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Tb/FeCo多层膜的垂直交换偏置效应

Perpendicular Exchange Bias Effect in Tb/FeCo Multilayer Films

  • 摘要: 采用磁控溅射方法,制备结构为Glass/Cu(60 nm)/Tb(tTb=1.5,3.0 nm)/FeCo(1.5 nm)5/Ta(10 nm)的两种不同Tb子层厚度的多层膜。采用X射线衍射分析仪、原子力和磁力显微镜、振动样品磁强计对样品的晶体结构、磁畴结构和室温磁性质进行表征,研究该多层膜系统的垂直磁各向异性和垂直交换偏置效应。X射线衍射分析表明,多层膜中Tb/FeCo界面主要呈非晶或纳米晶态。磁力显微镜结果显示,制备态薄膜均呈现迷宫状条纹磁畴结构。室温磁性测量表明,薄膜的易磁化方向都垂直膜面,垂直矫顽力分别为122和351 kA/m。在由这两种多层膜组合而成的Glass/Cu(60 nm)/Tb(1.5 nm)/FeCo(1.5 nm)2/Tb(3.0 nm)/FeCo(1.5 nm)5/Ta(10 nm)软磁/硬磁型多层膜中发现交换偏置场为20 kA/m的垂直交换偏置效应,这一效应的发现对Tb/FeCo多层膜在现代超快磁存储器中的应用具有重要意义。

     

    Abstract: Two kinds of Glass/Cu(60 nm)/Tb(tTb=1.5, 3.0 nm)/FeCo(1.5 nm)5/Ta(10 nm) multilayer films were fabricated by magnetron sputtering method. The crystal structure, magnetic domain structure and room temperature (RT) magnetic properties of the samples were characterized with X-ray diffraction, atomic force and magnetic force microscopy, and vibrating sample magne-mtoeter. The perpendicular magnetic anisotropy and perpendicular exchange bias effects of the multilayer films were studied. X-ray diffraction analysis show that the Tb/FeCo interfaces in the multilayer films are mainly in amorphous or nanocrystalline structure. The magnetic force microscope images exhibit a disordered labyrinthine stripe domain structure for all of the as-deposited films. The magnetic measurements at RT show that all the samples exhibit out-of-plane anisotropy with the perpendicular coercive fields of 122 and 351 kA/m for the Glass/Cu(60 nm)/Tb(tTb)/FeCo(1.5 nm)5/Ta(10 nm) multilayers with tTb=1.5 and 3.0 nm, respectively. A robust perpendicular exchange bias (P-EB) effect with an exchange bias field of 20 kA/m is observed in a prototypical soft/hard exchange coupled spin valve structure consisting of Glass/Cu(60 nm)/Tb(1.5 nm)/FeCo(1.5 nm)2/Tb(3.0 nm)/FeCo(1.5 nm)5/Ta(10 nm) multilayers. Such a robust P-EB effect obtained in Tb/FeCo based multilayer films may be of crucial importance for applications in modern ultrafast storage media.

     

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