Deterministic all-optical magnetization writing facilitated by non-local transfer of spin angular momentum

Abstract

Ever since its discovery around a decade ago, all-optical magnetization switching (AOS) using femtosecond laser pulses has shown potential for future data storage and logic devices. In particular, single pulse helicity independent AOS in certain ferrimagnetic alloys and multilayers is highly efficient and ultrafast. However, in most cases it is a toggle mechanism, which is not desirable for applications. Here we experimentally demonstrate conversion from toggle switching to a deterministic mechanism by biasing AOS in a Co/Gd bilayer with a spin polarized current which is optically generated in an adjacent ferromagnetic reference layer. We show deterministic writing of an 'up' and 'down' state using a sequence of one or two pulses, respectively, and demonstrate the non-local origin by varying the magnitude of the generated spin current. Our demonstration of deterministic magnetization writing could provide an essential step towards the implementation of future optically addressable spintronic memory devices.

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

“…Finally, we note that in a recent work, van Hees et al [28] used the spin current coming from a ferromagnetic layer in order to assist or hinder the AOS of a GdFeCo layer. This is a different but somewhat complementary work, which supports our conclusions.…”

“…[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. [24] AO-HIS has been extensively studied in amorphous GdFeCo alloy.…”

Ultrafast optical manipulation of magnetic order in ferromagnetic materials

“…The required number of pulses can be further reduced to 4 pairs of dual pulses. Another way to promote the efficient AO-HDS of ferromagnetic materials is to take advantage of ferrimagnets and its spin current diffusion [107][108][109]. Specifically, a single 35 fs laser can determinately switch the GeFeCo/Cu/Co/Pt spin-valve structure [108], in which Cu serves as the spacing layer.…”

Polarisation-dependent single-pulse ultrafast optical switching of an elementary ferromagnet

“…The technological potential of this discovery was quickly recognised, leading to proof-of-concept experiments in connection with information storage [2][3][4] . Such laser-driven magnetisation dynamics has also been explored in bulk rare-earth ferromagnets 5 , in ferrimagnets 2,[6][7][8][9][10][11][12][13] , and in ferromagnetic thin films 3,[14][15][16][17][18][19][20] . The underlying physical picture is not yet fully understood, given the diversity of mechanisms that can contribute to or influence the dynamics on distinct or overlapping time scales [21][22][23] .…”