Absence of field anisotropy in the intrinsic ferromagnetic signals of highly oriented pyrolytic graphite |
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Authors: | A. Ballestar,A. SetzerP. Esquinazi,N. Garcí a |
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Affiliation: | a Laboratorio de Física y Sistemas Pequeños y Nanotecnología, CSIC, Serano 144, E-28006 Madrid, Spain b Division of Superconductivity and Magnetism, Linnéstraße 5, Universität Leipzig, D-04103 Leipzig, Germany |
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Abstract: | We have measured the magnetization of bulk samples of highly oriented pyrolytic graphite (HOPG) at magnetic fields applied parallel and perpendicular to the graphene layers. Within experimental error the intrinsic ferromagnetic signals of the samples show similar magnetic moments at saturation for the two magnetic field directions, in contrast to recently published data (J. ?ervenka et al., Nat. Phys. 5 (2009) 840). To check that the SQUID device provides correctly the small ferromagnetic signals obtained after subtracting the 100 times larger diamagnetic background, we have prepared a sample with a superconducting Pb-film deposited on one of the HOPG surfaces. We show that the field dependence of the measured magnetic moment and after the background subtraction is highly reliable even in the sub-μ emu range providing the real magnetic properties of the embedded small ferromagnetic and superconducting signals. |
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Keywords: | Magnetic carbon Magnetic anisotropy |
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