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TT: Fachverband Tiefe Temperaturen

TT 6: Superconductivity: Cryodetectors

TT 6.8: Vortrag

Montag, 16. März 2015, 11:30–11:45, H 2053

YBCO nanoSQUIDs applied to the investigation of small spin systems — •Maria Jose Martinez Perez¹, Tobias Schwarz¹, Roman Wölbing¹, Benedikt Müller¹, Christopher F. Reiche², Thomas Mühl², Bernd Büchner², Javier Sese³, Reinhold Kleiner¹, and Dieter Koelle¹ — ¹Physikalisches Institut and Center for Collective Quantum Phenomena in LISA⁺, Universität Tübingen, Germany — ²Leibniz Institute for Solid State and Materials Research IFW Dresden, Germany — ³Instituto de Nanociencia de Aragón and Advanced Microscopy Laboratory, Zaragoza, Spain

We present the realization of ultra-sensitive YBCO nanoSQUIDs based on submicron grain boundary junctions patterned by focused ion beam milling. White flux noise down to ∼ 50nΦ₀/Hz^1/2 has been achieved, yielding spin sensitivities of down to a few µ_B/Hz^1/2 at T=4.2 K. Moreover, we demonstrate that magnetic fields up to the tesla range can be applied, fulfilling a fundamental condition for the study of small spin systems. As a proof-of-principle we present the successful deposition of a Fe-filled carbon nanotube ( ∼ 40 nm in diameter and ∼ 14 µm in length) and an individual Co nanopillar (base diameter of ∼ 50 nm and height ∼ 10 nm) close to the nanoSQUID loop. We show that sub-micrometric control over the particle position lead to large magnetic coupling factors between the nano-loop and the spin system. Together with the possibility of applying large magnetic fields, the latter has allowed us to directly observe the magnetization reversal of these spin systems at different temperatures.