Reactively sputtered half-metallic Fe3O4 thin films at room temperature on polymethyl methacrylate: A perspective for flexible spintronics

For plastic spintronics, it has thus far been a challenge to develop a (magnetic nanostructures)/polymer heterostructure at low temperature due to the thermal sensitivity of polymers. In this context, half-metallic magnetite (Fe3O4) films of different thicknesses were coated on flexible polymethyl methacrylate (PMMA) substrates by reactive sputtering at 300 K. Grain size and thickness increased from ~10 nm to ~34 nm and 50 nm to 400 nm with an increase in the deposition time from 165 to 1335 s, respectively. Moreover, a sharp rise in grain size was observed when the thickness of the film reached 200 nm, and finally, saturation took place at 400 nm. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS) studies confirmed the absence of the γ-Fe2O3 phase and thus the successful deposition of Fe3O4 thin films on the PMMA substrate. Parameters as such as Verwey transition (T v ) (~125 K), saturation magnetization (M s ) (~354 emu/cm3) and magnetoresistance (MR) (−8.6% under 60 KOe at 300 K) under H ∥ Film plane were obtained for Fe3O4/PMMA heterostructures with a film thickness of 200 nm. The resistivity (ρ), T v , M s and MR were hardly affected on several bending tests, proving that Fe3O4/PMMA heterostructures are exciting materials for future flexible spintronics.