Nanoscale transient gratings of magnetization induced by extreme ultraviolet light*

We describe a methodology for generating and probing periodic nanoscale patterns of magnetization using femtosecond extreme ultraviolet (EUV) pulses from a free electron laser. Two EUV pulses crossed at the sample surface excite a magnetization grating with a period in the tens of nanometers range; the dynamics of this grating are monitored via diffraction of a time-delayed EUV pulse tuned to the M-edge of a transition metal element. The magnetization grating emerges on a subpicosecond time scale as the sample is demagnetized at the maxima of the EUV pump intensity and decay on the time scale of tens of picoseconds. Following the initial report [1], we improved the setup by adding a polarizing mirror analyzer that enables the separation of magnetic and non-magnetic responses of the sample.  We will describe experiments conducted on Co-Ni and Co-Pt multilayers as well as on a CoGd alloy with perpendicular magnetic anisotropy and discuss the dependence of the observed dynamics on the grating period and the pump fluence. We will propose several avenues for studying ultrafast magnetic dynamics on the nanoscale using the transient magnetic gratings approach.

 

[1] D. Ksenzov et al., Nano Lett. 21, 2905 (2021).