SQUID-on-tip with single-electron spin sensitivity for high-field and ultra-low temperature nanomagnetic imaging

Abstract

Scanning nanoscale superconducting quantum interference devices (nanoSQUIDs) are of growing interest for highly sensitive quantitative imaging of magnetic, spintronic, and transport properties of low-dimensional systems. Utilizing specifically designed grooved quartz capillaries pulled into a sharp pipette, we have fabricated the smallest SQUID-on-tip (SOT) devices with effective diameters down to 39 nm. Integration of a resistive shunt in close proximity to the pipette apex combined with self-aligned deposition of In and Sn, have resulted in SOT with a flux noise of 42 n${\Phi }_0$Hz${}^{-1/2}$, yielding a record low spin noise of 0.29 ${\mu }_B$Hz${}^{-1/2}$. In addition, the new SOTs function at sub-Kelvin temperatures and in high magnetic fields of over 2.5 T. Integrating the SOTs into a scanning probe microscope allowed us to image the stray field of a single Fe${}_3$O${}_4$ nanocube at 300 mK. Our results show that the easy magnetization axis direction undergoes a transition from the (111) direction at room temperature to an in-plane orientation, which could be attributed to the Verwey phase transition in Fe${}_3$O${}_4$.

20 pages, 8 figures

References in corpus (9)

• Probing magnetism in 2D materials at the nanoscale with single spin microscopy
• Nanoscale magnetic imaging of a single electron spin under ambient conditions
• Imaging of super-fast dynamics and flow instabilities of superconducting vortices
• Imaging resonant dissipation from individual atomic defects in graphene
• A three-junction SQUID-on-tip with tunable in-plane and out-of-plane magnetic field sensitivity
• Analysing Magnetism Using Scanning SQUID Microscopy
• NanoSQUID magnetometry of individual cobalt nanoparticles grown by focused electron beam induced deposition
• Observation of superparamagnetism in coexistence with quantum anomalous Hall C=$\pm$1 and C=0 Chern states
• Verwey transition in single magnetite nanoparticles

Cited by in corpus (8)

• Direct Observation of a Superconducting Vortex Diode
• Magnetic imaging and domain nucleation in CrSBr down to the 2D limit
• Interior and edge magnetization in thin exfoliated CrGeTe3 films
• 2D ferromagnetism at finite temperatures under quantum scrutiny
• Nano-Patterned Magnetic Edges in CrGeTe3 for Quasi 1-D Spintronic Devices
• Scanning SQUID-on-tip microscope in a top-loading cryogen-free dilution refrigerator
• Geometric Scaling of the Current-Phase Relation of Niobium Nano-Bridge Junctions
• Fabrication of Nb and MoGe SQUID-on-tip probes by magnetron sputtering