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Magnetic chirality at ferromagnet/molecule interfaces

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Salary : yes
Possibility to continue with a Ph.D ? yes
Source of funding : EDPIF

Experimental technics : Scanning Tunneling Microscopy ; Magneto-optical Kerr effect ; Synchrotron (surface x-ray diffraction, x-ray absorption spectroscopy) ; Brillouin scattering
Requirements : solid basis in condensed matter physics and magnetism ; interest for experiments

Up to now, chiral magnetic textures such as skyrmions have been obtained through the symmetry breaking induced by the spin-orbit coupling, generally at the interface between a heavy metal and a ferromagnetic metal. In this internship, we want to explore the possibility to stabilize chiral magnetic structures by using structurally chiral interfaces.

Among the possible routes to obtain chiral interfaces, we will first work on the use of chiral molecules (helicenes) that we will deposit on standard ferromagnetic films (Fe, Co, Ni). It is already known that chiral molecules can induce some electronic spin polarization (the so-called Chiral Induced Spin Selectivity) that can be used to reduce by several order of magnitude the threshold current density required to switch the magnetization by spin-transfer torque [1]. However, little is known on the magnetic structures of such interfaces. We propose to grow in situ (ultra-high vacuum chamber) ultrathin films of ferromagnets with a vanishingly small magnetic anisotropy and to cover them with a single molecular layer of different molecules (coronene, helicene right, helicene left) to observe by magneto-optical Kerr effect how the magnetic cycles are evolving. This will allow to determine how the magnetic anisotropy is modified by the molecule/ferromagnet hybridization [2] and to measure by ex-situ methods if any asymmetric magnetic exchange is induced at such interfaces.

[1] O.B. Dor, Nat. Comm. 2017, 8, 14567
[2] K. Bairagi et al., Phys. Rev. Lett. 2015, 114, 247203 ; K. Bairagi et al., Phys. Rev. B 2018, 98, 85432

Post-scriptum :

Supervisor of the internship/PhD thesis : Vincent Repain, Amandine Bellec
Phone : 01 57 27 62 91
e-mail : vincent.repain@u-paris.fr