Drastic change of giant magnetoresistance of Co/Cu multilayer by decreasing residual impurities in sputtering atmosphere

In order to clarify the influence of residual impurities in the sputtering atmosphere on the microstructure and the giant magnetoresistance (GMR), Co/ Cu multilayers were fabricated by changing the chamber pressures, P-b, just before introducing processing gas. P-b was controlled by changing the pump ing time after venting the chamber with air. A drastic change of magneto re sistance (MR) ratio from 48% to 14% was observed, when P-b was changed slig htly from 7 x 10(-8) to 3 x 10(-8) Torr. In that P-b region, the root mean square (rms) roughness increased discontinuously from 3.7 to 4.6 Angstrom a s P-b was lowered. The abrupt drop of the MR ratio was accounted for by the decrease of the antiferromagnetic coupling accompanied by the increase of interfacial roughness. (C) 1999 American Institute of Physics. [S0021-8979( 99)73608-X].