Fig. 4: Samples and measurement of magnetic cloaking behavior.
From: Magnetic–acoustic biphysical invisible coats for underwater objects
a The measured real and imaginary permeability spectra of the 0.13-mm-thick FM sheet. The inset presents a microscopic optical image of the sample. b Pictures of the fabricated AMS layer and the sample (the assembled biphysical compound coat covering a brass cylinder). The inset in the AMS picture presents a microscopic optical image of one air bubble with a diameter of 130 μm. c Schematic of the measurement setup in a water tank. The probe will scan along the x axis with a minimum distance of 6 mm to the sample. d The measured relative change (top panel: magnitude; bottom panel: phase) of the magnetic field at (0, r3 + 6 mm) caused by the sample and the reference as a function of operation frequency. The solid lines are simulated results, and the symbols are measured results. The reference is a bare brass cylinder without the biphysical coat. e The same measurement but carried out as a function of spatial location along the line (x, r3 + 6 mm) at 25 kHz. The gray region in d, e corresponds to the area |ηH| < 0.5%. The error bars for magnitude are 0.2% and 0.1° for phase. f Schematic of the near-field detection for the sample and reference using a handheld metal scanner (top panel) and the output signals of the scanner via an oscilloscope for reference and sample (bottom panel). The result for the reference is offset upward by 4 V.
