Noise and Performance of Magnetic Nanosensor Based on Superconducting Quantum Interference Device

摘要

The nano superconducting quantum interference device (nanoSQUID) is a powerful tool to study the magnetic properties of the nanoparticles at a microscopic level [1-7]. In fact, in the recent years, it has been shown that the magnetic response of nano-objects (nanoparticles, nanobead, small cluster of molecules) can be effectively measured by using a nanoSQUID [8, 9]. Typically, a dc nanoSQUID consists of a square loop having a side length less than 1 μm interrupted by two nanometric niobium constrictions (Dayem bridges) [2-4]. A small capture area improves the magnetic coupling between the SQUID and the nano-object under investigation allowing to obtain a sensitivity as high as few tens of Bohr magnetons per unit bandwidth [2-4]. In this paper, the design, the fabrication, and the characterization of hysteretic nanoSQUIDs based on Dayem nanobridges are reported. The effectiveness of such devices to measure magnetization and relaxation of iron oxide nanoparticles having a mean size ～8 nm demonstrated that our nano-devices are useful tools for nanomagnetism investigation.