物理学报2016，Vol.65Issue(12)：127802-1-127802-7,7.DOI:10.7498/aps.65.127802
C掺杂FePt铁磁薄膜光诱导超快退磁动力学研究∗
Demagnetization dynamics of C-dop ed FePt film
摘要
Abstract
Magneto-optical information storage has been a hot research subject for several years. FePt exhibits abundant physical properties and has received much attention as a candidate material. Its alloy film with perpendicular anisotropy and small grain size has important applications in magnetic recordings due to the large intrinsic magnetic anisotropy which ensures long-time thermal stability of nanometer sized bits. However, the large coercive field of FePt is a significant factor that hinders its application. As is well known, the magnetic anisotropy in FePt alloy can be precisely modulated by carbon-doping, and as a result, the coercive field of FePt film can be modified effectively with the carbon dopant. On the other hand, the microscopic mechanism of magnetic storage relies on the motion of spin system. Ultrashort femtosecond laser has been demonstrated to be a very effective tool to investigate the dynamical coupling among different degrees of freedom, such as electron, spin and lattice in a ferromagnetic film. The research on spin dynamics has become a new frontier of condensed matter physics, which is crucial for ultrafast magnetic recording materials. In this work, by using the time-resolved magneto-optical Kerr effect spectroscopy, we study the ultrafast spin dynamics of two FePt alloy films with different carbon dopants under the applied magnetic field along the film surface. The FePt alloy films with different carbon dopants are fabricated on silicon substrates by the sputtering method. The main experimental findings in this work are as follows. (i) The transient Kerr signal is linearly proportional to the magnetization with the magnetic field up to 0.8 T, while the transient reflectivity of the film is independent of the applied magnetic field. (ii) For FePt alloy films with different coercive fields, it is found that the demagnetization time of the film with smaller coercive field is significantly faster than that of the larger counterpart: the former shows 0.8 ps demagnetization time, and the latter has a magnitude of 1.2 ps. The demagnetization times for both soft and hard magnetic films are independent of the applied magnetic field. (iii) With ultrafast laser pulse radiation, we observe the propagation of acoustic phonon with a resonance frequency of∼49 GHz, and the frequency of the acoustic phonon is independent of the applied magnetic field. From the above, the spin dynamics of the samples shows strong correlation with carbon-doping. Our experimental findings are desired for basic research as well as for the design and development of novel magneto-optical devices.关键词
FePt-C合金薄膜/磁光Kerr效应/超快退磁Key words
FePt-C alloy film/magneto-optical Kerr effect/ultrafast demagnetization引用本文复制引用
潘群峰,张泽宇,王会真,林贤,金钻明,程振祥,马国宏..C掺杂FePt铁磁薄膜光诱导超快退磁动力学研究∗[J].物理学报,2016,65(12):127802-1-127802-7,7.基金项目
国家自然科学基金(批准号:11174195)、高等学校博士学科点专项科研基金(批准号:20123108110003)和上海市教委重点课题(批准号:14ZZ101)资助的课题.@@@@* Project supported by the National Natural Science Foundation of China (Grant No.11174195), the Specialized Research Fund for the Doctoral Programs of Higher Education of China (Grant No.20123108110003), and the Research Innovation Fund of the Shanghai Education Committee, China (Grant No.14ZZ101) （批准号:11174195）
