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.
Highlights
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
The free layer is composed of a synthetic ferrimagnetic Co/Gd bilayer (1 and 3 nm respectively) with PMA, which is known to exhibit toggle AOS13
To verify that the origin of the symmetry breaking is truly non-local transfer of angular momentum, we investigate the impact of the magnitude of the generated spin current on the regime where deterministic writing is possible
Summary
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. The second effect, single pulse helicity-independent switching, has far been demonstrated in ferrimagnetic GdFeCo alloys[10,11,12], synthetic ferrimagnetic Co/Gd bilayers[13] and very recently in a ferrimagnetic Heusler alloy[14] This effect relies strongly on transfer of angular momentum between magnetic sublattices, as well as a difference in demagnetization timescales between the involved materials. It should be noted that single pulse helicitydependent switching has been observed in a narrow range of laser fluences for GdFeCo alloys[2,15], owing to magnetizationand helicity-dependent light absorption[16] This same switching process has been demonstrated in synthetic ferrimagnetic Co/Gd bilayers[13], which we will use in this work. The inverse effect where angular momentum is transferred non-locally from a ferromagnetic reference layer to a switching layer has not been addressed so far
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