We have prepared a zinc ferrite ͑ZnF 2 O 4 ͒ thin film 85 nm thick deposited on a silica glass substrate by using a radio frequency sputtering method. Faraday effect measurements have been carried out not only for as-deposited but also for annealed thin films. The thin film annealed at 300°C as well as the as-deposited thin film exhibit a large Faraday rotation angle at a wavelength of around 390 nm. In particular, the thin film annealed at 300°C manifests the largest Faraday effect among the

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... esent thin films; the rotation angle of 1.65°/ m is attained at a wavelength of 386 nm. The thin films 1.08 m thick exhibit a large magnetization at room temperature, and the dependence of the magnetization on the external magnetic field is suggestive of a ferrimagnetic behavior.