Direct preparation of γ-Fe 2O 3 thin film recording media by reactive r.f. sputtering technique

Abstract

A method for the direct preparation of γ-Fe 2O 3 thin films from iron metal was studied. The technique employs an intermittent iron sputter deposition process using a partially masked revolving substrate and a subsequent oxidation process of each deposited layer. Electron diffraction analysis of the films obtained shows superlatice reflections due to iron vacancy ordering, indexed as (110), (210) and (211), together with the reflections of the spinel structure. No reflections from an α-Fe 2O 3 structure can be detected in the films. From their electrical resistivity and lattice parameter values the films are identified as being in an intermediate state between stoichiometric Fe 3O 4 and γ-Fe 2O 3. They exhibit a typical coercive force of 600 Oe, a squareness ratio of 0.75, a saturation magnetization of 3600 G and a coercive squareness ratio of 0.8 for an Fe 0.945Co 0.025Cu 0.03 target. These characteristics confirm that the films are applicable to magnetic recording media.