Structural and magnetic characterization of electron- and ion-induced defects on HOPG

N. BAJALES; P. FELAJ; S. MONTORO; M. ARANA; G. CASTELLANO; J. FERRÓN; P. G. BERCOFF

Buenos Aires

Workshop; X Latin American Workshop on Magnetism and Magnetic Materials (X-LAW3M); 2013

Pristine carbon materials are strongly diamagnetic. However, since the early 2000s, the existence of ferro-(antiferro-) magnetic ordering in these materials has become a widely-discussed problem. The topic is still controversial, and experimental observations of magnetism have often been attributed to parasitic signals from transition metal impurities [1]. Gradually, magnetism of carbon allotropes is getting more attention, and though the nature of magnetic ordering in all-carbon materials, such as highly oriented pyrolitic graphite (HOPG) is still not completely clear [2], one thing seems evident: for the appearance of the unconventional magnetism of carbon, irregularities in the carbon lattice are crucial. In particular, ferromagnetism depending on the irradiation dose has been reported for graphite irradiated with helium and protons [3]. In this work we report structural and magnetic characterization of HOPG with defects induced by electron and ion bombardment for di_erent irradiation doses. In order to characterize small surface changes, we use secondary electron emission (SEE) induced by electron and ion bombardment and Raman spectroscopy. The structural and morphological characterization is carried out with X-ray di_raction, atomic force microscopy and high-resolution scanning electron microscopy. The magnetic properties are measured with a SQUID and magnetic force microscopy. [1] R. R. Nair, M. Sepioni, I.-L. Tsai, O. Lehtinen, J. Keinonen, A. V. Krasheninnikov, T. Thomson, A. K. Geim, and I. V. Grigorieva. Nat. Phys. (2012) doi: 10.1038/NPHYS2183. [2] P. Esquinazi, A. Setzer, R. Hohne, C. Semmelhack, Y. Kopelevich, D. Spemann, T. Butz, B. Kohlstrunk, and M. Losche. Phys. Rev. B 66 (2002), p. 024429. [3] P. Esquinazi, D. Spemann, R. Hohne, A. Setzer, K. H. Han, and T. Butz. Phys. Rev. Lett. 91 (2003), p. 227201.