Institut Jean Lamour, University of Lorraine, Nancy, France

Abstract

Since the first observation of magnetization switching in ferrimagnetic GdFeCo alloy films using femtosecond laser pulses in 2007 [1], understanding the mechanism behind all-optical switching (AOS) is becoming a topic of huge interest in the magnetism community.

Moreover ultrafast magnetization switching in magnetic material thin film without any applied external magnetic field is drawing a lot of attention for the development of future ultrafast and energy efficient magnetic data storage and memories. Two type of all optical

switching have then ben distinguished: Helicity Independent – All Optical Switching (HI-AOS) and Helicity Dependent – All Optical Switching (HD-AOS). HI-AOS has only been demonstrated for GdFeCo based material and is observed after a single laser pulse [2].

After one pulse the magnetization is reversed in the opposite direction independently of the light helicity. On the other hand, HD-AOS has been observed for a large variety of magnetic material such as ferrimagnetic alloy,ferrimagnetic multilayer, ferromagnet, and granular

media [3-5]. However several studies shows that HD-AOS is only observed after multiple pulses [6]. During the presentation I will present experimental results showing that the number of pulses can be reduced significantly in order to switch ferromagnetic [Co/Pt] multilayers using only several light pulses. Those results can be explained by considering the transfer of heat and angular from light to the sample’s electron bath [7]. In all the previously reported experiments light is used to manipulate magnetization. However, recently we have engineered multilayer structures in order to create hot electrons femto second pulses. We have demonstrated that the magnetization ofGdFeCo can be switched using a femto-second hot electron pulse with no direct light interaction [8] which confirm the work from Wilson et al [9]. Indeed they reported the switching of GdFeCo/Au bilayer via hot electrons generated by single pulse femtosecond laser. Moreover we have studied the magnetization reversal in a GdFeCo / Cu / [Co/Pt] spin valve structure. We observed single shot switching of both the ferrimagnetic GdFeCo and the ferromagnetic [Co/Pt] layer. The magnetisation switching is found to be mediated by spin polarized hot electron transport [10].

Refrences:

[1] Phys. Rev. Lett. 99, 047601 (2007).

[2] Nat. Commun. 3, 666 (2012).

[3] Appl. Phys. Lett. 101, 162408 (2012)

[4] Nat. Mater. 13, 286 (2014).

[5] Science 1253493 (2014).

[6 ] Phys. Rev. B 94, 064412 (2016)

[7] G. Kichin et al in Preparation

[8] Adv Mater 29, 1703474 (2017)

[9] Phys. Rev. B 95, 180409(R) (2017)

[10] Adv. Mater 30, 1804004 (2018)

Brief Biography

Stéphane Mangin received M.S and Ph.D in physics at the University Joseph Fourrier, France in 1994 and 1997 respectively. He then undertook postdoctor at the Catholic University of Leuven, Belgium in 1997-1998 and became a full professor

at the University of Lorraine,France in 2008 .Prof. S. Mangin is now the head of the Nanomagnetism & spintronic team at the Institut Jean Lamour in Nancy. His current research interest focus on the physical properties of magnetic nanostructures,

study of magnetic configurations in coupled bilayer system, and spin transfer torque in nano pillars and wires. Especially, Stéphane Mangin and his team are working on the manipulation of magnetization in nanomaterials by femtosecond laser excitation,

with a view to in-depth understanding of fundamental mechanisms and for the development of new generations of memories and magnetic sensors. He has published over 100 articles in general science journals with high impact factors, such as

Nature Materials, Advanced Materials, and Physical Review Letters etc.

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