Towards high all-optical data writing rates in synthetic ferrimagnets

TL;DR

This study investigates the minimum time delay for all-optical switching in synthetic ferrimagnetic Co/Gd bilayers, demonstrating that it can be as low as 10 ps, with heat diffusion and laser power being critical factors.

Contribution

It provides experimental and modeling insights into ultrafast all-optical switching in layered ferrimagnets, highlighting the importance of heat management and laser parameters.

Findings

Minimum delay for switching as low as 10 ps.

Heat diffusion critically affects switching speed.

Laser power influences the switching process.

Abstract

Although all-optical magnetization switching with fs laser pulses has garnered much technological interest, the ultimate data rates achievable have scarcely been investigated. Recently it has been shown that after a switching event in a GdCo alloy, a second laser pulse arriving 7 ps later can consistently switch the magnetization. However, it is as of yet unknown whether the same holds in layered ferrimagnetic systems, which hold much promise for applications. In this work we investigate the minimum time delay required between two subsequent switching events in synthetic ferrimagnetic Co/Gd bilayers using two fs laser pulses. We experimentally demonstrate that the minimum time delay needed for consistent switching can be as low as 10 ps. Moreover, we demonstrate the importance of engineering heat diffusion away from the magnetic material, as well as control over the laser pulse power. This behavior is reproduced using modelling, where we find that the second switch can occur even when the magnetization is not fully recovered. We further confirm that heat diffusion is a critical factor in reducing the time delay for the second switch, while also confirming a critical dependence on laser power.