Magnetic and optical properties of MgAl₂O₄-(Ni_0.5Zn_0.5)Fe₂O₄thin films prepared by pulsed laser deposition

Abstract

Thin films composed of MgAl 2 O 4 and (Ni 0.5 Zn 0.5 )Fe 2 O 4 ([MA(100 − x)-NZFx] films) were grown on fused SiO 2 substrates by pulsed laser deposition. X-ray diffraction measurements revealed that the films were polycrystalline, and that their lattice constant varied linearly with composition, indicating the formation of a solid solution. The film with x = 60 was paramagnetic and those with x 70 were ferromagnetic. The films had a transparency above 75% in the visible range, but the transparency decreased with the x value. The optical band gaps were 2.95, 2.55, 2.30 and 1.89 eV for x = 20, 40, 60, 80 and 100, respectively. The Faraday rotation angle increased with x in the visible range, and the film with x = 70 exhibited a value of 2000 degrees cm −1 at 570 nm, which is comparable to the rotation angle of Y 3 Fe 5 O 12 . Owing to their high transparency, which extends into the visible range, the [MA(100 − x)-NZFx] films can be used in novel magneto-optical devices.Keywords: transparent magnetic thin film, solid solution of nickel zinc ferrite and magnesium aluminum spinel, Faraday rotation angle, pulsed laser deposition (PLD)