Effect of electrolyte components on the magnetic and magnetoresistive characteristics of Fe-containing plasma electrolytic oxide coatings on titanium

Abstract

The effect replacing Na₃PO₄ with Na₂HPO₄ in aqueous phosphate–borate–tungstate electrolyte that additionally contains Fe₂(C₂O₄)₃ on the magnetic and magnetoresistive characteristics of oxide coating/ titanium composites formed by means of plasma electrolytic oxidation (PEO) is investigated. It is established that PEO coatings with ferromagnetic characteristics form on titanium in an electrolyte containing Na₃PO₄ (pH ~ 11) upon adding iron(III) oxalate, while replacing Na₃PO₄ with Na₂HPO₄ and the respective drop in the pH of the base electrolyte down to 9.8 results in the formation of coatings with different magnetic characteristics. The correlation between changes in the values of the charge carriers’ activation energy and the magnetic susceptibility is demonstrated for the latter. An increase in the electric resistance of coatings in a magnetic field is observed, and the type of the magnetic resistance temperature dependence is established.