Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 3: Magnetic Materials I
MA 3.7: Vortrag
Montag, 26. März 2007, 11:45–12:00, H22
Magnetic order in highly oriented graphite irradiated with protons at low temperatures — •Jose Barzola-Quiquia1, Martin Rothermel2, Annette Setzer1, Pablo Esquinazi1, and Tilman Butz2 — 1Division of Superconductivity and Magnetism, Institute for Experimental Physics II, University of Leipzig, Linnéstr. 5, 04103 Leipzig, Germany — 2Division of Nuclear Solid State Physics, Institute for Experimental Physics II, University of Leipzig, Linnéstrasse 5, 04103 Leipzig, Germany
In this contribution we compare the magnetic properties of graphite samples proton irradiated at room and low (T=110K) temperatures. An array of 160x160 spots of micrometer size were proton irradiated with fluence of ∼1nC/µm2 in highly oriented graphite samples, two of them at low and one at room temperature. Special sample holders, which enable irradiation and SQUID measurements without any sample handling, allow us to study with high accuracy the changes produced by the irradiation on the magnetic properties. SQUID measurements reveal clear differences between the low and room temperatures irradiations. The samples irradiated at low temperature show larger ferromagnetic contribution. From the temperature dependence of the ferromagnetic contribution we obtain a Curie temperature of the order of 400K for the micrometer size irradiated spots. The total amount of magnetic impurities, measured in situ and during irradiation, is below 0.3 ppm and cannot explain the observed magnetic order. Our results confirmed previous results published earlier in Phys..Rev.Lett. 91, 227201 (2003).