Spin-half paramagnetism in graphene induced by point defects

By R. Nair, M. Sepioni, I-Ling Tsai, O. Lehtinen, J. Keinonen, A. Krasheninnikov, T. Thomson, A.K. Geim, I. V. Grigorieva. Nature Physics, 2011

755 citations recorded by the source corpus.

The presence, or otherwise, of magnetism in graphene has been the subject of much debate. A systematic study of point defects—a widely suggested source of ferromagnetism in graphene—suggests that although they can exhibit net spin, they remain paramagnetic, even at liquid helium temperature. The possibility to induce a magnetic response in graphene by the introduction of defects has been generating much interest, as this would expand the already impressive list of its special properties and allow novel devices where charge and spin manipulation could be combined. So far there have been many theoretical studies (for reviews, see refs 1, 2, 3) predicting that point defects in graphene should carry magnetic moments μ∼μB and these can in principle couple (anti)ferromagnetically1,2,3,4,5,6,7,8,9,10,11,12. However, experimental evidence for such magnetism remains both scarce and controversial13,14,15,16. Here we show that point defects in graphene—(1) fluorine adatoms in concentrations x gradually increasing to stoichiometric fluorographene CFx=1.0 (ref. 17) and (2) irradiation defects (vacancies)—carry magnetic moments with spin 1/2. Both types of defect lead to notable paramagnetism but no magnetic ordering could be detected down to liquid helium temperatures. The induced paramagnetism dominates graphene’s low-temperature magnetic properties, despite the fact that the maximum response we could achieve was limited to one moment per approximately 1,000 carbon atoms. This limitation is explained by clustering of adatoms and, for the case of vacancies, by the loss of graphene’s structural stability. Our work clarifies the controversial issue of graphene’s magnetism and sets limits for other graphitic compounds.

Subfields: Biomedical Engineering, Electrical and Electronic Engineering, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/2357c6e379fd3c2dce9986a9e6fada15d935c0af

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Citations in the corpus

Two-dimensional magnetic crystals and emergent heterostructure devices (2019, background): “One report (23) disagreed with the feasibility of these approaches to realizing long-range ferromagnetic order, because the authors only observed the paramagnetic response in graphene with fluorine adatoms or vacancies at liquid helium temperatures, and observed a maximum response of about 1 magneti”
A simple method for graphene production based on exfoliation of graphite in water using 1-pyrenesulfonic acid sodium salt (2013, methodology): “This type of suspensions has been already well characterized in previous works [18,19], so we simply use them as reference in order to compare the quality of the dispersions obtained with Py–1SO3.”
2D materials for spintronic devices (2020, background): “46 Å) matches almost perfectly that of (111) Co or Ni (the lattice mismatch between them is only less than 1.”
Discovery of intrinsic ferromagnetism in two-dimensional van der Waals crystals (2017, background): “) have been derived primarily from the electron charge degree of freedom, whereas 2D spintronics(1-3,15) based on vdW crystals is still in its infancy, severely hindered by the lack of long-range ferromagnetic order that is crucial for macroscopic magnetic effects.(4,7) The emergence of ferromagneti”
Colloquium : Spintronics in graphene and other two-dimensional materials (2019, background): “Nevertheless, experiments have so far demonstrated a paramagnetic response (McCreary et al., 2012; Nair et al., 2012).”
Spintronics and pseudospintronics in graphene and topological insulators. (2012, background): “Unfortunately, the coupling between these defects and graphene's π orbitals seems so far to be weak [88][89].”
Colloquium: Graphene spectroscopy (2014, background): “Graphene crystals of nm-size can be synthesized by reduction of graphene oxide5 or by ultrasonic cleavage of graphite in an organic solvent (Hernandez et al., 2008; Nair et al., 2012).”