Precession damping in [Co60Fe40/Pt]5 multilayers with varying magnetic homogeneity investigated with femtosecond laser pulses
We report on the ultrafast magnetization dynamics of [Co60Fe40/Pt]5 multilayers studied with femtosecond laser pulses. The samples were grown at room temperature by DC magnetron sputtering with Ta capping and Pt buffer layers and present the same thickness and perpendicular magnetic anisotropy as de...
| Autores: | , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2019 |
| País: | Brasil |
| Institución: | Universidade Federal de Minas Gerais (UFMG) |
| Repositorio: | Repositório Institucional da UFMG |
| Idioma: | inglés |
| OAI Identifier: | oai:repositorio.ufmg.br:1843/80456 |
| Acceso en línea: | https://doi.org/10.1063/1.5130458 http://hdl.handle.net/1843/80456 https://orcid.org/0000-0001-9857-3373 https://orcid.org/0000-0001-6600-6921 https://orcid.org/0000-0003-4010-8043 https://orcid.org/0000-0002-2869-6092 https://orcid.org/0000-0003-3264-337X https://orcid.org/0000-0002-0507-2471 |
| Access Level: | acceso abierto |
| Palabra clave: | Magnetic anisotropy Magnetic materials Magnetic ordering Magnetization dynamics Spin pumping Magnetic force microscopy Magnetron sputtering Landau-Lifshitz-Gilbert equation Femtosecond lasers Photoexcitations Anisotropia Magnetismo |
| Sumario: | We report on the ultrafast magnetization dynamics of [Co60Fe40/Pt]5 multilayers studied with femtosecond laser pulses. The samples were grown at room temperature by DC magnetron sputtering with Ta capping and Pt buffer layers and present the same thickness and perpendicular magnetic anisotropy as determined by vibrating sample magnetometry. Controlled growth rate of the Pt buffer layer modified the anisotropy fields and magnetic domain sizes as measured by magnetic force microscopy (MFM). An estimation of the average magnetic domain sizes was obtained from the profile of the self-correlation transform of the MFM images. For multilayers having an average magnetic domain size of 490 nm, we report a damped precession of the magnetization which decays with a time constant of ∼100 ps and which has a frequency which varies from 8.4 GHz to 17.0 GHz as the external field increases from 192 mT to 398 mT. Fitting the precession dynamics with the Landau-Lifshitz-Gilbert equation we evaluated the damping α, which decreases from 0.18 to 0.05 with increasing magnetic domain sizes (127 nm to 490 nm). These α values are higher than for single layers suggesting an enhanced scattering and spin pumping effects from the Pt adjacent layers. In addition, the precession frequency increases from 2.04 GHz to 11.50 GHz as the anisotropy field of the multilayers increases from 6.5 kOe to 13.0 kOe. Finally, a comparative analysis between micromagnetic simulations and MFM images allowed us to determine the exchange stiffness (Aex) in the [Co60Fe40/Pt]5 multilayers. |
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