Effective Measuring Position of Hall Probe and $j_\mathrm{c}$ Characterization of Rectangular HTS Thin Films

Scanning Hall probe (SHP) system is a powerful instrument to investigate the planar distribution of areal critical current density (j
_c
) and defects of high temperature superconducting (HTS) thin film samples. The distance between the effective measuring position and probe bottom (h
₁
) is usually unknown for the commercialized Hall probes. However, h
₁
value has a significant influence on the measurement results, according to the calculation of the magnetic flux density (B
₀
) above the planar center of a rectangular HTS thin film sample. In this paper, a method was proposed to obtain h
₁
by using a series of copper strips and analyzing the relationship of B
₀
against the parameters, such as sample width and current. Then, SHP system was employed to characterize the j
_c
distribution of an HTS thin film fabricated via chemical solution deposition. The relationship of B
₀
and h
₁
could also be utilized to obtain the average j
_c
value (j
_c
^B0
). A series of commercialized coated conductor samples were measured with both SHP and the traditional four-probe method. The feasibility of preliminary evaluation for rectangular HTS thin film samples by using j
_c
^B0
was discussed based on its correlation with the results of four-probe method.