(a) Measured force map of a sharply focused APB using PiFM, which exhibits a certain tip-induced anisotropy. (b) Corrected intensity distribution from the fitted model, removing tip anisotropy and noise [8]. (c) Retrieved electric and magnetic field of the sharply focused APB normalized to its maximum value. The highlighted magnetic dominant region is defined as when the normalized local field admittance F_Y = η|H_z/E_ρ| > 10, where η is the free space impedance [8,14,16].