Transformation of magneto-optical figure of merit for permalloy nanofilms upon oxidation

A series of permalloy nanofilms on glass substrates was fabricated by use of magnetron sputtering. As-deposited and thermally annealed in air oxidized nanofilms were characterized by the AFM and VSM techniques. For a temperature range of 300–475 °C, the magneto-optical figure of merit (FOM) altered in magnitude due to rise in transparency and strong change in the Faraday rotation of the oxidized nanofilms. In the near infrared range, FOM of the 425 °C-oxidized nanofilms was more than one order of magnitude larger than that of the as-deposited ones. The observed magneto-optical properties were addressed to material and structural transformations of the as-deposited nanofilms.