Comparison of FECO films plated from an ammonium-containing sulfate bath and a SBA-containing sulfate bath

Abstract

This study reports on a comparison study of two FeCo electrodeposition electrolytes: an ammonium-containing solution consisting of (NH 4) 2Fe(SO 4) 2 + CoSO 4, and an IBM-Hitachi solution consisting of FeSO 4 + CoSO 4 + acetic acid + SBA (sulfur-bearing-additive). The ammonium solution has very high current efficiency of 85%-95%, while the current efficiency of the IBM-Hitachi solution is only about 60%. However, the films deposited from the ammonium solution have high impurity levels of O and N, which degrade the magnetic properties, including much higher coercivities and magnetic moments limited to 2.2T, in comparison to 2.4T films obtained from the IBM-Hitachi bath. The oxide inclusion was found to be related to higher surface pH during deposition in the ammonium bath, and the N inclusion is believed to be related to some degree of complexation of ammonia with Co 2+ ions.