Surface Modification and Enhancement of Ferromagnetism in BiFeO3 Nanofilms Deposited on HOPG

Abstract

BiFeO3 (BFO) films on highly oriented pyrolytic graphite (HOPG) substrate were obtained by the atomic layer deposition (ALD) method. The oxidation of HOPG leads to the formation of bubble regions creating defective regions with active centers. Chemisorption occurs at these active sites in ALD. Additionally, carbon interacts with ozone and releases carbon oxides (CO, CO2). Further annealing during the in situ XPS process up to a temperature of 923 K showed a redox reaction and the formation of oxygen vacancies (Vo) in the BFO crystal lattice. Bubble delamination creates flakes of BiFeO3-x/rGO heterostructures. Magnetic measurements (M–H) showed ferromagnetism (FM) at room temperature Ms ~ 120 emu/cm3. The contribution to magnetization is influenced by the factor of charge redistribution on Vo causing the distortion of the lattice as well as by the superstructure formed at the boundary of two phases, which causes strong hybridization due to the superexchange interaction of the BFO film with the FM sublattice of the interface region. The development of a method for obtaining multiferroic structures with high FM values (at room temperature) is promising for magnetically controlled applications.

Synthesis of MIL‐53(Fe) Metal‐Organic Framework Material and Its Application as a Catalyst for Fenton‐Type Oxidation of Organic Pollutants

“…e XPS survey spectra of the samples (Figures 10(a) [1,5,24]. e peak separation, namely, ΔFe2p � 2p 1/2 − 2p 3/2 ≈ 13 eV, is very similar to the theoretical value of 13.6 eV for Fe 2 O 3 [38]. erefore, these peaks belong to Fe 3+ of the iron (III) benzene dicarboxylate samples.…”

Surface morphology and X-ray photoelectron spectroscopy of BiFeO3 thin films deposited on top of Ta2O5/Si layers

“…The source for bismuth component was Bi(mmp)3 and ferrocene was the source of iron Fe(C5H5)2. The experiment was repeated in accordance with the preparation of thin BFO films in our previous experiments on the substrate surface of highly oriented pyrolytic graphite [12,13] and TiO2 nanotubes [9,10]. In this work, Ta2O5/Si heterostructures were used as substrates [14] with thickness of Ta2O5 from 20 up to 100 nm.…”

Crack resistance of bismuth ferrite films obtained on a flexible substrate

“…The experiment was repeated similarly to obtain thin films of bismuth ferrite on the surface HOPG [20,21] and TiO2 [22,23]. Figure 1 shows optical images of the surface of the obtained films, depending on the increase in the concentration of bismuth in the film: sample 1 is a stoichiometric composition, sample 2 contains a slight higher concentration of bismuth.…”

“…Some of the more important among them is coupled magnetic ordering, giving it both ferroelectric and antiferromagnetic properties, including large remnant ferroelectric polarization, potentially greater than other commonly used ferroelectric materials [1][2][3]. When the absence of lead and the ability to keep its properties in room temperature and very thin films (in the range of units of nanometers), are added into the consideration, BFO shows its incredible potential for ferroelectric, magnetoelectric, and piezoelectric applications [4][5][6].…”