Ultrafast laser induced magnetization reversal in L10 FePt films with different chemical orders
J. Y. Shi,
X. F. Hu,
M. Tang,
J. Xu,
L. Q. Shen,
S. M. Zhou,
X. J. Yang,
Y. Z. Wu,
L. Y. Chen,
H. B. Zhao
Affiliations
J. Y. Shi
Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), and Shanghai Ultra-Precision Optical Manufacturing Engineering Research Center, Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China
X. F. Hu
Department of Physics, State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
M. Tang
Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
J. Xu
Department of Physics, State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
L. Q. Shen
Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), and Shanghai Ultra-Precision Optical Manufacturing Engineering Research Center, Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China
S. M. Zhou
Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
X. J. Yang
Department of Physics, State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
Y. Z. Wu
Department of Physics, State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
L. Y. Chen
Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), and Shanghai Ultra-Precision Optical Manufacturing Engineering Research Center, Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China
H. B. Zhao
Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), and Shanghai Ultra-Precision Optical Manufacturing Engineering Research Center, Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China
Using an ultrafast laser pulse as a substitution of continuous-wave laser to excite a magnetic film leads to high spin temperature and fast demagnetization, beneficial to the rapid and efficient photo-assisted magnetization (M) reversal. Here, ultrafast laser induced M reversal in perpendicular magnetic anisotropy L10 FePt films with different chemical ordering parameter (from S0.9) was investigated using magneto-optical Kerr effect (MOKE). It was found that the coercive field (Hc) without laser excitation increases from ∼0.8 to ∼4 kOe with increasing S, but Hc becomes smaller for enhanced laser fluence (F) and reaches an analogous small value of ∼0.2 kOe for F>12 mJ cm-2. Despite such a significant softening in films with high S, the laser induced M reversal rate is slightly less than 1 even for the applied field (H) much larger than 0.2 kOe. This reveals a small portion of spins are photo inactively pinned, as confirmed by magnetic force microscopy measurements. Such pinning sites may be reduced with improved chemical order and morphology. We also found an approximately inverse linear relation between the H and the corresponding threshold F to induce the M reversal in the film of high S, which can be described by an ultrafast thermal activated spin flip model.
