Structure and property changes and femtosecond laser-induced magnetization dynamics of two-year-old high coercive TbFeCo films

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• 作者：Chudong Xu^a ; ^c ; ^{cd79cd@126.com} ; Zhifeng Chen^a ; Xu Yang^a ; Shufa Li^a ; Daxin Chen^a ; Shiming Zhou^b ; ^{shiming@tongji.edu.cn} ; Tianshu Lai^a ; ^{stslts@mail.sysu.edu.cn}
• 关键词：TbFeCo ; bilayer structure ; Magneto-optical property ; Magnetization dynamics
• 刊名：Journal of Magnetism and Magnetic Materials
• 出版年：2012
• 期刊代码：31_03048853
• 类别：ph
• 出版时间：July, 2012
• 卷：324
• 期：13
• 页码：2034-2038
• 文件大小：491 K

摘要

An uncoated TbFeCo film on glass substrate exposed to dry air for 2 years is studied using magneto-optical polar Kerr spectroscopy and vibrating sample magnetometry (VSM). The out-of-plane hysteresis loop by VSM is found to become slanted and meanwhile, an in-plane loop is also observable. The Kerr loop measured from the exposed surface is also slanted compared to that measured from the substrate-contacted surface, which indicates that the exposed surface is oxidized. So a bilayer structure of the film is proposed. When a pump laser is switched on, the Kerr loops measured from both surfaces at the delay time of 鈭? ps become anomalous, showing the occurrence of magnetization reversal across magnetization compensation temperature. Unlike that measured from the substrate-contacted surface, femtosecond laser-induced magnetization dynamics measured from the exposed surface does not show magnetization reversal crossing zero magnetization. This can be explained by the bilayer structure as the compensation effect of demagnetization recovery of the oxidized layer on magnetization reversal of perpendicularly anisotropic TbFeCo layer across magnetization compensation temperature. Above experimental results show that the uncoated TbFeCo film cannot resist oxidation in dry air at room temperature for 2 years while the SiO₂-coated surface can do so for over 2 years.