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 nΦ0Hz−1/2, yielding a record low spin noise of 0.29 μBHz−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 Fe3O4 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 Fe3O4.
@article{arxiv.2001.03342,
title = {SQUID-on-tip with single-electron spin sensitivity for high-field and ultra-low temperature nanomagnetic imaging},
author = {Y. Anahory and H. R. Naren and E. O. Lachman and S. Buhbut Sinai and A. Uri and L. Embon and E. Yaakobi and Y. Myasoedov and M. E. Huber and R. Klajn and E. Zeldov},
journal= {arXiv preprint arXiv:2001.03342},
year = {2020}
}