Cathode assembly having rotating magnetic-field shunt and method of making magnetic recording media

A cathode assembly for use in a magnetron sputtering apparatus, comprising:

• a sputtering target having a planar sputtering surface;
• north and south magnetic poles disposed with respect to the target to produce a magnetic field over the target surface for magnetron sputtering;
• a magnetic-field shunt disposed between the target and said magnetic poles;
• and
• means for moving the shunt relative to the poles between first and second positions at which the shunt functions as an extension of the north and south poles;
• whereby repeated movement of the shunt between such first and second positions shifts the magnetic-field between first and second target regions, respectively, to produce preferential target erosion in said first and second target regions.

A method of forming on a substrate by sputter deposition a thin-film layer in a magnetic recording medium, comprising

• placing a substrate in a sputtering chamber including a cathode assembly composed of (i) a sputtering target having a planar sputtering surface, (ii) north and south magnetic poles disposed with respect to the target to produce a magnetic field over the target surface for magnetron sputtering, (iii) a magnetic-field shunt disposed between the target and said magnetic poles, and (iv) means for moving the shunt relative to the poles between first and second positions at which the magnetic field on the target surface causes preferential target erosion at first and second target regions, respectively, whereby repeated movement of the shunt between such first and second positions during target sputtering is effective to produce preferential erosion over said first and second regions, respectively;
• igniting a sputtering plasma by energizing said target;
• moving said shunt repeatedly between said first and second positions;
• and
• sputtering said layer onto said substrate.