Detection of Magnetic moments using a NanoSQUID : Limits of resolution and sensitivity in near-field SQUID magnetometry

Vincent Bouchiat (1)

1 NEEL - Quan2m - Interactions modulables dans des états quantiques 2D

We investigate the coupling efficiency of a localized magnetic moment placed at a distance z from a DC-SQUID magnetometer of loop radius a with nanobridges of cross section r^2. Using simple magnetostatic considerations, we show that there exist two detection regimes: the usual far-field regime (z >> a) for which inductive coupling is achieved by the entire loop and a near-field regime (z ≪ a) where nanobridges become the active detecting elements. Simulation shows that the greatest coupling efficiency is obtained in the near-field regime (z ≪ a) when the magnetic moment sits directly on the nanobridge. The maximum coupling limit is given by: 1/2μ0 M . Using nanoscale weak links and typical noise performance of nano-SQUID, we conclude that the limit of single molecular magnet detection can be obtained with r ∼ 1 nm, a value reachable using carbon nanotube Josephson junctions

Domaines: Systèmes mésoscopiques et effet Hall quantique [cond-mat.mes-hall]

Vincent Bouchiat. Detection of Magnetic moments using a NanoSQUID : Limits of resolution and sensitivity in near-field SQUID magnetometry. Superconductor Science and Technology, 2009, 22 (6), pp.064002. ⟨10.1088/0953-2048/22/6/064002⟩. ⟨hal-00994881⟩