Regensburg 2019 – wissenschaftliches Programm
TT 57.9: Vortrag
Donnerstag, 4. April 2019, 17:15–17:30, H7
Unconventional Magnetic Properties of Nitrogen-doped Diamond: Coexistence of superconductivity and superparamagnetism — •Jose Luis Barzola Quiquia1, Markus Stiller1, Pablo Esquinazi1, Axel Molle1, Ralf Wunderlich1, Sebastian Pessagna1, Jan Meijer1, Wilhelm Kossack2, and Sergei Buga3 — 1Felix-Bloch Institute for Solid State Physics, University of Leipzig, 04103 Leipzig, Germany — 2Peter-Debye Institute for Soft Matter Physics, University of Leipzig, 04103 Leipzig, Germany — 3Technological Institute for Superhard and Novel Carbon Materials, 7a Centralnaya street, Troitsk, Moscow, 108840 Russia
We report on the magnetization of nitrogen-doped single crystalline diamond bulk samples. We found unconventional field and temperature hysteresis loops in the magnetization at T < 25 K. The results indicate the superposition of superparamagnetism and superconductivity in eight measured samples with different nitrogen concentration ( < 200 ppm). At temperatures above 25 K, the samples show diamagnetic behavior similar to undoped diamond. The coexistence of superparamagnetism and superconductivity is attributed to the nitrogen doping and the existence of defective regions. To support our results and interpretation we investigated the magnetic properties of ferromagnetic/high-temperature superconducting oxide bilayers. The results obtained from those bilayers show remarkable similarities to the ones in nitrogen-doped diamond. Using a simple model based on the superposition of a superparamagnetic, a superconducting and a diamagnetic contribution, we can describe very well all results.