NiZn Ferrite Films Research Articles

High Deposition Rate Obtained for Spin-Sprayed Ni-Zn Ferrite Films Without Using Ammonia Ions

Spin-spray ferrite plating without using corrosive ammonia ions was developed and very high deposition rate of 60 nm/min of Ni-Zn ferrite films was achieved by spraying the reaction solution (FeCl/sub 2/+NiCl/sub 2/+ZnCl/sub 2/) and oxidizing solution (NaNO/sub 2/+KOCOCH/sub 3/) on the rotating glass substrate at 90/spl deg/C. The change of pH buffer from (NH/sub 4/)OCOCH/sub 3/ to KOCOCH/sub 3/ increased the pH in oxidizing solution from 6.8 to 7.6 and this higher pH expedited the ferrite film formation. The film surface observed in SEM image was smooth, and a large saturation magnetization M/sub s/ of 420 emu/cc and low coercivity H/sub c/ below 25 Oe were obtained. This film exhibited a high real permeability /spl mu/'/sub r/=45 and a high ferromagnetic resonance frequency f/sub r/=500 MHz. The deposition rate increased to 73 nm/min by increasing pH in oxidizing solution from 7.6 to 12.0. Although the film was porous, very high deposition rate of 230 nm/min was obtained for the film using oxidizing solution with high pH of 12.4. This film exhibited /spl mu//sub r/'=15 and f/sub r/=1 GHz, which were comparable to those of commercialized conducted noise suppressors.

Growth and magnetic properties of soft ferrite films by pulsed laser deposition

Polycrystalline NiZn-ferrite films have been fabricated on Si(1 1 1) and glass substrates by pulsed laser deposition (PLD). XRD patterns indicate that an obviously preferential (4 0 0) orientation appears in the films deposited on a Si substrate, which may be related to the stress during growth. The thickness and growth of the films are investigated at different deposition temperatures and pressures. The observed mean grain sizes in all samples studied are below 70 nm, much smaller than the theoretically estimated single-domain size D c lower =113 nm. The experiment demonstrates that the saturation magnetization and coercivity are strongly dependent upon oxygen pressure, which implies that the cation distribution, defects and stress are dominantly responsible for magnetic properties. Particularly, it is considered that the stress has a significant influence on coercivity as oxygen pressure changes. Finally, the effect of annealing is also discussed.

Study on initial permeability of Ni–Zn ferrite films prepared by the spin spray method

Initial permeability of Ni–Zn ferrite films prepared by spin spray chemical plating is investigated. They exhibit a semi-hard magnetization process but have relatively high permeability with explicit dual peak resonance loss in the GHz frequency range. In this study, it turned out that the loss is determined mainly by the two magnetic parameters, namely, the crystalline anisotropy and a uniaxial anisotropy induced by Co addition. Measurement of permeability in an external DC field clarified that the semi-hard wall coercivity fixes the spin direction of residual magnetization state and, consequently, gives rise to uniaxial permeability with dependence of its direction on the previously applied DC field.

The structure and magnetic properties of Ni-Zn ferrite films

Ni-Zn ferrite films were fabricated by alternatively sputtering method. The effects of composition and fabrication conditions on Ni-Zn ferrite films were investigated. It is indicated that the as-deposited films were amorphous, but after annealing in air at different temperatures the spinel phase was formed and the main peaks were (311) peaks. In additional, after the investigation of the effects of different conditions on Ni-Zn ferrite films, the optimum conditions, was obtained for growth of Ni-Zn ferrite films.

スパッタ法で作成したＭｎ，ＭｎＺｎ，ＮｉＺｎ，およびＣｏフェライト薄膜のキュリー温度と飽和磁化

The Curie temperature and saturation magnetization of as-deposited Mn, MnZn, NiZn, and Co ferrite thin films by sputtering were different from those of heat-treated films at 700°C-900°C. After heat treatment, Curie temperature and saturation magnetization of Co ferrite thin films were invariable, whereas those of Mn, MnZn, and NiZn ferrite thin films depended on the heat treatment temperature. In the case of the ferrite thin films containing Mn and Zn, these results are explained by a nonequilibrium ion distribution, but another cause must exist in the case of the Co ferrite thin film. As-deposited sputtered ferrite thin films show nonequilibrium phenomena in both Curie temperature and saturation magnetization, whose cause is considered to depend on the ion content.

Ferromagnetic resonance study on magnetic homogeneity in spin-sprayed NiZn ferrite films highly permeable at gigahertz frequencies

Ferromagnetic resonance (FMR), including standing spin-wave resonance (SWR) modes, were measured in NiZn ferrite films, which have high permeability even up to the gigahertz range. They were prepared from an aqueous solution by spin spray ferrite plating at 90/spl deg/C. The perpendicular field FMR spectra exhibited SWR modes whose line separation had linear dependence on spin wave number, deviating from the quadratic behavior. This indicated that the films have inhomogeneous distribution of magnetization perpendicular to film plane, and have different magnetic surface anisotropies between the inner and outer surfaces of the respective films. The in-plane field FMR spectra revealed no SWR mode. A possible model is proposed to explain the features not only of the FMR spectra, but also of the initial permeability spectra measured on the films.

In-plane magnetic anisotropy induced in spin-sprayed Ni-Zn-Co ferrite films exhibiting strong magnetic loss at gigahertz range

Ni-Zn(-Co) ferrite films of 0.5-0.6 /spl mu/m in thickness were deposited on glass substrates by the spin-sprayed ferrite plating at as low as 90/spl deg/C applying external magnetic field of 50 Oe. Under no bias field, while the film without Co substitution (Ni/sub 0.21/Zn/sub 0.27/Fe/sub 2.52/O/sub 4/) exhibited a relatively high coercivity H/sub c/ of about 27 Oe, it decreased to 15 Oe for Co substituted film (Ni/sub 0.21/Zn/sub 0.27/Co/sub 0.04/Fe/sub 2.48/O/sub 4/), and a slight uniaxial anisotropy was induced along the liquid flow direction of sprayed solutions. The decrease in H/sub c/ was attributed to the anisotropy compensation originated by Fe/sup 2+/ and Co/sup 2+/. Under bias field of 50 Oe, a definite in-plane magnetic anisotropy was induced in the Co substituted film. The imaginary permeability /spl mu/'' was greater than 20 over a wide frequency range from 300 MHz to 3 GHz. Since the product of /spl mu/''/spl times/f, which is proportional to the absorption of conducted noise, increased even in gigahertz range reaching the peak at 1.7 GHz, Ni-Zn-Co ferrite films with in-plane uniaxial anisotropy are applicable as shielding materials for suppressing electromagnetic interference in gigahertz range.

Conducted noise suppression effect up to 3 GHz by NiZn ferrite film plated at 90 °C directly onto printed circuit board

A NiZn ferrite film (3 μm thick) was deposited at 90 °C by the spin-spray ferrite plating from an aqueous solution onto a 50 Ω microstrip line formed on an epoxy printed circuit board (PCB). A strong magnetic loss was caused by the ferrite film in a GHz range, ΔPloss reaching 67% attenuation at 3 GHz, the upper limit of our measurement. Furthermore, the reflection loss was very weak, S11 being smaller than 7%. Thus plated NiZn ferrite films hold strong promise to be actually applied to a type of thin film electromagnetic noise suppressors; the films can be directly deposited onto noise sources (semiconductor elements or electronic circuits) to attenuate conducted-electromagnetic noises in the GHz range. Because the plated NiZn ferrite film was magnetically isotropic in film plane, the noise suppressors will be isotropic, attenuating noise electromagnetic waves radiated from any directions. The NiZn ferrite film was also plated on a flat glass substrate as a standard, which exhibited natural resonance frequency of fr=500 MHz and initial real permeability of μ′=50. Compared to these values, the film on the PCB had higher fr of 850 MHz, though reduced in μ′ to 40. But the spectrum of the imaginary permeability μ″ shifted to a higher frequency range. This facilitated the strong magnetic loss at the high frequencies. The higher fr for the film on the PCB may be attributed to the undulated columnar structure of the film which was observed by scanning electron microscopy.

High-frequency transport properties of spin-spray plated Ni–Zn ferrite thin films

The frequency and temperature variation of magnetoimpedance in Ni–Zn ferrite thin films fabricated by spray plating method were studied. It is observed that the frequency induces a metal–insulator crossover behavior in impedance spectra. The frequency behavior of the electrical properties of the film can be modeled by an equivalent circuit composed of resistance and capacitance. The relaxation time and activation energy of the conductivity were calculated. The result suggests that the high-frequency conductivity of the spin-spray plating of a Ni–Zn ferrite film is predominantly associated with the dielectric, rather than by magnetization, dynamics. Mechanisms underlying high-frequency transport are discussed.

Magnetization and Curie Temperature of As-deposited NiZn Ferrite Thin Films by Sputtering and Changes in Them by Heat Treatment

Magnetization and Curie Temperature of As-deposited NiZn Ferrite Thin Films by Sputtering and Changes in Them by Heat Treatment

反応性ＥＣＲスパッタリング法によるＮｉ‐Ｚｎフェライト薄膜の低温作製

A novel sputtering method using an electron-cyclotron-resonance (ECR) microwave plasma was used to perform reactive sputter-deposition of Ni-Zn ferrite thin films. Ni-Zn spinel ferrite thin films with preferential orientation of (400) and relatively low coercivity of 15 Oe were obtained at a high deposition rate of 14 nm/min. and at temperatures lower than 200°C. To achieve this high deposition rate, the configuration of the ECR sputtering apparatus and processing parameters such as the microwave input power, target voltage, and oxygen partial pressure were carefully optimized. Reactive ECR sputtering is one of the most suitable methods for preparation of ferrite thin films applicable to magnetic devices such as MMICs isolators and circulators.

High-rate low-temperature (90°C) deposition of Ni-Zn ferrite films highly permeable in gigahertz range

Ni-Zn ferrite films have been prepared by spraying a reaction solution of FeCl/sub 2/ + NiCl/sub 2/ + ZnCl/sub 2/ (pH = 6.8) and an oxidizing solution of NaNO/sub 2/ + CH/sub 3/ COONH/sub 4/ + NH/sub 4/ OH (pH = 6.8-9.2) simultaneously onto rotating glass substrates at a substrate temperature of 90/spl deg/C. The deposition rate increased with the pH value of the oxidizing solution, and a maximum deposition rate of 67 nm/min was attained at pH = 8.4. The film surface observed by scanning electron microscopy was smooth, and a high value of saturation magnetization M/sub s/ = 482 emu/cm/sup 3/ with a low value of coercivity H/sub c/ = 17 Oe were measured. The film showed a high static permeability /spl mu/' = 70 and very high magnetic resonance frequency f/sub T/ of about 900 MHz. The imaginary part of the permeability /spl mu/ was greater than 30 over a wide frequency range from 300 MHz to 3 GHz. Ni-Zn ferrite films prepared in this study should be useful not only for planar inductors but also as shielding materials for electromagnetic interference suppressions.

Preparation of NiZn Ferrite Thin Films by a Spray Pyrolysis Deposition Method

Preparation of NiZn Ferrite Thin Films by a Spray Pyrolysis Deposition Method

Ni-Zn-Co ferrite films prepared at 90°C having μ"=30 at 3 GHz

Ni-Zn-Co ferrite films (Ni/sub 0.16-0.21/Zn/sub 0.30-0.36/Co/sub x/ Fe/sub 2.38-2.46/O/sub 4/, x=0/spl sim/0.16) were deposited by spin-spray ferrite plating method at low temperature of 90/spl deg/C. All the films had a saturation magnetization M/sub s/ larger than 440 emu/cc. A small amount of Co substitution x into Ni-Zn ferrite films changed the magnetic anisotropy in film plane from isotropic to anisotropic and the magnetic easy axis was parallel to the flowing direction of the sprayed solutions on the rotating substrate. The coercivity H/sub c/ and anisotropy field H/sub k/ took small values of 10 and 25 Oe at x=0.03. The complex permeability was measured in the range 20 MHz-3 GHz and very high static permeability /spl mu/' of 120 and resonance frequency f/sub r/ of 900 MHz were achieved at x=0.03. Exhibiting large /spl mu/">30 even at 3 GHz, this Ni-Zn-Co ferrite film is applicable for wave absorbers to suppress the electro-magnetic interference among devices up to microwave frequencies.

Elastic Behaviour and Internal Friction Studies on Ni-Zn Ferrite Films Prepared by Using the Pulsed Laser Ablation Method

The Ni-Zn ferrite thin films were prepared using the pulsed laser ablation method. The prepared films were characterized using X-rays. The magnetic properties were measured using the VSM. The elastic behaviour and internal friction studies were carried out using the composite piezoelectric oscillator method in the temperature range of 300-600 K. It was found that the value of Young's modulus decreases with increasing temperature and shows an anomalous behaviour in the vicinity of the Curie temperature. The value of internal friction for the present ferrites increases continuously with temperature up to the Curie point and a narrow maximum was observed just below the Curie temperature. It was found that the anomalous behaviour observed in the temperature variation of Young's modulus and internal friction disappears by the application of a magnetic field equal to the saturation field (380 mT) of the specimen under investigation. The observed anomalous behaviour in the vicinity of the Curie temperature was understood with the help of the temperature variation of the magneto-crystalline anisotropy energy (k) and Landau's theory.

Ni–Zn ferrite films with high permeability (μ′=∼30, μ″=∼30) at 1 GHz prepared at 90 °C

Ni–Zn ferrite films were prepared by spin-spray ferrite plating method at 90 °C on glass substrates from a reaction solution of FeCl2(+FeCl3)+NiCl2+ZnCl2 and an oxidizing solution of NaNO2+CH3COONH4. The complex permeability μ=μ′−iμ″ values of the as-plated films were measured at frequencies up to 3 GHz. The Ni0.28Zn0.18Fe2.54O4 film 0.40 μm in thickness plated using the mixture of Fe2+ and Fe3+ as iron ions exhibited a high μ′ of around 42 and a resonance frequency fr of 1.2 GHz. This fr value is about nine times as high as the 130 MHz that was estimated from Snoek’s limit for the Ni–Zn ferrite bulk ceramics. Since μ′ also exhibited a maximum value of about 35, the films prepared in this study will be applicable to both rf inductors and wave absorbers for electromagnetic interference suppression.

Anomalous variation of coercivity with annealing in nanocrystalline NiZn ferrite films

The sputter deposited NiZn ferrite thin films were studied as a function of annealing temperature. The magnetization showed a monotonic increase with increasing annealing temperature. The coercivity shows a minimum at annealing temperature of 400 °C and shows a value of 14 Oe. Transmission electron microscopy study indicated that the grain size increases from ∼3 nm for the as-deposited case to ∼15 nm for the film annealed at 800 °C. The observed coercivity behavior could be attributed to the defects present in the films, the change in cation distribution, and the grain growth.

Preparation and Characterization of NiZn Ferrite Thin Films by a Spray Pyrolysis Deposition Method.

Nickel-zinc (NiZn) ferrite thin films were successfully prepared from nickel, zinc, and iron nitrates aqueous solutions at a substrate temperature between 350 and 500°C in air by a spray pyrolysis deposition method (SPD), where the film thickness was held at about 1μm and the deposition rate was varied between 100 and 200nm/min depending on the substrate temperature. The crystallinity of as-prepared NiZn ferrite films became higher with increasing substrate temperature, but it could not reach a suitable value to produce magnetic properties suitable for practical applications. It was then necessary to anneal the films at higher temperatures above 600°C. Magnetic properties comparable with those of bulk NiZn ferrite and applicable to practical magnetic devices were obtained by annealing at 750°C. Furthermore, we attempted the preparation of well-crystallized NiZn ferrite thin films by adding hydrogen peroxide to the starting solutions.

磁気共鳴周波数が１ＧＨｚを越えるＮｉ‐Ｚｎフェライトめっき膜

Ni-Zn ferrite films 0.2-1.2 μm in thickness were prepared by spraying a reaction solution of FeCl2(+FeCl3)+NiCl2+ZnCl2 (pH = 6.95) and an oxidizing solution of NaNO2 + CH3COONH4 (+NH3) simultaneously onto spinning glass substrates at a substrate temperature of 90°C. Films with a thickness of 0.48 μm deposited by the conventional spin-spray method using only Fe2+ as iron ions exhibited a high permeability μ' of 42 and a high magnetic resonance frequency fr of 650 MHz. This was 5 times as high as the value for Ni-Zn ferrite bulk. Film plated by adding NH3 to an oxidizing solution and film deposited by using a mixture of Fe3+(10%) and Fe2+(90%) as iron ions exhibited higher fr values of 900 MHz and 1.2 GHz, respectively. Since not only the real part μ' but also the imaginary part μ'' had large values of about 30 at 1 GHz, the films prepared in this study will be applicable to rf inductors as well as wave absorbers for suppressing EMI in the quasi-microwave range exceeding 1 GHz.

Special Issue Ceramics Integration. Effect of Composition and Crystallinity of Epitaxial Ni-Zn Ferrite Films by Pulsed Laser Deposition on their Magnetic Properties.

Epitaxial (Ni-Zn)Fe2O4 thin film was prepared on Si(001) substrates using (MgO-Al2O3)/CeO2/YSZ triple buffer layer. In this work, to increase remanent magnetization (Mr) and decrease coercive field (Hc), for epitaxial (Ni-Zn)Fe2O4 thin film, the effect of substrate temperature, oxygen pressure and composition on the magnetic properties was examined. It was clarified that the remanent magnetization and coercive field were strongly influenced by temperature and oxygen pressure. In order to obtain high Mr and low Hc, it was thought that a substrate temperature of 800°C and oxygen pressure 1.3Pa were optimal conditions. As regarding the composition, Mr could be obtained to a maximum of 3.96×10-1Wb/m2 by changing the quantity of Zn and Fe(Ms=5.31×10-1Wb/m2, Hc=1.35×101kA/m).