For a magnetic shield a solution for a designable time-constant shall be implemented. This is achieved by a compound material for a magnetic shield of a magnetic resonance (MR) imaging system the compound material comprising fragmented superconducting material (2), wherein the fragmented superconducting material (2) comprises fibers or wires (4), wherein the fibers or wires (4) of the fragmented superconducting material (2) are dispersed in a normal conducting metal or alloy (3). The present invention also refers to a magnetic shield for a magnetic resonance (MR) imaging system, wherein at least one surface of the magnetic shield (1) is covered with such a compound material. The present invention also refers to a magnetic resonance (MR) imaging system comprising such a magnetic shield and to a method for producing a compound material for a magnetic shield of a magnetic resonance (MR) imaging system.