Manipulating magnetic anisotropy and ultrafast spin dynamics of magnetic nanostructures

Author: Zhao-Hua Cheng   Wei He   Xiang-Qun Zhang   Da-Li Sun   Hai-Feng Du   Qiong Wu   Jun Ye   Ya-Peng Fang   Hao-Liang Liu  

Publisher: IOP Publishing

E-ISSN: 1741-4199|24|7|77505-77524

ISSN: 1674-1056

Source: Chinese Physics B, Vol.24, Iss.7, 2015-07, pp. : 77505-77524

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Abstract

We present our extensive research into magnetic anisotropy. We tuned the terrace width of Si(111) substrate by a novel method: varying the direction of heating current and consequently manipulating the magnetic anisotropy of magnetic structures on the stepped substrate by decorating its atomic steps. Laser-induced ultrafast demagnetization of a CoFeB/MgO/CoFeB magnetic tunneling junction was explored by the time-resolved magneto-optical Kerr effect (TR-MOKE) for both the parallel state (P state) and the antiparallel state (AP state) of the magnetizations between two magnetic layers. It was observed that the demagnetization time is shorter and the magnitude of demagnetization is larger in the AP state than those in the P state. These behaviors are attributed to the ultrafast spin transfer between two CoFeB layers via the tunneling of hot electrons through the MgO barrier. Our observation indicates that ultrafast demagnetization can be engineered by the hot electron tunneling current. This opens the door to manipulate the ultrafast spin current in magnetic tunneling junctions. Furthermore, an all-optical TR-MOKE technique provides the flexibility for exploring the nonlinear magnetization dynamics in ferromagnetic materials, especially with metallic materials.