Electroless CoNiFeB soft magnetic thin films with high corrosion resistance

A new soft magnetic CoNiFeB thin film with high saturation magnetic flux density, BS and good corrosion resistance has been prepared by using an electroless deposition method. The electroless CoFeB thin film has high BS but a poor corrosion resistance compared with the electrodeposited NiFe (80-permalloy) film. The addition of Ni to the CoFeB film improves corrosion resistance without affecting its soft magnetic properties. One of the best CoNiFeB films prepared had a composition of Co77Ni13Fe9B1 with excellent magnetic and electrical properties (high BS=1.5–1.7 T, low coercivity, HC=1.2 Oe, low magnetostriction, λS=2.0×10−6, and moderate resistivity, ρ=40 μΩ cm). The new CoNiFeB thin film is suitable for use as a core material for the next generation of merged MR–heads.