Comparing all-optical switching in synthetic-ferrimagnetic multilayers and alloys

TL;DR

This study compares all-optical switching in synthetic-ferrimagnetic multilayers and alloys, revealing different mechanisms and conditions for switching, supported by experimental data and advanced modeling.

Contribution

It introduces a comprehensive model for laser-induced magnetization dynamics in multilayers and alloys, highlighting distinct switching behaviors without the need for a compensation temperature.

Findings

Co/Gd bilayers can be switched regardless of thickness.

Switching involves a nucleation front at the Co/Gd interface.

Experimental and theoretical results are in agreement.

Abstract

We present an experimental and theoretical investigation of all-optical switching by single femtosecond laser pulses. Our experimental results demonstrate that, unlike rare earth-transition metal ferrimagnetic alloys, Pt/Co/[Ni/Co]$_N$/Gd can be switched in the absence of a magnetization compensation temperature, indicative for strikingly different switching conditions. In order to understand the underlying mechanism, we model the laser-induced magnetization dynamics in Co/Gd bilayers and GdCo alloys on an equal footing, using an extension of the microscopic three-temperature model to multiple magnetic sublattices and including exchange scattering. In agreement with our experimental observations, the model shows that Co/Gd bilayers can be switched for an arbitrary thickness of the Co layer, i.e, even far away from compensating the total Co and Gd magnetic moment. We identify the switching mechanism in Co/Gd bilayers as a front of reversed Co magnetization that nucleates at the Co/Gd interface and propagates through the Co layer driven by exchange scattering.