Fig. 2: Design of the magnetic cloak.
From: Magnetic–acoustic biphysical invisible coats for underwater objects
a The relative change ηH of the magnetic field as a function of frequency for the sample with r0 = 0, r1 = 11 mm, r2 = 11.13 mm, and μFM = 82.5 at (0, r3 + 6 mm). The shaded gray area corresponds to the region where |ηH| < 0.5%, which is defined by a lower (fL) and an upper (fU) boundary frequency. b The desired permeability for the FM layer (thickness tFM = r2 – r1) and the bandwidth as a function of the ratio r2/r1 with a fixed upper bound frequency fU = 250 kHz. The solid lines are analytically calculated, and the symbols denote numerically optimized results. c The simulated magnetic field at one phase moment for the sample with the parameters r0 = 10.5 mm, r1 = 11 mm, r2/r1 = 1.012, and μFM = 82.5 at 25 kHz. The arrows represent the direction of local magnetic fields, and the amplitude is denoted by the colors. d The dependences of bound frequencies and bandwidth on the thickness t0 of the inner metal shell.
