a plural - cathode sputtering apparatus capable of producing mixed thin films having a period of stratification as small as 10 å without putting an undue load on the power supplies . two different types of targets are provided on a cathode side , and a substrate onto which sputtering is performed is provided on the anode side . magnetic field generators produce magnetic fields substantially perpendicularly intersecting the electric fields generated between the plate and the targets near and front sides of the targets . the magnetic field generators are each composed of main magnets and electromagnets , which may be combined with the main magnets . electrical currents are produced for exciting the electromagnets which are controlled in such a manner as to change the magnetic intensity of the magnetic fields and to thereby regulate the sputtering discharge .