On the relationship of magnetocrystalline anisotropy and stoichiometry in epitaxial L10 CoPt (001) and FePt (001) thin films -: art. no. 033904
On the relationship of magnetocrystalline anisotropy and stoichiometry in epitaxial L10 CoPt (001) and FePt (001) thin films -: art. no. 033904
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DOI：
10.1063/1.1991968
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发表时间：
2005-08-01
影响因子：
3.2
通讯作者：
Thiele, JU
中科院分区：
文献类型：
--
作者：
Barmak, K;Kim, J;Thiele, JU
通过溅射到单晶 MgO(001) 基底上制备了标称厚度为 42 或 50 nm 的两个系列的外延 CoPt 和 FePt 薄膜，以研究化学有序性和所得磁性能随合金成分的变化。在第一个系列中，薄膜成分保持恒定，而基底温度从 144 摄氏度增加到 704 摄氏度。在第二个系列中，CoPt 的基底温度保持在 704 摄氏度，FePt 的基底温度保持在 620 摄氏度，而合金化学计量在 40-60 at 的标称范围内变化。 ％钴（铁）。通过卢瑟福背散射光谱法测量薄膜成分和厚度。使用 X 射线衍射获得了两组薄膜的 L1(0) 相的晶格和长程有序参数。使用扭矩磁力测定法确定了一部分薄膜的室温磁晶各向异性常数。研究发现有序参数随着温度的升高而增加，与 CoPt 相比，FePt 更容易发生有序化。当基底温度高于 534 摄氏度时，CoPt 中会产生垂直各向异性，而 FePt 中则在高于 321 摄氏度时会产生垂直各向异性。通过磁力显微镜观察，CoPt 和 FePt 中磁畴的结构和宽度也表明磁各向异性随着温度的升高而增加。对于在最高温度下沉积的薄膜（CoPt为704℃，FePt为620℃），有序参数在等原子组成附近达到最大值，而磁晶各向异性随着Co或Fe浓度从低于等原子组成增加到略高于等原子组成而增加。结论是，Co 或 Fe 稍微过量的非化学计量 L1(0) CoPt 和 FePt 对于需要最高各向异性的应用来说是优选的。 (c) 2005 年美国物理研究所。
Two series of epitaxial CoPt and FePt films, with nominal thicknesses of 42 or 50 nm, were prepared by sputtering onto single-crystal MgO(001) substrates in order to investigate the chemical ordering and the resultant magnetic properties as a function of alloy composition. In the first series, the film composition was kept constant, while the substrate temperature was increased from 144 to 704 degrees C. In the second series the substrate temperature was kept constant at 704 degrees C for CoPt and 620 degrees C for FePt, while the alloy stoichiometry was varied in the nominal range of 40-60-at. % Co(Fe). Film compositions and thicknesses were measured via Rutherford backscattering spectrometry. The lattice and long-range order parameter for the L1(0) phase were obtained for both sets of films using x-ray diffraction. The room-temperature magnetocrystalline anisotropy constants were determined for a subset of the films using torque magnetometry. The order parameter was found to increase with increasing temperature, with ordering occurring more readily in FePt when compared with CoPt. A perpendicular anisotropy developed in CoPt for substrate temperatures above 534 degrees C and in FePt above 321 degrees C. The structure and width of the magnetic domains in CoPt and FePt, as seen by magnetic force microscopy, also demonstrated an increase in magnetic anisotropy with increasing temperature. For the films deposited at the highest temperatures (704 degrees C for CoPt and 620 degrees C for FePt), the order parameter reached a maximum near the equiatomic composition, whereas the magnetocrystalline anisotropy increased as the concentration of Co or Fe was increased from below to slightly above the equiatomic composition. It is concluded that nonstoichiometric L1(0) CoPt and FePt, with a slight excess of Co or Fe, are preferable for applications requiring the highest anisotropies. (c) 2005 American Institute of Physics.