For example, alternating layers of nanostructure Co–Ni–Cu/Cu are the ferromagnetic layer Co–Ni–Cu and the non-magnetic layer Cu. The thickness of these layers is on the order of the electron free path, i.e. several nanometres. Changing the intensity of the externally applied magnetic field from zero to a certain positive value, we may modify magnetic configuration of a multilayer nanostructure to such extent that its electrical resistance will change in a very wide range. In nanostructure Co-Ni-Cu/Cu, the greatest giant magnetoresistance was achieved when Cu layers had thickness of 0.7 nm. Magnetic nanostructures can be used as magnetic field sensors.