43 nm thickness was directly deposited onto the FeNi obliquely sputter deposited film with the average thickness of 20 nm. The composite film exhibited a considerably soft magnetization due to the stray field in gaps between neighboring FeNi nano-scale corrugate structures. The magnetic softening of film yielded the improvement of low field TMR response : with a small field of 500e, the Δp/p_0(p_0=2.9X10^5μΩcm) value of film reached more than 3 %. From this value, the field sensitivity of Δp/p_o of the composite film is evaluated to be about 240 times higher than that of the Co-Sm-0 single-layer film, suggesting the effectiveness of the obliquely sputtered FeNi underlayer film. Less