Morphological, structural and magnetic evolution of sputtered Fe70Ga30 thin films upon annealing in oxygen atmosphere

Abstract

We report on the evolution of uncapped Fe 70 Ga 30 layers deposited by sputtering and post-growth annealed in oxygen atmosphere in a temperature range from 500 °C to 800 °C. We have investigated the morphology, structure and magnetic properties of films with a thickness of 200 nm deposited on Mo buffer layers on glass substrates. X-ray diffractometry shows a decrease of the lattice parameter up to 600 °C whereas a further increase of the temperature up to 800 °C promotes the transformation to Fe 2 O 3. We have observed by x-ray absorption fine structure the partial oxidation of Ga and the formation of Ga aggregates at 600 °C. These aggregates form Ga-rich bubbles that can be observed on the sample surface from which Ga evaporates leaving a Ga-poor layer that is later oxidized into Fe 2 O 3. The thermal treatment on oxygen atmosphere has also a clear impact on the magnetic properties of the layers. The uniaxial in-plane magnetic anisotropy of the as-grown film evolves to magnetic isotropy when annealed at 600 °C probably due to the segregation and formation of Ga-rich areas. After Ga evaporates from the sample, Fe is fully oxidized and only a weak ferromagnetism related to Fe 2 O 3 is detected.

Electrodeposition of Hybrid Magnetostrictive/Magnetoelectric Layered Systems

“…Very recently, the inhibition of Fe oxidation has been shown when trying to electrodeposit GFO; indications of oxidation were only detected for Ga, whereas Fe remained in its metallic state [ 24 ]. This is in agreement with previous results obtained when studying the effect of thermal treatments in oxygen atmosphere on FeGa thin films [ 25 ]. In that work, while Ga was strongly oxidized and eventually evaporated as the oxidation temperature was raised, Fe remained in its metallic state.…”

Use of Ga2O3[1 0 0] monocrystals as substrates for the synthesis of GaFeO3 thin films

“…In a recent work, laser molecular beam epitaxy growth protocol was reported and based on the sequential deposition of Ga 2 O 3 and Fe layers followed by a thermal treatment [14]. However, exsitu oxidation in oxygen atmosphere using uncapped sputtered FeGa layers was unsuccessful [15]. The main complications observed in our previous work were: i) annealing promoted the evaporation of Ga after the formation of Ga 2 O 3 oxides whereas Fe mainly remained in its metallic state, and ii) large surface damages [15].…”

“…However, exsitu oxidation in oxygen atmosphere using uncapped sputtered FeGa layers was unsuccessful [15]. The main complications observed in our previous work were: i) annealing promoted the evaporation of Ga after the formation of Ga 2 O 3 oxides whereas Fe mainly remained in its metallic state, and ii) large surface damages [15]. Therefore, capped FeGa layers to reduce damage, and using Ga 2 O 3 as a substrate to enhance the Ga content in the oxidized layers might be a better strategy to obtain GFO films.…”