Ferrite Thin Films Research Articles

Strong Dependence of Magnetic Damping and Magnetization on Deposition Temperature in Highly Magnetostrictive NiZnAl Ferrite Thin Films

Zn/Al co-doped nickel ferrites (NZAFO) with ultralow magnetic damping and large magnetostriction are critically needed for use in tunable spintronic devices and dissipationless quantum computation. However, the growth of epitaxial NZAFO thin films with optimized properties is difficult due to their tendency to form anti-site defects and antiphase boundaries, even on isostructural spinel substrate. Here, growth temperature-dependent ferromagnetic resonance (FMR) and magnetization have been systematically investigated. The saturate magnetization and damping linewidth have decreased from 114 to 70 emu/cc and 321 to 12 Oe as deposition temperature increased from 500 °C to 650 °C, respectively. With further optimization of the film thickness, a minimum FMR linewidth of 7.5 Oe has been observed, only 1.74% of that of bulk form NZAFO materials. Further increasing of deposition temperature to 700 °C results in a dramatic increase in the magnetic coercive field and damping linewidth. The magnetostriction and magnetocrystalline anisotropy are relatively stable in a large temperature range. The strong dependence between magnetic properties and the deposition temperature has been explained in terms of cation redistribution and evaporation. The insulating ferrimagnetic NZAFO with ultralow microwave loss and strain tunable static and dynamic magnetic properties serve as a promising candidate to be used in various tunable electronic devices.

Low‐cost Fabrication of Zn‐doped MnFe2O4 (Mn0.5Zn0.5Fe2O4) Film for H2S Gas Sensing Applications

AbstractMulticomponent spinel ferrites are essential to be used in high‐performance gas‐sensing materials. In the present work, Mn0.5Zn0.5Fe2O4 spinel ferrite thin film is prepared via spray printing technique. The prepared film can be easily retrieved and utilized for multiple cycles due to its magnetic properties. The morphology, composition, and crystal structure of Mn0.5Zn0.5Fe2O4 spinel ferrite thin film are examined using scanning electron microscopy, infrared spectroscopy, and X‐ray diffraction. The produced films are in the range of around 20 nm and manifest spinel cubic structure. The prepared film is tested for its sensitivity to NO2, NH3, H2, and H2S gases, and the Mn0.5Zn0.5Fe2O4 spinel ferrite thin film is found the most sensitive and selective to H2S gas. The prepared Mn0.5Zn0.5Fe2O4 spinel ferrite thin film shows enhanced sensing performance functional at low temperatures, and consequently, they need low operational power. They are also simple to fabricate at the appropriate cost.

Strain Engineering of Magnetic Anisotropy in Epitaxial Films of Cobalt Ferrite (Adv. Mater. Interfaces 23/2021)

Strain Engineering of Magnetic Anisotropy In article number 2101034, Hiroshige Onoda, Hideto Yanagihara, and co-workers demonstrate that the strain engineering technique is a promising way to induce large magnetic anisotropy without using heavy metals or rare earth elements. The spins (red arrows) of Co ions (light blue) on the octahedral sublattice of the spinel structure change their preferred direction in response to the epitaxial stress of the cobalt ferrite thin film due to the change in the orbital moment.

Effect of Cu and Sm doping on the ferroelectric character of bismuth ferrite thin films

This report discusses the effect of substitution of copper (Cu) and samarium (Sm) at the Fe-site and Bi site respectively on structural, morphological, optical and ferroelectric properties of bismuth ferrite (BiFeO3) films. Pure and (Sm, Cu) co-doped perovskite BiFeO3 thin films were fabricated on fluorine doped tin oxide substrates by sol–gel assisted spin coating technique. The X-ray diffraction analysis revealed the rhombohedral structure of all the samples. This confirmed that no phase change occurred due to doping. The atomic force microscopy (AFM) images of the films present uniform distribution of grains. The UV–Vis spectra demonstrated increased absorption for the doped samples. The corresponding Tauc plots exposed reduction in the energy bandgap of the doped films. The ferroelectric studies exhibited significantly improved saturation polarization, remnant polarization and coercive field of the doped films. The reduced band gap in the visible region and enhanced ferroelectric behavior of (Sm, Cu) co-doped bismuth ferrite films favor their suitability in visible light photovoltaic applications.

Effect of doping in multiferroic BFO: A review

Bismuth ferrite (BFO) nanostructures and thin films have gained attraction as suitable candidates for energy storage and energy conversion due to their high energy storage efficiency, temperature stability and low dielectric loss. Electrical properties of such multiferroic materials are tailored by ferroelectric and ferromagnetic constituents and have opened up amazing avenues in electrochemical supercapacitor and photovoltaic applications. Dopants play a significant role in optimizing the magnetic and dielectric properties of such materials owing to suitable applications. This review highlights the scientific advancements reported in BFO nanostructures for energy applications by optimizing their magnetic and dielectric properties. This paper starts with a brief introduction of BFO and a discussion on the effects of various dopants by different synthesis techniques, and their effects on the magnetic and dielectric properties are also portrayed. Eventually, this review summarizes the various doping effects, which paves way for future research on this multiferroic material.

Multiple spintronic functionalities into single zinc-ferrous ferrite thin films

The ability to combine multiple spintronic properties in the ZnxFe3-xO4 system with different variants of its chemical composition offers a new and tantalizing route towards homodevices. This is mainly due to the advantage of varying the Zn component of ZnxFe3-xO4, which leads to the possibility of preserving spinel symmetry (within 5% lattice mismatch) while changing the material properties from a ferrimagnetic half-metal (x = 0) to an insulating paramagnet (x = 1). Here we demonstrate that ZnxFe3-xO4 thin films, grown from a ZnFe2O4 single phase target, laser-ablated under a reduced atmosphere, exhibits a reduction of Zn content, a large 4πMS (6.5 kG), very low resistivity (25 mΩ cm) and a Verwey transition, all of which can be engineered by an appropriate choice of growth temperature. All these spectacular properties are confirmed by ab initio calculations and can be attributed to the inverse structure of [Znx+2Fe1−x+3]A[Fe1+y+3Fe1−y+2]BO4-δ, where the reduced Fe+2 ions along with Fe+3 occupy the octahedral sites while the Zn+2 and inverted Fe+3 sit in the tetrahedral sites. Phase formation in laser ablated ZnxFe3-xO4 thin films are different compared to the bulk thermal equilibrium, and shows that there is a competition between the reduction of Zn and the formation of O vacancies at various growth temperature zones.

Study of optical and magnetic properties of Mn-substituted bismuth ferrite thin films

Study of optical and magnetic properties of Mn-substituted bismuth ferrite thin films

Optoelectronic Functionality of BiFeO3–SrTiO3 Interface

AbstractOne effective way to extend the functional degree of freedom for semiconductors is to introduce structural defects (e.g., surface or interface) and chemical defects as they commonly exist and modify the properties of the entity. Here, the optoelectronic properties of bismuth ferrite thin films and their tuning by the interface between the film and the strontium titanate substrate are reported. The defects that have been demonstrated, especially oxygen vacancies, are of paramount importance in the photoelectric properties of a film‐substrate system. A detailed analysis of the oxygen vacancy levels supports the role of the interface in carrier transport. These results provide a new strategy to design the optoelectronic device via usual defect doping and interface coupling.

Electronic structure of nickel ferrite thin films growth on strontium titanate

In this study nickel ferrite thin films have been grown on strontium titanate-100 single crystal substrate by using RF magnetron sputtering. To investigate the electronic structure of nickel ferrite film, X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy were employed. In the X-ray photoelectron spectra of Fe 3p, the presence of the valence states Fe2+ and Fe3+ was evidenced; also, Ni2+ and Ni3+ were identified in the Ni 3p spectra. The atomic ratio of 2.01 was found, which is agreeing to the nominal atomic ratio. By reflection electron energy loss measurements found a band gap between 1.77 eV. The magnetic properties were analyzed by vibrating sample magnetometry, indicating in-plane easy magnetization.

Chemical Vapor Deposition of Cobalt and Nickel Ferrite Thin Films: Investigation of Structure and Pseudocapacitive Properties

AbstractTransition metal ferrites, such as CoFe2O4 (CFO) and NiFe2O4 (NFO), have gained increasing attention as potential materials for supercapacitors. Since chemical vapor deposition (CVD) offers advantages like interface quality to the underlying substrates and the possibility for coverage of 3D substrates, two CVD processes are reported for CFO and NFO. Growth rates amount to 150 to 200 nm h−1 and yield uniform, dense, and phase pure spinel ferrite films according to X‐ray diffraction (XRD), Raman spectroscopy, Rutherford backscattering spectrometry and nuclear reaction analysis (RBS/NRA) and scanning electron microscopy (SEM). Atom probe tomography (APT) and synchrotron X‐ray photoelectron spectroscopy (XPS) give insights into the vertical homogeneity and oxidation states in the CFO films. Cation disorder of CFO is analyzed for the first time from synchrotron‐based XPS. NFO is analyzed via lab‐based XPS. Depositions on conducting Ni and Ti substrates result in electrodes with pseudocapacitive behavior, as evidenced by cyclovoltammetry (CV) experiments. The interfacial capacitances of the electrodes are up to 185 µF cm−2.

Structural, Optical and Magnetic Properties of Diamagnetic Cd2+ Incorporated Cobalt Ferrite Thin Films Deposited by Spray Pyrolysis

Structural, Optical and Magnetic Properties of Diamagnetic Cd2+ Incorporated Cobalt Ferrite Thin Films Deposited by Spray Pyrolysis

Control of Magnetic Properties of Barium Ferrite Thin Films With Unusual Valence Fe

Thin films of BaFe1-xMxO3 (M = Hf, Zr, and Ce; 0.0 ≤ x ≤ 0.75) were fabricated using pulsed laser deposition and their magnetic properties were investigated. X-ray diffraction analysis indicated that oxygen-deficient BaFeOx (x < 3.0) with a monoclinic structure was formed when the deposition was conducted using a non-substituted target (x = 0.0). The as-grown BaFeOx films were converted into fully oxidized BaFeO3 with a perovskite structure by low-temperature oxidation in an ozone atmosphere. In contrast, the as-deposited films of Hf, Zr, and Ce-substituted films exhibited a perovskite structure, and their crystallinity did not change after low-temperature ozone annealing. The magnetic transition temperature Tc of the BaFeO3 film was 115 K, whereas the substituted BaFeO3 films showed ferromagnetic behavior even at 300 K. These results can be attributed to the weakening of the antiferromagnetic super-exchange coupling among Fe ions owing to the lattice expansion in the substituted BaFeO3. In addition, the magnetization of the films was found to increase with the decreasing ionic ratio of Fe4+/Fe3+, suggesting that the inherent carrier-induced ferromagnetic interaction is dominant in the films.

High temperature treatment of epitaxial nickel ferrite thin films: The way to bulk-like magnetic properties

An appropriate choice of growth conditions has made feasible fabrication of thin epitaxial NiFe2O4 / SrTiO3 films with parameters close to those of bulk nickel ferrite. Spin waves with a damping parameter as low as 10-2 and a very narrow ferromagnetic resonance line were observed in the samples subjected to post-growth high temperature annealing in oxygen. The analysis of electron and X-ray diffraction has shown substantial improvement of the crystalline quality of the annealed films. X-ray absorption spectroscopy and X-ray magnetic circular dichroism data simulation have revealed that the films exhibit a completely inverted spinel structure characterized by the maximal possible net magnetic moment.

Complementary study of anisotropic ion conduction in (110)-oriented Ca-doped BiFeO3 films using electrochromism and impedance spectroscopy

Oxygen vacancies are ubiquitous in oxides, and taking advantage of their mobility is the cornerstone for a variety of future applications. The visualization and quantification of collective defect flow based on electrochromism is a powerful approach to explore oxygen kinetics and electrochemical reaction even in cases that electronic conduction is considerably mixed, but whether or not the measured kinetic properties harmonize with those obtained by the conventional impedance spectroscopy remains veiled. Here, we identify complementary relationships between the two methods by investigating the oxygen vacancy transport in Ca 30%-doped bismuth ferrite thin films epitaxially grown on SrTiO3 (110) substrates. We find that the activation energy of ionic hopping is 0.78 (or 0.92 eV) for the application of an electric bias along [001] (or [11¯0]) due to the grain elongation along [001]. We anneal the films in an N2 gas environment at high temperatures to suppress the electronic contribution for access to standard impedance spectroscopy. The oxygen kinetic properties obtained from the two methods are consistent with each other, complementarily revealing the collective phase evolution as well as the ionic impedance of the bulk, grain boundary, and interfacial regions. These comparative works provide useful insights into ionic defect conduction in oxides in an intuitive and quantitative manner.

Influence of Gd doping and thickness variation on structural, morphological and optical properties of nanocrystalline bismuth ferrite thin films via sol–gel technology

Influence of Gd doping and thickness variation on structural, morphological and optical properties of nanocrystalline bismuth ferrite thin films via sol–gel technology

Anneal temperature dependence of resistive switching and photoelectric properties of Bismuth ferrite thin film prepared via sol–gel method

Enhancement on resistive switching characteristics of Bismuth ferrite (BFO) has attracted persistent interest in the past decades due to the inimitable interior structure. In the work, the amorphous and the polycrystalline Bismuth ferrite thin films have been successfully prepared via sol–gel method. We utilize X-ray diffraction, Transmission Electron Microscope and absorption spectrum to characterize the internal structure and calculate the band gap of Bismuth ferrite thin film samples. By comparing the current–voltage (I-V) characteristics between the amorphous and the polycrystalline sample, we investigate the amorphous sample has better resistive switching performance (switching ratio is 104) than that of polycrystalline (101) bismuth ferrite thin film devices. However, the polycrystalline Bismuth ferrite sample exhibits favorable switchable photovoltaic response and good stability. Additionally, we discuss the conduction mechanism via the double logarithm fitting of amorphous Bismuth ferrite sample. The article also indicates that resistive switching property is closely related with the defects such as oxygen vacancies. The article deepens the comprehension of resistive switching properties of amorphous and polycrystalline Bismuth ferrite thin film which would have further potential applications in advanced electronic devices such as new resistive memory.

Low-temperature solid-phase pyrolysis: A new method for the synthesis of nanocrystalline NiFe2O4 thin films

Nickel ferrite thin films were synthesized by a new method of solid-phase pyrolysis. The effect of the annealing temperature on the films characteristics has been studied. The obtained films were characterized by X-ray diffraction (XRD), thermal and thermogravimetric analysis (TG-DTA), and scanning probe microscopy (SPM). XRD showed a single-phase cubic spinel structure. The average size of NiFe2O4 crystallites was 28, 30, 42, and 53 nm for samples annealed at 500, 600, 700, and 800 °C, respectively. The films thickness is about 40 nm. The SPM data confirm a high-quality of the film surface, formed by nanocrystallites. The obtained films are well organized, which makes the proposed as a promising method of synthesis in the thin films preparation processes employed in a variety of applications.

Spray deposited multimetal Cu-Ni-Zn ferrite for gas sensing application

In this work, nanocrystalline Cu-Ni-Zn ferrite thin films were deposited by the cost-effective spray pyrolysis technique and characterized for structural, elemental, morphological, and gas sensing properties. The XRD confirmed the nanocrystalline nature of the film. The morphology of the sample was found with surface pores as a consequence of porogen activity. The deposited material was found better responding to SO2 gas. The optimal operating temperature of the sensor was found 120 ℃. This operating temperature is much lower than earlier reported SO2 gas sensors. At optimal operating temperature, it showed linear response up to 50 ppm of gas exposure.

Structure and dielectric properties of thin nanocrystalline ZnFe2O4 films

Optically transparent high-quality nanosized crystalline zinc ferrite thin films on different substrates have been synthesized by the decomposition of organic zinc and iron (III) compounds. According to scanning probe microscopy study, the films are 40-50 nm thick and their surface consists of densely spaced uniformly oriented crystallites with morphology depending on the substrate. X-ray diffraction analysis has shown that the films are polycrystalline and ZnFe2O4 has a cubic spinel structure. The dielectric constant lies in the range of 53 ÷ 54. The films are spontaneously polarized with a residual polarization of about 0.59 ÷ 0.69 μC⋅cm−2 , the coercive field is (8 ÷ 12)·104 V/cm.

Diverse physical characteristics of mixed Li–Mg spinel ferrite thin films fabricated by spray pyrolysis technique

Nanocrystalline Li0.5-x/2MgxFe2.5-x/2O4 (0.0≤x ≤ 1.0) thin films have been effectively fabricated by spray pyrolysis technique. These films show monophase cubical construction as appeared in the XRD patterns and also validated by FTIR spectroscopy. The optical energy band gap values were obtained in the range of 1.78–2.52 eV. The excitation wavelengths were found to be in between 400 and 410 nm which attributed to the holes and electron in photoluminescence spectra. VSM results reveal that magnetic parameters lowered with Mg2+-substitution in Li0·5Fe2·5O4. The incorporation of Mg2+-substitution in pristine lithium ferrite thin films promotes the tailoring of the structural, optical and magnetic properties.