Authors: B. Müller, J. Lin, J. Linek, M. Karrer, F. Limberger, L. Koch, E. Goldobin, R. Kleiner, D. Koelle, V. Morosh, T. Weimann, O. F. Kieler, J. Sesé, M. J. Martínez-Pérez
IEEE International Superconductive Electronics Conference (ISEC), Riverside, CA, USA, 2019, pp. 1-3
Abstract: We report on the fabrication, performance and application of sensitive YBa 2 Cu 3 O 7 (YBCO) and Nb nanoSQUIDs to magnetization reversal measurements of individual magnetic nanoparticles. The YBCO SQUIDs are based on grain boundary Josephson junctions and are patterned in a single layer of epitaxially grown YBCO films by Ga focused ion beam milling. The Nb SQUIDs contain sandwich-type Josephson junctions with normal conducting HfTi barriers; they are fabricated with a multilayer technology that includes patterning by e-beam lithography and a combination of milling techniques and chemical-mechanical polishing. Due to the small inductance of the SQUID loops, ultralow white flux noise at 4.2 K can be achieved, which yields spin sensitivities of down to a few Bohr magnetons per unit bandwidth for a magnetic nanoparticle placed at 10 nm distance to the SQUID loop.