Fumiyoshi Kirino, Shigekazu Ohotomo and Nagatsugu Koiso
Central Research Laboratory Hitachi, Ltd., Kokubunji 185
Electrochemical characteristics of single crystalline Mn-Zn ferrites with different MnO/ZnO ratios were studied when annealed in a vaccum and N2 atmospheres. The thermal treatment condition, which was similar to that used in the magnetic head fabrication process, consists three steps. The ferrite sample was first annealed at 1073 K for 1800 s in a vacuum, then at 873 K for 1800 s in N2 flow, and finally at 673 K for 1.08{×}104 s in N2 flow. The electrochemical characteristics of ferrite depended on the composition of ferrite (MnO/ZnO ratio). When the (MnO/ZnO ratio was 1.48, it showed the highest corrosion resistance. The electrochemical characteristics of the ferrite did not change, after passing the thorough annealing. When the cathode process of the Mn-Zn ferrite (MnO/ZnO ratio is 1.48) was compared with the anode process of the 9.8 at% Al-doped Fe-Ta-C film, it was found that any galvanic couple is not formed. These results show that electrochemical corrosion does not occur at the interface between the Mn-Zn ferrite and the Al-doped Fe-Ta-C film. The magnetic heads employing the single crystalline Mn-Zn ferrite and the Al-doped Fe-Ta-C film have a high resistance against corrosion.
(Received March 12, 1997)
corrosion resistance, electrochemical characteristics, manganese-zinc ferrite, thermal treatment, corrosion potential
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