I may be wrong, but doesn't each nucleus show magnetic properties in an external magnetic field? Then, together, these magnetic fields influence the chemical shifts of protons.
I think it has to be a "nuclide" which is a nucleus with an odd mass number. Usually it is either Carbon-13 or Proton (H-1) but other things can be used too. If the mass number is odd, it will probably be a nuclide and spin in a magnetic field.