  Single Pulse All Optical Helicity Independent Switching (AO-HIS) represents
the ability to reverse the magnetic moment of a nanostructure using a
femtosecond single laser pulse. It is an ultrafast method to manipulate
magnetization without the use of any applied field. Since the first switching
experiments carried on GdFeCo ferrimagnetic systems, single pulse AO-HIS has
been restricted for a while to Gd-based alloys or Gd/FM bilayers where FM is a
ferromagnetic layer. Only recently has AO-HIS been extended to a few other
materials: MnRuGa ferrimagnetic Heusler alloys and Tb/Co multilayers with a
very specific range of thickness and composition. Here, we demonstrate that
single pulse AO-HIS observed in Tb/Co results from a different mechanism than
the one for Gd based samples and that it can be obtained for a large range of
rare earth-transition metal (RE-TM) multilayers, making this phenomenon much
more general. Surprisingly, in this large family of (RE-TM) multilayer systems,
the threshold fluence for switching is observed to be independent of the pulse
duration, up to at least 12 ps. Moreover, at high laser intensities, concentric
ring domain structures are induced, unveiling multiple fluence thresholds.
These striking switching features, which are in contrast to those of AO-HIS in
GdFeCo alloys, concomitant with the demonstration of an in-plane reorientation
of the magnetization, point towards an intrinsic precessional reversal
mechanism. Our results allow expanding the variety of materials with tunable
magnetic properties that can be integrated in complex heterostructures and
provide a pathway to engineer materials for future applications based on
all-optical control of magnetic order.
