Hexagonal Barium Ferrite Films Research Articles

Aluminum doping hexagonal barium ferrite films with large perpendicular magnetic anisotropy and high remanence ratio

Aluminum doping hexagonal barium ferrite film with large perpendicular magnetic anisotropy (PMA) and high remanence ratio was prepared on Al2O3 substrate by post-annealing at high temperature. The crystal structure measurements have shown that the crystallinity and degree of orientation were improved by post-annealing at high temperature, while it happened the Al ions diffusion from the Al2O3 substrate into the ferrite film at 1100 °C of annealing temperature. The diffusion phenomenon is also confirmed by the distribution of elements in the cross-section which displays a wide and slow-changing region of Al element. The Al element diffusion gives rise to a decrease of saturation magnetization, and an increase of coercivity and remanence ratio. Generally, a hexagonal barium ferrite film with large PMA field (HA = 18.1 kOe), relatively small FMR linewidth (540 Oe) and high remanence ratio (86%) was obtained by annealing the film at 1100 °C, which shows potential applied in self-biased microwave devices.

High remanence ratio of aluminum substituted hexagonal barium ferrite films for self-biased microwave devices

A high remanence ratio of hexagonal barium ferrite film is urgently needed for self-biased microwave devices. In this work, the aluminum-substituted hexagonal barium ferrite films (BaFe(12−x)AlxO19) with different substituting concentrations (x = 0, 1.5, 2, 2.5, 3) were deposited on the Al2O3 substrate by pulsed laser deposition method using self-sintered BaFe(12−x)AlxO19 target. Firstly, the targets with different Al concentrations were sintered by the solid phase method and exhibited high dense, uniform microstructure, and high purity. Then, the influence of the Al ions concentration on the crystal structure, morphology, and magnetic and microwave properties of BaFe(12−x)AlxO19 films was studied in detail. Structural characterizations confirm that the Al prefers to substitute for 2a, 4f2 and 2b sites and promotes the grain (formed as single-domain) orientation growth, which results in a decrease in the saturation magnetization, an increase of remanence ratio and anisotropy field. Consequently, a high remanence ratio of 95 % was obtained for BaFe(12−x)AlxO19 film at x = 3, and also displays a high anisotropy field (27.7 kOe), a low saturation magnetization (1758 G) and an appropriate ferromagnetic resonance linewidth (～436 Oe), which can be applied in self-biased devices.

High Remanence Ratio of Aluminum Substituted Hexagonal Barium Ferrite Films for Self-Biased Microwave Devices

High Remanence Ratio of Aluminum Substituted Hexagonal Barium Ferrite Films for Self-Biased Microwave Devices

Effects of Crystal Structure, Morphology and Ion Diffusion During Annealing on Magnetic Properties of Hexagonal Barium Ferrite Films

Effects of Crystal Structure, Morphology and Ion Diffusion During Annealing on Magnetic Properties of Hexagonal Barium Ferrite Films

Stoichiometry, phase, and texture evolution in PLD-Grown hexagonal barium ferrite films as a function of laser process parameters

Barium hexaferrite (BaFe12O19 or BaM) films were grown on c-plane sapphire (0001) substrates by pulsed laser deposition (PLD) to evaluate the effects of laser fluence on their composition, structure, and magnetic properties. A Continuum Surelite pulsed 266 nm Nd:YAG laser was employed, and the laser fluence was varied systemically between 1 and 5.7 [J/cm2]. As the laser fluence changed the stoichiometric transfer between the BaM targets and deposited thin films were affected. The Fe to Ba ratio in the films increased with laser fluence. The films deposited at laser fluences below 4 J/cm2 showed undesirable 3-dimensional island growth. Moreover, an insufficient laser energy resulted in deposition of secondary phases corresponding to Barium monoferrite (BaFe2O4) and Magnetite (Fe3O4). Alternatively, laser fluences above 5 J/cm2 promoted resputtering of the growing film at the substrate and degraded film quality, structure, and magnetic properties. BaM films deposited at 4.8 J/cm2 - the optimal laser fluence - showed excellent c-axis orientation perpendicular to the film plane with an anisotropy field of 16 kOe and saturation magnetization of 4.39 kG. These results clearly demonstrate a strong influence of laser parameters on PLD-grown hexaferrite films and provide a path for high-yield production using pulsed laser depositions systems.

Film-Thickness Dependence of the Morphology, Crystal Structure and Magnetic Properties of BaFe12O19 Films Prepared by Pulsed Laser Deposition

In this work, hexagonal barium ferrite films were deposited on polished sapphire (0001) substrates by pulsed laser deposition. The dependencies of morphology, crystallinity and magnetic properties on film thickness were investigated in detail. The results from measurements revealed that the degree of orientation and surface roughness of films gradually deteriorated with increasing film thickness. Additionally, as the film thickness increased, the magnetic properties showed an obvious degradation, especially in terms of the saturation magnetization and magnetic anisotropy. Consequently, the results of this study further prove that the deposition of high-quality BaM films with large thickness is significant, while difficult.

Erratum to “Magnetic properties of hexagonal barium ferrite films on Pt/MgO(111) substrates annealed at different temperatures”[J. Magn. Magn. Mater. 413(2016) 25–29

Erratum to “Magnetic properties of hexagonal barium ferrite films on Pt/MgO(111) substrates annealed at different temperatures”[J. Magn. Magn. Mater. 413(2016) 25–29

Hexagonal barium ferrite films on a Pt(1 1 1)/Si(0 0 1) substrate and their local magnetic properties

Abstract Hexagonal barium ferrite films were deposited on Pt(1 1 1)/Si(0 0 1) substrates by pulsed laser deposition. This paper presents an investigation of the crystal structure, morphology and local magnetic properties of the deposited films. The characterization results demonstrated orientation and morphological dependences on the Pt thickness and annealing temperature. A film prepared with a 200-nm-thick Pt buffer layer and an annealing temperature of 900 °C exhibited oriented platelet grains with a mean diameter of ∼400 nm and excellent magnetic properties with a saturation magnetization of ∼311 emu/cm3, a uniaxial anisotropy field of ∼15.5 kOe and a remanent squareness in the out-of-plane direction of ∼68.6%. Furthermore, a first-order reversal curve (FORC) diagram showed that the film had a positive mean interaction field (Hu) between particles and broad distributions of coercivity (Hc) centred at Hu = 600 Oe and Hc = 2500 Oe.

Magnetic Properties of Hexagonal Barium Ferrite Films on Pt(111)/Al2O3(0001) Substrate Based on Optimized Thickness of Pt

In this study, hexagonal barium ferrite thin films have been deposited on Pt(111)/Al2O3(0001) substrates by pulsed laser deposition. The thickness of Pt dependence of crystallographic structure and magnetic properties has been studied. X-ray diffraction θ-2θ reveals the films have a good c-axis orientation perpendicular to the film plane. Furthermore, pole figure analysis discovers that the crystallinity of films is greatly improved by Pt buffer layer and the highest degree of orientation is prepared at 20-nm-thick Pt. It is also observed from scanning electron microscope and atomic force microscopy that the BaM film with 20-nm-thick Pt is formed as hexagonal shaped and has smaller than 2 nm of roughness. Magnetic hysteresis loops show the saturation magnetization ( ${\rm{M}}_{{\rm{s}}}$ ), coercivity ( ${\rm{H}}_{{\rm{c}}}$ ), and uniaxial anisotropy field ( ${\rm{H}}_{{\rm{k}}}$ ) are greatly depended on the thickness of Pt buffer layer. Consequently, films with 20-nm Pt buffer layer have the highest ${\rm{M}}_{{\rm{s}}}$ of ${\rm{358\,emu/ cm}}^{3}$ and ${\rm{H}}_{{\rm{k}}}$ of 16.7 kOe which are comparable with the theoretical value of BaM bulk.

Effect of Pt buffer layer on crystal structure and magnetic properties of hexagonal barium ferrite films

Hexagonal barium ferrite films have been deposited on Pt(111)/Al2O3(0001) substrates by pulsed laser deposition. The influence of Pt buffer layer on the crystal structure and magnetic properties of barium ferrite film has been studied. X-ray diffraction θ-2θ reveals the crystallization temperature of film is decreased by the 20nm-thick Pt buffer layer. Furthermore, pole figure analysis shows that the orientation of films is greatly improved by Pt buffer layer. Magnetic hysteresis loops represent the saturation magnetization (Ms) and uniaxial anisotropy field (Hk) are greatly depended on the Pt buffer layer. Consequently, BaM film with 20nm Pt buffer layer have Ms of 358emu/cm3 and Hk of 16.7kOe which are comparable with the theoretical value of BaM bulk.

Magnetic properties of hexagonal barium ferrite films on Pt/MgO(111) substrates annealed at different temperatures

In this work, hexagonal barium ferrite thin films have been deposited on Pt/MgO(111) substrates by pulsed laser deposition. The anneal temperature dependence of crystal structures, extents of diffusion and magnetic properties have been studied. X-ray diffraction patterns reveal that the crystal structure changes from the hexagonal to the spinel when the anneal temperature increases. The texture with c-axis perpendicular to the film plane and the small c-axis dispersion angles (△ɵc) have been obtained in the film annealed at 950 °C for 10h. Both the X-ray photoelectron spectroscopy profiles and energy dispersive spectrometer show that the diffusions of Mg2+and Fe3+cations are more obvious when the annealing temperature is higher than 950°C. The film annealed at 950°C show anisotropic and hard magnetic properties. The magnetic properties of film annealed at 1050°C are soft.

Radio-frequency magnetron sputter-deposited barium hexaferrite films on Pt-coated Si substrates suitable for microwave applications

Hexagonal barium ferrite films were deposited on Si (1 1 1) substrates by radio-frequency magnetron sputter deposition. The films exhibited strong c- axis perpendicular orientation benefiting from a Pt buffer layer. The results include measurements of crystallographic structure, magnetic domain structure, and magnetic and microwave properties for barium hexaferrite films with different thicknesses of Pt underlayers, revealing ferromagnetic resonance linewidths, Δ H = 400–600 Oe at 40–60 GHz. These results provide a viable pathway to realizing miniaturized microwave devices integrated with semiconductor device platforms.

Preparation and magnetic properties of hexagonal barium ferrite films using BaM nanoparticles

Barium ferrite (BaFe 12O 19—BaM) thick films have been synthesized using a spinning coating sol–gel process. The coating sol was formed from BaM powders dispersed in the BaM raw sol. XRD, SEM, EDX, vibrating sample magnetometer (VSM), and ac susceptometer, were employed to evaluate the structure, composition and magnetic properties of BaM thick films. The results indicated that a uniform and crack-free coating of BaM with ∼15 μm thickness can be produced with good deal of consistency. The perpendicular and in-plane coercivity had the same value of 5 kOe. The high coercivity is attributed to the magnetocrystalline anisotropy and grain size of the sintered BaM layer. Effective magnetic susceptibility in all measurements have linear variation with increasing dc field.

Variation in material parameters for hexagonal barium ferrite films on (111) magnesium oxide as a function of oxygen pressure

This work examines the material characteristics and magnetic properties of hexagonal M-type barium ferrite (BaFe12O19) films deposited by pulsed laser ablation deposition onto (111) magnesium oxide substrates at different oxygen growth pressures. X-ray diffraction data showed the lattice constant of the film grown at 300 mTorr c=23.23 Å increased to c=23.30 Å for the film grown at 20 mTorr. The saturation magnetization ranged from 4.03 to 4.33 kG and the magnetic uniaxial anisotropy field ranged from 16.73 to 19.49 kOe as the oxygen pressure was varied from 10 to 300 mTorr. The narrowest ferrimagnetic resonance (FMR) linewidths (ΔH) for as-produced films were obtained for the 10 mTorr films, where ΔH=0.39 kOe. Films grown with oxygen pressure at 200 mTorr or higher showed two distinct resonance modes, which exhibited ΔH1⩾0.90 kOe and ΔH2⩾1.10 kOe at 59 GHz for a film deposited at 925 °C. The FMR linewidths for this film decreased to ΔH1=0.52 kOe and ΔH2=0.45 kOe after annealing the film at 1000 °C for 1 h. These results indicate that thick films grown at higher oxygen pressures have magnetic parameters closer to bulk values, but also show larger magnetic losses than films grown at lower oxygen pressures.

Structural and ferromagnetic resonance characteristics of BaFe12O19 films with minimal linewidths

Hexagonal barium ferrite films with thickness between 0.3 and 8 μm were deposited on (0001) oriented Al2O3 using pulsed laser deposition and optimized growth and annealing conditions. They were characterized by measurements of x-ray diffraction, Rutherford backscattering, magnetization, atomic force microscopy and ferromagnetic resonance (FMR) at 58 GHz. The narrowest FMR lines and largest number of spin wave resonances are obtained when the field is perpendicular to the film plane of 0.3 and 0.46 μm films. To quantitatively account for variations with field angle (θ) we assume (i) a strain-induced anisotropy energy with cos4 θ dependence and (ii) that the film should be pictured as a mosaic whose tiles are tilted out of the film plane.

Mechanism of composition change in sputter deposition of barium ferrite films with sputtering gas pressure

In this study, we used computer simulation to investigate changes in the composition of hexagonal barium ferrite films with sputtering gas pressure obtained by the sputter-deposition processes. The iron content in the film deposited by facing target sputtering increased as the sputtering gas pressure increased and reached a maximum value at a certain gas pressure. These changes in the film composition were explained as follows: sputtered particles scatter when they collide with sputtering gas atoms, and this scattering changes the ratio of the particles reaching the substrate. When the substrate was located to the side of the target, as in a facing target sputtering system, this scattering resulted in an increase in the amount of sputtered particles arriving at the substrate, although too much scattering caused the amount to decrease. When a magnetron sputtering system is used for the film preparation, this gas scattering leads to a decrease in the amount of sputtered particles arriving at the substrate which is located opposite the target. Since this gas scattering depends significantly on the atomic mass of the sputtered particles, the gas pressure dependence of the amount of iron atoms arriving differs considerably from that of the amount of barium atoms arriving. This difference leads to the changes in film composition.

CHANGES IN THE COMPOSITION OF SPUTTERED BARIUM FERRITE FILMS AS A RESULT OF SCATTERING DUE TO THE COLLISION OF SPUTTERED PARTICLES AND SPUTTERING GAS

In this study, we used computer simulation to investigate changes in the composition of hexagonal barium ferrite films deposited by a facing target sputtering. The iron content in the film increased as the sputtering gas pressure increased and reached a maximum value at a certain gas pressure. These changes in the film composition were explained as follows; sputtered particles scatter when they collide with sputtering gas atoms, and this scattering changes a ratio of the particles reaching the substrate. When the substrate was located to the side of the target as in a facing target sputtering system, this scattering resulted in an increase in the amount of sputtered particles arriving at the substrate, although too much scattering caused the amount to decrease. Since this gas scattering depends significantly on the atomic mass of the sputtered particles, the gas pressure dependence of the amount of the iron atoms arriving differs considerably from that of the amount of barium atoms arriving. This difference leads to the changes in film composition.

Structure and magnetic properties of hexagonal barium ferrite films deposited by alternate layer deposition method

Deposition of c-axis perpendicularly oriented hexagonal barium ferrite thin films were formed by an alternate periodic deposition of S (Fe6O8) and R(BaFe6O11) layers. BaM film with excellent c-axis orientation and good crystallinity was obtained when S layers 4.7 A thick and Rlayers 6.9 A thick was deposited on a ZnO underlayer. To reduce the amount of the Zn ions diffusing from the ZnO underlayer to the BaM film, the thickness of the ZnO underlayer was reduced. An underlayer less than 10 nm thick, however, significantly degraded the c-axis orientation of the BaM films. We also tried to deposit BaM films on various kinds of underlayers such as α-Fe2O3 and amorphous barium ferrite (a-BaM). A BaM film with c-axis orientation was obtained only on a ZnO underlayer and an a-BaM/ZnO underlayer, although the c-axis of the BaM crystallites in the film deposited on a ZnO underlayer inclined about 2 degrees from the normal to the film surface.

Preparation and characterization of thin films of M-type barium ferrite on microcrystalline carbon substrates with diffusion barrier sublayers

Hexagonal barium ferrite films have been grown on microcrystalline carbon substrates for the first time and thermally oxidized SiO2/Si wafers using dc facing targets sputtering. Si3N4 and SiO2/Cr underlayers were effective in preventing carbon diffusion into the barium ferrite films during deposition at high temperatures (550–600 °C). X-ray diffraction spectra showed that the c axis of the crystals are perpendicular to the film surface. The dispersion of the c axis (Δθ50) was 2.5°. The perpendicular coercivity varied from 860 to 1200 Oe and the saturation magnetization (Ms) was about 300 emu/cm3. The delta M curves were negative in the in-plane direction and positive in perpendicular directions.