Role of Element-Specific Damping on the Ultrafast, Helicity-Independent All-Optical Switching Dynamics in Amorphous (Gd,Tb)Co Thin Films

Abstract

Ultrafast control of the magnetization in ps timescales by fs laser pulses offers an attractive avenue for applications such as fast magnetic devices for logic and memory. However, ultrafast helicity-independent all-optical switching (HI-AOS) of the magnetization has thus far only been observed in Gd-based, ferrimagnetic amorphous (\textit{a}-) rare earth-transition metal (\textit{a}-RE-TM) systems, and a comprehensive understanding of the reversal mechanism remains elusive. Here, we report HI-AOS in ferrimagnetic \textit{a}-Gd${}_{22-x}$Tb${}_x$Co${}_{78}$ thin films, from x = 0 to x = 18, and elucidate the role of Gd in HI-AOS in \textit{a}-RE-TM alloys and multilayers. Increasing Tb content results in increasing perpendicular magnetic anisotropy and coercivity, without modifying magnetization density, and slower remagnetization rates and higher critical fluences for switching but still shows picosecond HI-AOS. Simulations of the atomistic spin dynamics based on the two-temperature model reproduce these results qualitatively and predict that the lower damping on the RE sublattice arising from the small spin-orbit coupling of Gd (with $L=0$) is instrumental for the faster dynamics and lower critical fluences of the Gd-rich alloys. Annealing \textit{a}-Gd${}_{10}$Tb${}_{12}$Co${}_{78}$ leads to slower dynamics which we argue is due to an increase in damping. These simulations strongly indicate that acounting for element-specific damping is crucial in understanding HI-AOS phenomena. The results suggest that engineering the element specific damping of materials can open up new classes of materials that exhibit low-energy, ultrafast HI-AOS.

References in corpus (3)

• Dynamic approach for micromagnetics close to the Curie temperature
• Scaling of intrinsic Gilbert damping with spin-orbital coupling strength
• Origin of intrinsic Gilbert damping

Cited by in corpus (10)

• Unifying femtosecond and picosecond single-pulse magnetic switching in GdFeCo
• Universal criteria for single femtosecond pulse ultrafast magnetization switching in ferrimagnets
• Helicity-independent all-optical switching of magnetization in ferrimagnetic alloys
• Plasmon-enhanced optical control of magnetism at the nanoscale via the inverse Faraday effect
• Single-pulse all-optical switching in amorphous Dy${}_x$Co${}_{1-x}$ and Tb${}_x$Co${}_{1-x}$
• Wide-field magneto-optical microscope to access quantitative magnetization dynamics with femtosecond temporal and sub-micrometer spatial resolution
• Realistic micromagnetic description of all-optical ultrafast switching processes in ferrimagnetic alloys
• Analysis of ultrafast magnetization switching dynamics in exchange-coupled ferromagnet-ferrimagnet heterostructures
• Ultrafast single-pulse all-optical switching in synthetic ferrimagnetic Tb/Co/Gd multilayers
• Towards high all-optical data writing rates in synthetic ferrimagnets