CORROSION RESISTANCES OF ELECTRODEPOSITED MAGNETIC THIN FILMS

摘要

Various iron group alloys have been electrodeposited or electroless deposited and evaluated for corrosion resistance, microstructure, electrical resistivity and magnetoresistance. The corrosion resistances depended on deposit composition and microstructure, which were controlled by solution composition and deposition variables. Maximum corrosion resistances were obtained with 50Ni50Fe and 70Co30Ni binary alloys. In general, the corrosion resistances of electrodeposited CoFe films were an order of magnitude lower than CoNi and NiFe films. Substantially increased corrosion resistances were obtained by adding Ni to CoFe alloys. However, addition of B only slightly increased corrosion resistances. For electrodeposited NiFe and CoNi thin film alloys, three different crystal regions were observed: fcc (<50 % Fe), mixed fcc and bcc (60-68 % Fe), and bcc (> 68 % Fe) for NiFe alloys independent of type of anions; fcc ( < 72 % Co), mixed fcc and hcp (72-78 % Co), and hcp ( > 78% Co) for CoNi alloys. The smallest grain size (≈ 50 nm) was obtained in the mixed phase region of both NiFe and CoNi alloys. For CoFe alloys, a mixed phase region was not observed, but only fcc (< 16 % Fe) and bcc phases (> 16 % Fe).