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Theme 3 colloquium: 'Van der Waals Halides and the Rise of Magnetism in Flatland' (Lecture)

Tuesday 15 October 2019Add to my calendar
from 16:00
dr. Efrén Navarro-Moratalla (Instituto de Ciencia Molecular (ICMol), Universitat de Valencia, Spain)

Efrén Navarro-MoratallaLayered magnetic materials are at the origin of modern magnetism and among the very first compounds to be explored at cryogenic temperatures by Kammerlingh Onnes almost a century ago [1]. This phenomenon of magnetic ordering in layers (and also in chains) has tantalized condensed matter physicists ever since. The first big milestone in this field would come from Mermin and Wagner, who demonstrated theoretically that long-range ordering in low dimensions is forbidden in an isotropic spin lattice [2]. In order to confirm this celebrated theorem, many experiments have been performed in the aforementioned layered crystals as an approximation of a two-dimensional (2D) spin lattice. However, interlayer coupling in bulk systems is not negligible and an approach for the study of true 2D magnetism has been lacking to the date. With the avenue the 2D materials a genuine approach to low-dimensionality has been unlocked. The realization of long-range magnetic order in a 2D material has also been an enticing concept ever since the discovery of graphene, given the high stakes of the incorporation of magnetism in van der Waals heterostructures for spintronics or topological superconductivity. In this talk I will present our discovery of the first free-standing 2D ferromagnet made out of a single layer of a ferromagnetic insulator: chromium triiodide (CrI3) [3]. Our experiments also showcase the dramatic layer dependence and non-trivial exchange interactions of the magnetic ground states in atomically-thin van der Waals crystals down to the monolayer. In particular, an intriguing metamagnetism emerging in atomically-thin CrI3 flakes contrasts with the bulk ferromagnetism coming from the parent bulk crystals. Finally, I will highlight the potential of this new class of few-layer magnets for optoelectronic, magnetoelectric and spintronic devices exhibiting helical luminescence, the magnetoelectric effect and a prominent magnetoresistance respectively [4-6].


[1] H. Kamerlingh Onnes, Leiden Comm., 1925, 167b, 614 [2] N. D. Mermin & H. Wagner, Phys. Rev. Lett., 1966, 17, 1133 [3] B. Huang et al. Nature 2017, 117, 610 [4] K. L. Seyler et al. Nat. Phys. 2017, 14, 277 [5] B. Huang et al. Nat. Nanotec. 2018, 13, 544 [6] D. R. Klein et al. Science. 2018, 360, 1218.

dr. Johan Mentink