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Magnetic properties of multilayers with strong interlayer coupling and perpendicular magnetic anisotropy

具有强层间耦合和垂直磁各向异性的多层膜的磁性能

基本信息

批准号：
15560571
负责人：
KITA Eiji
金额：
$ 2.3万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

项目摘要

We have investigated magnetic properties of multilayers which have both interlayer magnetic coupling and magnetic anisotropy. These two characteristics have been widely studied because they are essential properties for application to modern magnetic devices in spin-electronics fields. Co/Rh and Co/Ir were selected for the research targets since these multilayers simultaneously posses strong interlayer magnetic coupling and magnetic anisotropy. Rh and Ir have similar chemical properties because they stands at the same raw in the periodic table, namely have similar environments with outermost d electrons and almost the same lattice parameters with fcc structures. Additionally, the lattice mismatch between Co and these elements are about 7 %, relatively large, however we can still expect epitaxial growth between Co and Rh, Ir. All of the elements can be grown in the fcc structure and various growth directions are able to realized, for example (001) and (111).The samples were made by using an MBE deposition system. To study the thickness dependence on magnetic properties, wedged layers of Co or Rh, Ir were deposited. Magnetization process was measured with a SQUID magnetometer. For Co/Rh(111) multilayres, perpendicular magnetic anisotropy was found in the films with Co layer thickness less than 12 Å. This anisotropy can be originated in local stress due to the lattice miss-match or lower symmetry at the surface. From the analysis of streak patterns in RHEED, we derived in-plane lattice parameters and estimated in-plane stress. We found the anisotropy was well reproduced by the magneto-elastic energy generated with in-plane stress. The magnetization process of (001) multilayers applying an external magnetic field perpendicular to the films shows higher salutation magnetic fields than the value expected from the demagnetization field. For this case, strong "negative" perpendicular anisotropy was found and also explainable with the same manner as the (111) case.

我们研究了既有层间磁耦合又有磁各向异性的多层膜的磁性。这两个特性已经被广泛研究，因为它们是在自旋电子学领域中应用于现代磁性器件的基本特性。由于Co/Rh和Co/Ir两种多层膜同时具有较强的层间磁耦合和磁各向异性，因此选择这两种多层膜作为研究对象。Rh和Ir具有相似的化学性质，这是因为它们在元素周期表中处于相同的原始位置，即具有相似的环境，具有最外层的d电子和几乎相同的fcc结构的晶格参数。此外，Co和这些元素之间的晶格失配约为7%，相对较大，但我们仍然可以期待Co和Rh，Ir之间的外延生长。所有的元素都可以在面心立方结构中生长，并且能够实现不同的生长方向，例如(001)和(111)。为了研究厚度与磁性能的关系，我们沉积了Co或Rh，Ir的楔形层。用SQUID磁强计测量了磁化过程。对于Co/Rh(111)多层膜，Co层厚度小于12Å的薄膜存在垂直磁各向异性。这种各向异性可能起源于局部应力，原因是晶格失配或表面对称性较低。通过对RHEED中条纹图案的分析，我们得到了面内晶格参数，并估算了面内应力。我们发现，面内应力产生的磁弹性能很好地再现了各向异性。在垂直于薄膜的外加磁场作用下，(001)多层膜的磁化过程显示出比退磁磁场预期值更高的跃迁磁场。对于这种情况，发现了强烈的“负”垂直各向异性，并且也可以用与(111)情况相同的方式来解释。