Ultrafast write-read event in helicity-independent all-optical switching of GdFeCo

Abstract

A femtosecond laser pulse is capable to switch the magnetic state of ferrimagnetic alloy on a picosecond time scale, making devices based on all-optical switching mechanism a strong candidate for ultrafast memories. Although it was experimentally demonstrated that two pulses separated by a few picoseconds were able to drive double switching, the magnetic state evolution was not directly investigated. Here we assume the time required for the average magnetization difference between Fe and Gd per atom to reach −60 % initial state as the period required to read the data after writing. On the basis of semiclassical atomic spin simulations, the effects of the energy density absorbed by the system, the Gd concentration, and the damping parameters on the period required for the write-read event are investigated. Our results show that GdFe alloys with a critical energy density and a compensation point of room temperature can complete the write-read event in the shortest time. By setting the separation of a second laser at 20 ps, we also extend the Gd concentration range for short-delay double switching and reveal the effect of damping on the Gd window for a write-read time in a further study. Our theoretical research could serve as a guidance for optimizing ultrafast electronics for ultrafast write-erase events.