Figure 4.

Comparison of the gradient of the magnetic field obtained from analytical expressions and finite element method simulation (COMSOL Multiphysics version 3.5) showed good agreement between the two. (A) and (B) show the comparison of $\partial H_y/\partial y$. The unit of the color bar is A²/m. (C) and (D) show the comparison of $\partial H_y/\partial x$. The unit of the color bar is A²/m. (E) and (F) show the comparison of $\partial H_y/\partial z$. The unit of the color bar is A²/m. The plane of the field distribution is at z = 0 (center of the microchannel in the z direction).