High-temperature cluster glass state and photomagnetism in Zn- and Ti-substituted NiFe2O4 films

We report on the cluster glass nature and photoinduced magnetization (PIM) of (Ni,Zn,Fe,Ti)3O4 thin films prepared using a pulsed-laser deposition (PLD) technique. The films exhibit cluster glass behaviors with a spin-freezing temperature Tf of approximately 230 K. It was found that the magnetization increases following light irradiation below Tf. The experimental results suggest that the electronic transitions induced by photons are intrinsic to the observed PIM rather than the thermal heating effects resulting from light irradiation. The change in the magnetization from the original dark value at 10 K was approximately 40% for the Ni0.7Zn0.3Fe1.7Ti0.3O4 film, and it was approximately 5% for the Ni0.4Zn0.6Fe2O4 film when the excitation intensity is 1.48mW∕mm2. The analysis of the excitation energy dependence of PIM suggests that an intervalence charge transfer Ti4++Fe2+→Ti3++Fe3+ contributes to the observed enhancement in the PIM of the Ti-substituted films.