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Modification of Pt/Co/Pt film properties by ion irradiation

机译:通过离子辐照改性Pt / Co / Pt膜的性能

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We studied the structural modifications of a Pt/Co/Pt trilayer epitaxial film under Ga~+ 30-keV ion irradiation by means of classical molecular dynamics and Monte Carlo simulations. The semiclassical tight-binding second-moment approximation potential was adjusted to reproduce the enthalpies of formation, the lattice constants, and the order-disorder transition temperatures for Co-Pt alloys. We found that during irradiation, the sandwich-type Pt(fcc)/Co(hcp)/Pt(fcc) film structure underwent a transition to the new solid solution α-Co/Pt(fcc) phase. Our analysis of the short-range order indicates the formation, within a nanosecond time scale, of a homogeneous chemically disordered solution. The longer time-scale simulations employing a Monte Carlo algorithm demonstrated that the transition from the disordered phase to the ordered L1_0 and L1_2 phases was also possible but not significant for the changes in perpendicular magnetic anisotropy (PMA) observed experimentally. The strain analysis showed that the Co layer was under tensile strain in the lateral direction at the fluences of 1.5 × 10~(14)-3.5 × 10~(14) ions cm~(-2); this range of fluences corresponds to the appearance of PMA. This strain was induced in the initially relaxed hcp Co layer due to its partial transformation to the fcc phase and to the influence of atomic layers with larger lattice constants at upper/lower interfaces.
机译:通过经典的分子动力学和蒙特卡罗模拟研究了Ga〜+ 30-keV离子辐照下Pt / Co / Pt三层外延膜的结构修饰。调整了半经典紧密结合的第二矩近似势,以再现Co-Pt合金的形成焓,晶格常数和有序-无序转变温度。我们发现,在辐照过程中,夹心型Pt(fcc)/ Co(hcp)/ Pt(fcc)薄膜结构经历了向新固溶体α-Co/ Pt(fcc)相的转变。我们对短程有序分析表明,在一纳秒的时间范围内,形成了均匀的化学无序溶液。使用蒙特卡洛算法的较长时间尺度的仿真表明,从无序相到有序的L1_0和L1_2相的过渡也是可能的,但对于实验观察到的垂直磁各向异性(PMA)的变化并不重要。应变分析表明,Co层在1.5×10〜(14)-3.5×10〜(14)离子cm〜(-2)的通量下在横向受到拉伸应变。此注量范围对应于PMA的外观。该应变是在最初松弛的hcp Co层中引起的,这是由于其向fcc相的部分转变以及上/下界面处具有较大晶格常数的原子层的影响。

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