How To Build An Antimagnet - Technology Review: The basic ingredients are two materials; one with a permeability that is smaller than 1 in one direction and one with a permeability greater than one in a perpendicular direction.
Materials with these permeabilities are easy to find. Superconductors have a permeability of 0 and ordinary ferromagnets have a permeability greater than 1.
The difficulty is creating a material with both these properties at the same time. Sanchez and co solve the problem with a design consisting of ferromagnetic shells coated with a superconducting layer.
The result is a device that can completely shield the outside world from a magnet inside it.