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 (<inline-formula><tex-math notation="LaTeX">$j_\mathrm{c}$</tex-math></inline-formula>) and defects of high temperature superconducting (HTS) thin film samples. The distance between the effective measuring position and probe bottom (<inline-formula><tex-math notation="LaTeX">$h_1$</tex-math></inline-formula>) is usually unknown for the commercialized Hall probes. However, <inline-formula><tex-math notation="LaTeX">$h_1$</tex-math></inline-formula> value has a significant influence on the measurement results, according to the calculation of the magnetic flux density (<inline-formula><tex-math notation="LaTeX">$B_0$</tex-math></inline-formula>) above the planar center of a rectangular HTS thin film sample. In this paper, a method was proposed to obtain <inline-formula><tex-math notation="LaTeX">$h_1$</tex-math></inline-formula> by using a series of copper strips and analyzing the relationship of <inline-formula><tex-math notation="LaTeX">$B_0$</tex-math></inline-formula> against the parameters, such as sample width and current. Then, SHP system was employed to characterize the <inline-formula><tex-math notation="LaTeX">$j_\mathrm{c}$</tex-math></inline-formula> distribution of an HTS thin film fabricated via chemical solution deposition. The relationship of <inline-formula><tex-math notation="LaTeX">$B_0$</tex-math></inline-formula> and <inline-formula><tex-math notation="LaTeX">$h_1$</tex-math></inline-formula> could also be utilized to obtain the average <inline-formula><tex-math notation="LaTeX">$j_\mathrm{c}$</tex-math></inline-formula> value (<inline-formula><tex-math notation="LaTeX">$j_\mathrm{c}^\mathrm{B0}$</tex-math></inline-formula>). 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 <inline-formula><tex-math notation="LaTeX">$j_\mathrm{c}^\mathrm{B0}$</tex-math></inline-formula> was discussed based on its correlation with the results of four-probe method.