Combination of superconducting (SC) and ferromagnetic (FM) sheets into layered SC/FM composites allows to obtain metamaterials with unusual magnetic properties: the effective magnetic permeability along the sheets could be much higher than in the perpendicular direction. One can design the magnetic cloak consisting of a shell from SC/FM composite protecting its inner space against the penetration of a static magnetic field. Difference between such a device and a usual SC or FM shield will be in its un-detectability by magnetic sensors checking the field distribution outside the cloak. Thus it could be considered a magnetic invisibility cloak and one can think about using it e.g. for protecting a sensitive electronic circuitry in an electric machine.

We have prepared a series of SC/FM cloaks using commercial coated conductors as the superconducting elements and various kinds of ferromagnetic sheets as the ferromagnetic elements. Finite element calculation was utilized to optimize the architecture. Experimental testing of the cloaking ability in static magnetic field was performed by scanning the field distribution in vicinity of the cloak. Detectability in low frequency (< 100 Hz) AC magnetic fields was tested in an AC magnetization set-up allowing to see both screening and dissipation signals. Recording of magnetization loops allowed to analyze in detail the dynamics of field interaction with the cloak. Reduction of the detected magnetic signature due to the cloak was confirmed, however it is still not complete. Tests of various arrangements of superconducting and ferromagnetic materials allowed to identify the main problems hindering to achieve a perfect cloaking.