Abstrakt
Magnetization state control by a single ultrashort laser pulse has recently been the focus of scientific interest since it offers extremely short switching times, does not require an external magnetic field, and can be operated at room temperature. Additionally, selective and reversible photo-magnetic switching in Co-doped yttrium iron garnet films (YIG:Co) can be obtained. This recording was characterized by a switching time of about 20 ps. Moreover, because of its resonant character the write-read events are accompanied by an unprecedentedly low heat load [1]. Microscopically, in this mechanism incident linearly polarized pump pulse excites strongly anisotropic garnet ions, generating a photo-induced contribution to the effective field of magnetic anisotropy [2]. This strong and short-living addition, driven by an external light pulse can trigger the precession or even switch the magnetization. However, while the dynamic is described by the LLG equation, other contributions to the effective field of anisotropy, both external and internal, clearly affect the trajectory of the magnetization movement.
The heat load threshold of photo-magnetic switching has been found for different thicknesses of garnet films by means of magnetic domain imaging. For our experiments, we used Co-doped yttrium iron garnet thin films (YIG:Co). Comparative results were obtained from a batch of 2-8 µm-thick YIG:Co single-crystal films fabricated from liquid phase epitaxy on (001)-oriented Gd3Ga5O12 substrate without miscut angle, which were later chemically etched to the set thickness. In these garnets, cubic magnetic anisotropy dominanates uniaxial grown-induced anisotropy contrubution. Here we investigate the effects of the garnet on magnetic anisotropy and photo-magnetic dynamics. Moreover, we examine the possibility to use an electric field to modify the anisotropy in garnet films. With the sample patterned with gold-plated electrical contacts, we apply the electric field affecting the laser-induced magnetization dynamics. Combining ultrafast laser pulse and pulse of electrical field illustrates the high potential of the magnetic dielectrics for cold ultrafast magnetic recording.