Regensburg 2016 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 51: Transport: Spintronics and Magnetotransport
(Joint session of DS, HL, MA and TT, organized by TT)
DS 51.7: Vortrag
Donnerstag, 10. März 2016, 18:15–18:30, H23
Colossal Magnetoresistance observed in Natural Graphite — •Jose Barzola-Quiquia1, Mahsa Zoraghi1, Markus Stiller1, Christian Precker1, Ana Champi2, and Pablo Esquinazi1 — 1Institute for Experimental Physics II, University of Leipzig, 04103 Leipzig, Germany — 2Centro de Ciencias Naturais e Humanas Universidade Federal do ABC, Sao Paulo- Brasil
In this work, the electrical transport properties of a bulk natural graphite flake extracted from a mine in Brazil were investigated. The sample showed metallic behavior and the changes in the magnetoresistance (MR) at 5 K and 7 T shows 1123600% change when the field was applied parallel to the c-axis. This value was not yet reported in any graphite sample in the literature. Applying constant magnetic field, resistance measurements as a function of the temperature show also a magnetic field induces metal-insulator transition (MIT), with a small critical field B0≈ 10 mT compared to literature. We observed also that at fields B > 0.2 T a metallic reentrance was observed that remains up to ≈ 50 K. STEM measurements reveal the presence of interfaces in the investigated material. Therefore, the observed transport properties are not an intrinsic behavior of the graphite sample but due to the presence of these interfaces. Interfaces in the sample are formed at the interfaces between two crystalline regions inside the sample where a two dimensional electron gas (2DEG) system appears. Raman measurements reveal that our samples are free from any other defects.