Structure and magnetization reversal mechanism in L1₀ FePt films with perpendicular magnetic anisotropy

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• 作者：S.J. Zhang^a ; Jian-Guo Zheng^b ; Z. Shi^a ; ^c ; ^{shizhong@tongji.edu.cn} ; S.M. Zhou^a ; ^c ; L. Sun^d ; J. Du^e
• 关键词：L10 ordered FePt ; Magnetization reversal ; Microstructure ; Sputtering ; Micro-structural evolution ; Perpendicular recording media ; Transmission electron microscopy
• 刊名：Thin Solid Films
• 出版年：2012
• 期刊代码：78_00406090
• 类别：ph
• 出版时间：30 June, 2012
• 卷：520
• 期：17
• 页码：5746-5751
• 文件大小：975 K

摘要

A series of L1₀ Fe₆₃Pt₃₇ films with controlled thickness (t_FM) were deposited on MgO(100) substrates for microstructure and magnetization reversal mechanism study. X-ray diffraction measurements show that face-centered tetragonal (200) peak also exists in addition to face-centered tetragonal (002) one, and becomes weak for thick films. High resolution electron microscopy study reveals the existence of periodic misfit dislocations at the FePt/MgO interface and other types of defects such as twins and antiphase boundary inside the film. Out-of-plane initial magnetization shows a slow increase responding to the external magnetic field and then follows a steep increase. The out-of-plane coercivity H_C at room temperature decreases with increasing t_FM and increases when the angle 胃_H between the external magnetic field and the film normal direction increases. H_C at 胃_H = 0 changes as a linear function of temperature for individual samples and the slope decreases with increasing t_FM. In addition, magnetic viscosity measurements show that the fluctuation field at room temperature decreases with increasing t_FM. These phenomena indicate that the magnetization reversal in the L1₀ FePt films should be realized by the motion of weakly pinned domain wall and thus governed by the thermal activation model. The magnetization reversal thermal activation volume and corresponding energy increase with increasing t_FM, as a result of the interactions between domain walls and structural defects can be attributed to the sample microstructural characteristic evolution with t_FM.