Abstract

The possibility of using implantation of 20-keV He⁺ ions for modification of the domain structure and magnetic properties of CoPt films (formed by the electron-beam evaporation method) with different cobalt contents (Co_0.45Pt_0.55 and Co_0.35Pt_0.65) has been investigated. A decrease in the coercive field (narrowing of the hysteresis loop in the magnetic-field dependences of the Faraday angle and magnetization) with an increase in the He⁺ ion fluence from 2 × 10¹⁴ to 4 × 10¹⁴ cm^–2 has been found for the irradiated CoPt samples of both compositions. The residual magnetization of the Co_0.35Pt_0.65 films coincides with the saturation magnetization, and a decrease in the residual magnetization is observed for Co_0.45Pt_0.55. It is shown by magnetic force microscopy that the largest number of round isolated domains (skyrmions) for the Co_0.45Pt_0.55 alloy are formed when the ion fluence increases to 3 × 10¹⁴ cm^–2, while 360-degree domain walls (1D skyrmions) are observed along with round isolated domains for the Co_0.35Pt_0.65 films irradiated with a He⁺ fluence of 4 × 10¹⁴ cm^–2. An analysis of CoPt films by Mandelstam–Brillouin spectroscopy revealed an increase in the shift between the Stokes and anti-Stokes components of the spectrum and a significant enhancement of the Dzyaloshinski–Moriya interaction in the irradiated samples. Model calculations performed using the SRIM program showed that the ion irradiation facilitates asymmetric mixing of Co and Pt atoms in CoPt films, which may underlie the mechanism of the observed effects of ion irradiation on their magnetic properties and domain structure.

中文翻译：

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离子辐照对CoPt薄膜磁性能的影响

摘要

使用20keV He ⁺离子注入来改变钴含量（Co _0.45 Pt _0.55和Co _0.35 Pt _0.65）的CoPt膜（通过电子束蒸发法形成）的畴结构和磁性能的可能性被调查了。已经发现，随着He ⁺离子通量从2×10 ¹⁴增大到4×10 ¹⁴ cm ^–2，矫顽场减小（磁滞回线在法拉第角和磁化强度的磁场依赖性中变窄）减小。两种成分的辐照CoPt样品。Co _0.35的剩余磁化强度Pt _0.65膜与饱和磁化强度一致，并且对于Co _0.45 Pt _0.55观察到剩余磁化强度降低。磁力显微镜显示，当离子通量增加到3×10 ¹⁴ cm ^–2时，形成的Co _0.45 Pt _0.55合金的最大圆形隔离域（天空离子）形成，而360度畴壁（一维天空离子）形成）以及伴随着He ⁺通量为4×10 ¹⁴ cm ^–2的Co _0.35 Pt _0.65薄膜的圆形隔离区域。通过Mandelstam–Brillouin光谱分析CoPt薄膜，发现光谱的斯托克斯和反斯托克斯分量之间的偏移增加，并且辐照样品中的Dzyaloshinski–Moriya相互作用显着增强。使用SRIM程序进行的模型计算表明，离子辐照有助于CoPt膜中Co和Pt原子的不对称混合，这可能是观察到的离子辐照对其磁性能和畴结构影响的机理。