Unikandanunni Vivek, Medapalli Rajasekhar, Asa Marco, Albisetti Edoardo, Petti Daniela, Bertacco Riccardo, Fullerton Eric E, Bonetti Stefano
Department of Physics, Stockholm University, 10691 Stockholm, Sweden.
Center for Memory and Recording Research, University of California San Diego, San Diego, California 92093, USA.
Phys Rev Lett. 2022 Dec 2;129(23):237201. doi: 10.1103/PhysRevLett.129.237201.
We investigate the spin dynamics driven by terahertz magnetic fields in epitaxial thin films of cobalt in its three crystalline phases. The terahertz magnetic field generates a torque on the magnetization which causes it to precess for about 1 ps, with a subpicosecond temporal lag from the driving force. Then, the magnetization undergoes natural damped THz oscillations at a frequency characteristic of the crystalline phase. We describe the experimental observations solving the inertial Landau-Lifshitz-Gilbert equation. Using the results from the relativistic theory of magnetic inertia, we find that the angular momentum relaxation time η is the only material parameter needed to describe all the experimental evidence. Our experiments suggest a proportionality between η and the strength of the magnetocrystalline anisotropy.
我们研究了钴的三种晶相外延薄膜中太赫兹磁场驱动的自旋动力学。太赫兹磁场在磁化强度上产生一个转矩，使其进动约1皮秒，相对于驱动力存在亚皮秒的时间延迟。然后，磁化强度以晶相特征频率进行自然阻尼太赫兹振荡。我们通过求解惯性朗道 - 里夫希茨 - 吉尔伯特方程来描述实验观测结果。利用磁惯性相对论理论的结果，我们发现角动量弛豫时间η是描述所有实验证据所需的唯一材料参数。我们的实验表明η与磁晶各向异性强度之间存在比例关系。
