[PCP2] Physics and Chemistry2

[PCP2-06] Scanning SQUID microscopy with vector pick-up coils

Shuichi Kawamata¹, Masahiko Hayashi², Hiroaki Shishido¹, The Dang Vu¹, *Takekazu Ishida¹ (1. Osaka Metropolitan University (Japan), 2. Akita University (Japan))

Keywords:

SQUID,scanning SQUID microscopy,vortex observation,3D observation

We built a scanning SQUID microscope with vector-pick-up coils on the basis of an air-cooled GM refrigerator to make capable of long-term measurements. The SQUID device is the Nb-based one and has three magnetic-flux-detection coils sensing mutually perpendicular magnetic fields. In our earlier work, we repeated the measurements after wiring the sensor three times to obtain the X, Y, and Z componential images of the magnetic field from a single vortex, and we synthesized the 3D mapping of the magnetic field vectors arising from a single vortex [1]. Instead, our novel SQUID microscopy can conduct the vector measurement simultaneously at the same scanning. We used the 3-channel FLL readout circuit (MAGNICON, model XXF-1), and optimized the conditions (drive voltage, drive frequency) of the XYZ piezo-driven stages to improve the positional accuracy. Simultaneous measurements of the X coil, Z coil, and Y coil are performed using the same sensor under the LabVIEW control. We implemented a low-temperature magnetic shield by using a lead superconducting shield in addition to the conventional room-temperature magnetic shield to achieve a very-weak-magnetic-field environment at low temperature. This was necessary to observe the limitted number of vortices in the scanning area. We were successful in observing a single vortex or a few vortices in the scanning area over a wide area, e.g., 201 μm × 201 μm. We demonstrated a long-term continuous measurement (for one day, for a few days, or for one week) without consuming liquid helium. We attempted to conduct an image processing with a 3D data inverse conversion filter [2,3,4] for SQUID microscope data. Our SQUID microscope would be useful to conduct the 3D observation of magnetic flux quanta in the exotic systems.

Acknowledgements: This research was partially supported by Grant-in-Aid for Scientific Research (C) (JP22K04246) from JSPS.

References:

[1] The Dang Vu, Thanh Huy Ho, Shigeyuki Miyajima, Masaki Toji, Yoshitsugu Ninomiya, Hiroaki Shishido, Masaki Maezawa, Mutsuo Hidaka, Masahiko Hayashi, Shuichi Kawamata, and Takekazu Ishida., Supercond. Sci. Technol. 32 (2019) 115006.

[2] M. Hayashi, H. Ebisawa, H. T. Huy, and T. Ishida, Appl. Phys. Lett. 100 (1012) 182601.

[3] Masahiko Hayashi, Takekazu Ishida, Hiroaki Shishido, The Dang Vu, Shuichi Kawamata, J. Phys. Conf. Ser. 2776 (2024) 012001.

[4] Masahiko Hayashi, Yasunari Tanuma, Takekazu Ishida, Hiroaki Shishido, The Dang Vu, Shuichi Kawamata, J. Phys. Conf. Ser. 3054 (2025) 912006.