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

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 threetemperature 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. arXiv:1908.07292v1 [cond-mat.mes-hall]

Single pulse all-optical toggle switching of magnetization without gadolinium in the ferrimagnet Mn2RuxGa

“…The key difference between MRG and GdFeCo is that while the latter exhibits SP-AOS when measured within about 100 K either above or below its compensation point 11,30 , MRG only switches when the initial temperature is below T comp . Therefore, initially, the angular momentum of the 4c sublattice must be higher than that of 4a to switch successfully.…”

Energy Efficient Control of Ultrafast Spin Current to Induce Single Femtosecond Pulse Switching of a Ferromagnet

“…All optical switching (AOS) of magnetization using ultrashort laser pulses, whether it is helicity dependent [1][2][3][4][5][6] or helicity independent (AO-HIS), [4,[6][7][8][9][10][11][12] exhibits a very interesting out of equilibrium physics as well as promising practical implications. [13] Many attempts to unveil the detailed mechanism of those phenomena have been carried out both theoretically [8,[14][15][16][17][18][19][20][21][22][23][24] and DOI: 10.1002/advs.202001996 experimentally. [1][2][3][4][5][6][7][8][9][10][11][12][25][26][27][28] AO-HIS is observed after a single femtosecond laser pulse and most of the materials showing this effect are gadolinium-based rare earth (RE)/transition metals (TMs) ferrimagnets.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][25][26][27][28] AO-HIS is observed after a single femtosecond laser pulse and most of the materials showing this effect are gadolinium-based rare earth (RE)/transition metals (TMs) ferrimagnets. [24] AO-HIS has been extensively studied in amorphous GdFeCo alloy. [10] It was shown that AO-HIS could only be observed for a limited range of alloy concentration, laser fluence and pulse duration.…”

Exchange-driven all-optical magnetic switching in compensated 3d ferrimagnets

“…It is important during this entire process that both S 4a and S 4c do not simultaneously fall to a level where thermal spin correlations can dominate, leading to loss of magnetic memory and subsequent random behavior. This situation is encountered if the net incident fluence [21,55] is excessive, giving rise to the spatially inhomogeneous pattern shown in Supplemental Fig. S2.…”