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Volume 61, Issue S1
Displaying 51-86 of 86 articles from this issue
Soft Magnetic Materials
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C. Beatrice, O. Bottauscio, F. Fiorillo2014 Volume 61 Issue S1 Pages S208-S210
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSWe present a general approach to magnetic losses in Mn-Zn ferrites and apply it to broadband (DC –1 GHz) measurements performed on different types of sintered ring samples. The separate contributions of rotations and domain wall displacements to the magnetization process and the associated dissipation mechanisms are recognized and treated under the concept of loss decomposition, where hysteresis, excess, and classical components are separately identified. By investigating the role of sample size, the eddy current losses are singled out and calculated by means of a variational multiscale approach, taking into account the heterogeneous structure of the material. In sufficiently small samples, spin damping becomes the sole relevant dissipation channel. When involving the spin precession inside the moving domain walls, it gives rise to the hysteresis and excess loss components. The frequency dispersion of the domain wall susceptibility, experimentally separated from the rotational susceptibility, is consistent with a relaxation process, with no resonances involved. Beyond a few MHz, only rotations inside the domains survive and the associated losses are described via the Landau–Lifshitz–Gilbert equation for spin dynamics, with distributed effective anisotropy fields.View full abstractDownload PDF (388K) -
R. Lebourgeois2014 Volume 61 Issue S1 Pages S211-S213
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSThe present trend in power electronics is the increase of power density and the reduction of the size and cost of devices. It is now mandatory to find new solutions to reach high integration levels without decreasing the efficiency and by considering thermal issues. Recently, a new family of low-loss ferrites emerged for high frequency applications (>1 MHz). These ferrites are nickel-zinc-copper-cobalt spinel ferrites and can be favorably used in very compact high frequency SMPS (Switching Mode Power Supplies). This paper presents their magnetic properties in comparison with the state of the art of power ferrites.View full abstractDownload PDF (469K) -
J. Töpfer, J. Hesse, S. Bierlich, S. Barth, B. Capraro, T. Rabe, H. Na ...2014 Volume 61 Issue S1 Pages S214-S217
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSWe have studied the integration of Ni-Cu-Zn ferrite spinels as well as substituted hexagonal Co2Y-and M-type ferrites into LTCC (Low Temperature Ceramic Co-firing) modules. The cofiring behavior and the magnetic properties of these materials were investigated and evaluated for multilayer applications. Ni-Cu-Zn ferrites exhibit permeabilities of μ=300–500 for operating frequencies in the MHz range. Cu-substituted Y-type ferrites Ba2Co2-x-yZnxCuyFe12O22 in combination with sintering additives display sufficient shrinkage and densification at 900°C. A permeability of μ=10 is observed; however, substituted Co2Y-type ferrites do not exhibit long-term stability at 900°C. Co/Ti-substituted M-type ferrites BaFe12-2yCoyTiyO19 (y=1.2) with planar magneto-crystalline anisotropy exhibit excellent soft magnetic behavior. Using sintering additives, complete densification is reached at 900°C and a permeability of μ=15 and a resonance frequency of larger than 1 GHz are observed. Integration of ferrite multilayer inductor components into LTCC modules using free and constrained cofiring technologies is demonstrated.View full abstractDownload PDF (358K) -
A. M. Elshahawy, M. H. Mahmoud, S. A. Makhlouf2014 Volume 61 Issue S1 Pages S218-S220
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSNi1-xCuxFe2O4 nanoparticles were successfully synthesized by a microwave-induced combustion process using urea as fuel. The XRD study confirmed the formation of a single-phase of cubic spinel Ni-Cu ferrite at low copper content. However, CuO is identified as a minor phase for x>0.15. Room temperature magnetization results showed that the magnetization increases and the coercivity decreases with increasing copper content.View full abstractDownload PDF (334K) -
M. Y. Lu2014 Volume 61 Issue S1 Pages S221-S223
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSA MnZn ferrite material with larger electrical resistance, which can be used in high frequency region exceeding 1 MHz, is investigated. The MnZn ferrite material with iron defect in the composition comprises the following basic components: 48.6 mol% Fe2O3, 24.2 mol% ZnO, 25.2 mol% MnO, and the remainder being TiO2 and SnO2. By the addition of TiO2 and SnO2, even if the ferrite material is sintered in air, electrical resistance of 103 times that of the conventional MnZn ferrite can be obtained, and high initial permeability of 350 to 500 as estimated can be secured even at high frequency of 5 MHz. It is well known that Sn and Ti receive electrons from Fe3+ to form Fe2+. Since many Sn4+ and Ti4+ having the stable number of valency are present, exchange of electrons between Fe3+ and Fe2+ are substantially inhibited, and as a result, electrical resistance far larger than the conventional one (about 103 times) can be obtained. This kind of ferrite material is suitable for switching power supply, a rotary transformer, choke coils, electronic parts such as for various kind of inductance elements and impedance elements for countermeasure against EMI, or for electromagnetic absorbers.View full abstractDownload PDF (268K) -
K. Mori, K. Yasuhara, I. Nakahata, K. Nishikawa2014 Volume 61 Issue S1 Pages S224-S226
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSHigh temperature stability on core loss of Co-doped MnZn ferrite was investigated. It is confirmed that addition of Ti to Co-doped MnZn ferrite increased high temperature stability of core loss remarkably. By addition of Ti, degradation degree of core loss in a temperature range from 25°C to 150°C is less than 5% during high temperature storage test at 150°C for 2000 hours. According to the relationship between cation vacancy and degradation degree, the Ti-doped materials show low degradation degree even in present of much cation vacancy. The activation energy of cation diffusion was estimated from the degradation degree of core loss, the activation energy of Ti-doped material increased by approximately 10%, compared with only Co-doped material. As a result, an excellent ferrite material with both low loss and high temperature stability of core loss suitable for automobile was developed.View full abstractDownload PDF (350K) -
E. Brun, R. Lebourgeois, E. Laboure2014 Volume 61 Issue S1 Pages S227-S230
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSIn Switching Mode Power Supplies, ferrites with low permeability and low losses are required to make inductors. (NixZnyCuz)1-εCoεFe2O4 ferrites are good candidates to meet this objective. Their permeability can be controlled by adjusting the Ni/Zn ratio and the Co content. Cobalt induced anisotropy lowers the core losses and leads to a more resonant behavior of the complex permeability spectra [1]. Cobalt substitution also modifies the variation of the magnetocrystalline anisotropy versus temperature, leading to a minimum loss at the compensation temperature, depending on the cobalt content and the Ni/Zn ratio [2]. By controlling those parameters, ferrites low core losses at high frequency and permeability lower than 100 have been obtained. Core losses have been measured between 1 and 2 MHz, for induction level up to 25 mT, and the contribution of the winding to those losses has been evaluated, from less than 10% for the highest permeability values to around 20%. Core losses lower than the state of the art were obtained, for materials with a permeability range from 40 to 135.View full abstractDownload PDF (369K) -
K. Shimba, Y. Hoshi, M. Matsuura, N. Tezuka, S. Sugimoto2014 Volume 61 Issue S1 Pages S231-S233
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSIn this paper, amorphous Fe-B (AFB) submicrometer particles were coated with ferrite by the ferrite plating method. The AFB/ferrite composite particles (AFC particles) showed higher resistivity than AFB particles. The polymer composites of AFC particles also showed higher resistivity than those of AFB particles, which lead to suppression of electric conduction and eddy current loss in highly-filled polymer composites. Therefore, AFC particles using ferrite plating method were effective for the increase in volume fraction of metallic particles with a size of submicrometer, and for suppressing eddy current loss.View full abstractDownload PDF (673K) -
S. Gotoh, K. Ikeda, T. Otake, Y. Fukuda2014 Volume 61 Issue S1 Pages S234-S237
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSA new MnZn ferrite with low core loss, Pcv and high saturation flux density, Bs above 100°C have been developed as a material suitable for transformer or inductor cores, which operate in the high temperature range from 130 to 150°C. The material with the Bs of 400 mT at 140 ºC and the Pcv of 286 kW/m3 at 140°C, 100 kHz and 200 mT have been obtained, and it is most suitable for onboard power supplies etc. The magnetic properties of the core were realized by choosing the desired compositions and optimizing the sintering conditions. In order to decrease the Pcv and to increase the Bs, it is necessary to select a composition in which magnetic anisotropy and magnetostriction are zero in the ternary system of MnO-ZnO-Fe2O3 and to add NiO to the main composition. Furthermore, by controlling the temperature and the atmosphere precisely in sintering, the adequate uniform grains and the grain boundaries, in which trace additives are precipitated, are realized in the core which is as free as possible from defects, pores, impurities, etc. within grains at the same time, and thereby the low loss and the high saturation flux density were improved in the high temperature range above 100°C.View full abstractDownload PDF (248K) -
H. Oshima, Y. Uehara, K. Shimizu, K. Inagaki, A. Furuya, J. Fujisaki, ...2014 Volume 61 Issue S1 Pages S238-S241
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSNi-Zn ferrite cores under dc bias are experimentally characterized, and the results are compared with those of simulation. Hysteretic behavior of a toroidal core at high frequencies and the effect of dc bias are well reproduced by simulation with a hysteresis model that we have developed recently, a grain magnetics (GM) model. The inductance and core loss of a wirewound inductor under high-frequency excitation with dc bias are also measured. We show that the finite element analysis with the hysteresis model provides simulation results close to the experimental data of the inductor.View full abstractDownload PDF (1562K) -
K. Shiroki, K. Kawano, H. Matsuura, H. Kishi2014 Volume 61 Issue S1 Pages S242-S244
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSNew type of metal composite material has been developed for the power inductor application. Careful surface treatments of the Fe-based metal powder establish the highly crystallized nano-scale oxide layer on the power surface, and this oxide provides the enough strength and the electronically insulation even without the resin between powders.View full abstractDownload PDF (475K) -
M. Suzuki, K. Kawano, T. Matsuo, T. Mifune, Y. Uehara, A. Furuya, H. I ...2014 Volume 61 Issue S1 Pages S245-S247
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSMagnetic properties of mono-domain and multi-domain NiZn ferrites under dc magnetic flux densities were investigated with regard to actual performance in power circuits. Bias properties were measured along the initial magnetization curve. The magnetizing process in the multi-domain sample is mainly dominated by domain-wall motion even in the low ac magnetic flux density region. In contrast, in the mono-domain sample, magnetization is reversible and core loss is low regardless of the dc magnetic flux density because the spin rotation dominates if ac flux density is below 20 mT.View full abstractDownload PDF (330K) -
D. Q. Guo, K. C. Chan2014 Volume 61 Issue S1 Pages S248-S251
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSMagnetic refrigeration, based on the magnetocaloric effect (MCE), has already been applied in low temperature applications. There are, however, limitations in room temperature applications, and many researchers are now working on this issue. The refrigeration capacity (RC), which reflects the MCE, of amorphous materials has been proven to be generally larger than that of crystals. Among various amorphous magnetic materials, although the Fe-based materials have general MCEs, their advantages of high Curie temperature (TC) and low cost have attracted considerable attention and investigation. In order to enhance the MCE, the influence of Co addition on a Fe-based amorphous material was investigated in this study. Fe76-xCoxSi5Cr4Zr5B10 (x=0, 2, 4, 6) ribbons were fabricated and their MCE was studied under a maximum field of 1193.7 kA/m. The results show that Fe74Co2Si5Cr4Zr5B10 ribbon demonstrated good performance when both refrigeration capacity and Curie temperature are taken into consideration (TC=295K, RC=56.1 J/kg). Since the Curie temperature of this alloy is close to room temperature. It is envisaged that with further improvement of its RC, this material is promising for magnetic refrigeration at room temperature.View full abstractDownload PDF (344K)
Hard Magnetic Materials
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S. Ito, T. Nagatake, Y. Yamaguchi, K. Fujimoto2014 Volume 61 Issue S1 Pages S255-S257
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSThe powder compact of Ba ferrite was directly sintered by hot isostatic press (HIP). Using HIP, grain growth was successfully controlled and densification was achieved at low temperature. The Ba ferrite powder prepared by coprecipitation was densified to 99.6% without grain growth by sintering at 1000°C for 1 h under 200 MPa. The average grain size of the Ba ferrite obtained was 0.2 µm, which was comparable to the particle size of starting powder. This Ba ferrite revealed 10.3 kJ/m3 in (BH)max. This (BH)max was increased to 14.1 kJ/m3 by annealing the Ba ferrite at 1000°C for 1 h under atmospheric pressure. The improvement of (BH)max is due to the relaxation of the internal stress induced by HIP sintering.View full abstractDownload PDF (426K) -
G. Obara, H. Hamada, K. Saikachi2014 Volume 61 Issue S1 Pages S258-S261
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSThe effects of CaO and SiO2 inter-additives on magnetic and physical properties of Ca-La-Co system ferrite sintered magnets were discussed. The results show that the maximum magnetization and remanence of the sintered magnets decrease with an increase in the ratio of SiO2 to CaO inter-additives, because non-magnetic materials α-Fe2O3 are formed with an increase in the ratio. On the other hand, the coercivity HcJ of Ca-La-Co system sintered magnets increase with an increase in the SiO2 additives, because the average particle size of sintered magnets becomes smaller. Whereas, HcJ of Ca-La-Co system sintered magnets decrease with an increase in the CaO inter-addition because the crystal growth of the sintered magnets occurred due to CaO inter-additive. Optimum magnetic properties and conditions in this experiment were as follows; inter-additives: 0.3 wt.% SiO2 and 0.5 wt.% CaO, sintering temperature: 1200°C, Br=0.429 [T], HcJ=278 [kA/m], (BH)max=34.5 [kJ/m3].View full abstractDownload PDF (284K) -
J. Kato, D. Matsubayashi, K. Yamauchi, M. Inagaki, K. Ono2014 Volume 61 Issue S1 Pages S262-S265
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSBarium ferrite doped with Bi and Si oxide was sintered densely at a low temperature of approximately 900°C, suppressing grain growth. This ferrite magnet had a two-phase structure comprising a barium ferrite phase and an amorphous bismuth silicate phase. We investigated the relationship between the magnetic properties and SiO2 content and found that the coercive force increased in proportion to the SiO2 content. It was suggested that the coercive force increased because each grain was magnetically shielded by a grain boundary phase.View full abstractDownload PDF (946K) -
N. Nagasawa, S. Ikeda, A. Shimoda, T. Waki, Y. Tabata, H. Nakamura, H. ...2014 Volume 61 Issue S1 Pages S266-S269
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSWe have measured the 57Fe Mössbauer spectra of Sr1-xLaxFe12-xNixO19 (x=0, 0.1 and 0.2) at room temperature using the powder and the single crystalline samples. All observed spectra were well fitted using the five subspectra, which correspond to the five nonequivalent Fe sites. In Sr1-xLaxFe12-xNixO19 (x=0.1 and 0.2), the substitutions of Ni2+ ions for Fe3+ ions are required by the electric charge balance. For SrFe12O19, the relative absorption intensities in the spectrum observed using the single crystalline sample are much different from those observed using the powder one. This result shows large anisotropies of the recoilless fractions at the Fe sites. The refined hyperfine interaction parameters of the 4f1, 2a, and 2b sites decrease linearly with increasing x. The substitution of a Ni2+ ion for a Fe3+ ion changes hyperfine interaction parameters by the perturbation of the Fe-O-Ni hybridizations. Accordingly, the Fe ions in the vicinity of the 4f1, 2a, and 2b sites are replaced by the Ni2+ ions.View full abstractDownload PDF (387K)
Microwave Materials & Technologies
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V. G. Harris, Y. Chen, Z. Chen, A. L. Geiler2014 Volume 61 Issue S1 Pages S273-S279
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSThe role of magnetic anisotropy and crystallographic texture in determining rf properties of ferrites, and their performance characteristics when integrated within high frequency devices, is explored. Both thin film epitaxial and bulk polycrystalline texture are discussed defining viable paths to realizing crystallographic texture required for device integration. Of the broad classes of ferrite, we focus much of our attention on the versatile hexaferrite materials systems.View full abstractDownload PDF (603K) -
M. Yoshikiyo, A. Namai, S. Ohkoshi2014 Volume 61 Issue S1 Pages S280-S284
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSThis review article describes the large coercive field and high frequency millimeter wave absorption of ε-Fe2O3. In 2004, we obtained pure ε-Fe2O3 phase by a particular chemical synthesis method for nanosize particles, a combination method of reverse-micelle and sol-gel techniques. This ε-Fe2O3 exhibits a huge coercive field of 20 kOe at room temperature. In addition, its physical properties can be widely controlled by substituting the iron cations with other metal cations. In this paper, the synthesis, crystal structure, magnetic properties, and especially, the millimeter wave absorption properties of ε-Fe2O3 and metal substituted ε-Fe2O3, ε-MxFe2–xO3 (M=Al and Ga) are presented. ε-Fe2O3 and ε-MxFe2–xO3 based magnets have the possibility as millimeter wave absorbers for the future high-speed wireless communications.View full abstractDownload PDF (883K) -
T. Hasegawa, R. Nakajima, S. Ichiguchi, T. Wada, M. Koshino, T. Okada2014 Volume 61 Issue S1 Pages S285-S287
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSWe studied cellular phone isolator of gyrator type operating in weak magnetic field below ferromagnetic resonance and derived design equation in order to reduce the insertion loss. Using this design equation and the optimized coupling factor, a small sized Core-Isolator (0.5×1.6×0.4 mm3) for cellular phone terminals has been realized, and the insertion loss of 0.5 dB max and the isolation of 19.8 dB min. have been obtained successfully at 2.57 GHz to 2.62 GHz.View full abstractDownload PDF (307K) -
G. Cochet, A. G. Schuchinsky, P. Queffelec, V. Laur, R. Cahill2014 Volume 61 Issue S1 Pages S288-S292
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSThe properties of metasurfaces composed of doubly periodic arrays of interwoven quadrifilar spiral conductors on magnetized ferrite substrates have been investigated with the aid of the full-wave electromagnetic simulator. The effects of incident wave polarization and ferrite magnetization on the scattering characteristics have been analysed at both normal and in-plane dc magnetic bias. The features of the fundamental topological resonances in the interwoven spiral arrays on ferrite substrates are illustrated by the simulation results and the effects of ferrite gyrotropy and dispersion on the array resonance response and fractional bandwidth are discussed.View full abstractDownload PDF (353K) -
A. Harada, T. Ishikura, M. Muramoto, K. Yasuhara, S. Itoh2014 Volume 61 Issue S1 Pages S293-S295
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSEffect of Fe3+ substitution and grain size on magnetic properties in GHz range of M-type hexaferrites BaFe12-x(Ti0.5Mn0.5)xO19 (0≤x≤5) was investigated. Measured complex permeability spectra were well fitted by a model consisting of two types of magnetic susceptibilities corresponding to gyromagnetic spin rotation and domain wall motion. The model fitting shows μ′ in the GHz range is increased when a contribution of the gyromagnetic spin rotation is enhanced. Furthermore, from grain size distribution, it is shown that magnetic loss in the GHz range could be reduced when the average grain size increases and coefficient of variation (CV) decreases. This indicates contribution of a domain wall motion to the magnetic loss is reduced because the domain wall resonance peak shifts to lower frequency and becomes narrower. In our study, it is demonstrated that enhancement of μ′ with low magnetic loss is possible in the GHz region between two resonance peaks of a lower domain wall peak and a higher gyromagnetic spin rotation peak in M-type hexaferrites.View full abstractDownload PDF (529K) -
E. Eleftheriou, V. Tsakaloudi, G. Kogias, M. Zagorowska, V. Zaspalis2014 Volume 61 Issue S1 Pages S296-S298
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSNon reciprocal components (i.e. circulators, phase shifters etc.) involved in satellite radar telecommunications at frequencies around 95 GHz are required to have particularly low losses for optimum performance. In this article the development of W, Y and M type hexagonal ferrite materials is described together with their magnetic performance away from ferromagnetic resonance, that is at low frequencies (1 GHz) as well as at the W-band (around 95 GHz). From the results, it appears that the M-structure is the most suitable material for the manufacturing of components for narrowband applications (IL <−1 dB at 94.5 GHz). The nature of the damping mechanism in the off-resonance cases is also discussed.View full abstractDownload PDF (332K) -
K. Kondo, S. Yoshida, Y. Toyota2014 Volume 61 Issue S1 Pages S299-S302
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSTo confirm the feasibility of suppressing electromagnetic interference (EMI) in the inner layers of multilayered printed wiring boards (PWBs) and sustaining power integrity characteristics, influence of inserting a ferrite-plated thin film between the power and ground planes on the transmission characteristics were evaluated using four types of test boards with the following two conditions: one is the solid test board with a plane copper foil or the EBG (Electromagnetic bandgap) test boards with a one-dimensional lattice-shaped EBG structure consisting of large and small squares 15 mm×15 mm and 1.5 mm×1.5 mm in size; the other is whether the 3 or 6 µm-thick ferrite film was deposited or not. The multiple peaks of the transmission coefficient S21 due to parallel plate resonances were observed in the solid test board without ferrite film but the peaks were suppressed over the wide frequency range up to 6 GHz by applying the ferrite film. The EBG test board with the ferrite film provided not only wideband attenuation owing to the ferrite film but also large attenuation in the EBG stopband. The multiple peaks of in the driving point impedance Z11 due to the parallel plate resonances were also successfully suppressed by applying the ferrite film exhibiting favorable power integrity characteristics.View full abstractDownload PDF (402K) -
S. Takeda, S. Motomura, T. Hotchi, H. Suzuki2014 Volume 61 Issue S1 Pages S303-S307
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSThe wideband measurement system of permeability for magnetic thin slab was proposed for up to 10 GHz, using the all shielded shorted microstrip lines. In order to analyze this configuration, the reference plane was set on the other end of specimen where the LC parallel resonant circuit was assumed. The permeability was derived from the measurement of S11 by VNA (Vector Network Analyzer) comparing between with strong static magnetic field parallel to rf magnetic field and without it. The shorted microstrip line was calibrated by the standard sample of rectangular shape NSS (Noise Suppression Sheet) comparing with the results of toroidal core measured by the shorted coaxial line.View full abstractDownload PDF (371K)
Thin Films
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H. Sakuma, Y. Shidara, Y. Kagi, R. Suzuki, K. Ishii2014 Volume 61 Issue S1 Pages S311-S313
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSIn our previous study, we found that magnetite is epitaxially grown on GaAs substrate pre-annealed in air. While the formation of an oxidized layer is confirmed on GaAs by electron microscopy, the composition and crystal structure was unknown. In this study, the oxidized layer is revealed to be β-Ga2O3, of which (100) plane is parallel to the substrate plane by x-ray and electron diffractions. It disappears during the sputter deposition of magnetite on it, and a clear Fe3O4/GaAs interface is formed. The epitaxial relationship of the Fe3O4/GaAs heterostructure is cube-on-cube in contrast to that fabricated by a conventional method.View full abstractDownload PDF (1146K) -
H. Yoshiga, K. Kamishima, N. Hiratsuka, K. Kakizaki2014 Volume 61 Issue S1 Pages S314-S317
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSLa-Co substituted BaM (La-CoBaM) thin films have been prepared by a sol-gel technique involving a spin coating of metal-organic compounds. We report the effects of Pt under-layer on the c-axis orientation of La-CoBaM films and their magnetic properties. On the Pt under-layer with the thickness of 120 nm whose ‹111› axis oriented perpendicular to substrate surface, the La-CoBaM films with the thickness ranging from 20 to 95 nm were coated at room temperature. These coated films were annealed at 900°C for 5 h. in air. The Hc⊥/Hc// value for the La-CoBaM films with the thickness of 20 nm was 3.9 that was the largest of all samples. The c-axis of magnetoplumbite phase was oriented perpendicular to the film surface, that was caused by the effect of the (111) oriented Pt under-layer.View full abstractDownload PDF (786K) -
Y.-I. Kim, Y.-H. Lee, K.-B. Kim, K.-H. Kim2014 Volume 61 Issue S1 Pages S318-S320
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSTwo pyramidal indenters, one nearly sharp and one worn, were used to investigate contact deformation and nanohardness of a gold film. By superposing area functions of the two indenters on the Berkovich pyramidal relationship, the bluntness distances, hbs of the indenters could be estimated; hb values were 8.19 and 40.08 nm for the NEW and OLD indenters, respectively. Nanoindentations on a gold film produced different data from the two indenters; the peak indentation loads of the OLD indenter were higher than those of the NEW one at corresponding indentation depths because the blunt or OLD indenter caused more severe contact deformations at higher loads. Nanohardness trend analyzed from raw nanoindentation curves of the NEW indenter seemed to be lower than that of the OLD indenter. In order to compensate the apex blunting, the raw nanoindentation curves of each indenter shifted along the indentation depth axis by the amount of the bluntness distance. Conclusively, nearly overlapping nanohardness trends could be obtained regardless of the indenter from the shifted nanoindentation curves. The nanohardness values recalculated were consistent within 0.45% at deep indentation regime where all indenters acted as the perfect Berkovich pyramid.View full abstractDownload PDF (411K) -
J. Yan, M. Gomi, T. Hattori, J. Qiao, T. Yokota2014 Volume 61 Issue S1 Pages S321-S323
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSBiFe1-xAlxO3 thin films with rhombohedral (R3c), monoclinic (Cm) and tetragonal (T)-like symmetry were obtained by the chemical solution deposition (CSD) and rapid thermal annealing (RTA). The T-like phase is formed under high temperature and high Al concentration. While the Cm phase is stable in the region of low temperature and high Al concentration. The phase transition is suggested to be arisen from strain induced in the film formation.View full abstractDownload PDF (523K) -
J. S. Hong, T. Watanabe, H. Wagata, K. Katsumata, K. Okada, N. Matsush ...2014 Volume 61 Issue S1 Pages S324-S326
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSHeterostructured α-Fe2O3/ZnO films were fabricated by using spin-spray method and properties of each layer and heterostructured α-Fe2O3/ZnO film were investigated. First, as-deposited ZnO layer on glass substrate exhibited high transmittance of above 80% in visible range and a low resistivity of 1.8×10−2 Ω·cm. The formation of α-Fe2O3 layer on glass substrate was confirmed by XRD. This α-Fe2O3 layer was successively deposited on ZnO layer and it was confirmed that heterostructured α-Fe2O3/ZnO double layered films could be fabricated by aqueous solution process.View full abstractDownload PDF (483K) -
N. Okamura, T. Fujii, J. Takada, M. Nakanishi, J. Kano, N. Ikeda2014 Volume 61 Issue S1 Pages S327-S329
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSRare-earth iron oxides (RFe2O4) have attracting attention as new electronic device materials because of their abundant functionalities such as ferroelectricity, ferrimagnetism, and high infrared absorption. These properties are strongly related to the mixed iron valance states between Fe2+ and Fe3+. We tried to prepare RFe2O4 films by using soft chemical method. The films were prepared by spin-coating of viscous aqueous solutions of Yb(CH3COO)3 and Fe(NO3)3 with citric acid. The molar ratio between Yb : Fe was 1 : 2 and the citric acid : metal ratio was set to 3.75 : 1. After the coating, the films dried at 100°C for 10 min in air were, heat-treated at 900°C for 0.2 h in H2/CO2 gases to control oxygen partial pressure, and quenched. The obtained films were characterized by using XRD, SEM, EDS, Mössbauer, and optical-absorption spectra. The XRD pattern clearly indicated the well-crystallized and nearly monophasic YbFe2O4 formed on the substrates above 900°C to control the oxygen partial pressure. Equal amount of Fe2+ and Fe3+ ions was present in the films. The films showed small band-gap and large optical absorbance in infrared region.View full abstractDownload PDF (415K) -
T. Matsumoto, N. Suzuki, S. Kanamaru, H. Hashimoto, M. Nakanishi, T. F ...2014 Volume 61 Issue S1 Pages S330-S332
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSIlmenite-hematite solid solution (Fe2-xTixO3) is known to have unique magnetic and electric properties. It is one of the candidates for novel magnetic semiconductors with the high Curie temperature (Tc). The carrier type of Fe2-xTixO3 is controllable by changing the Ti content x. In order to fabricate the semiconductor devices, epitaxial thin films having good crystallinity with precise control of their carrier type are required. We have already succeeded in preparing well-crystallized epitaxial Fe2-xTixO3 (x=0.7) films on α-Al2O3 (110) single-crystalline substrates by reactive helicon plasma-sputtering technique. The films are expected to have n-type conduction, while the films having the higher Ti content could be p-type conduction. In this research, we tried to prepare (110)-oriented solid solution films over a wide composition range.View full abstractDownload PDF (534K)
Electro-Magnetic Devices, Magneto-Optics, & Recordings
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I. Shibasaki2014 Volume 61 Issue S1 Pages S335-S339
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSThe integration of InSb thin film with a ferrite substrate and ferrite chip to form high-sensitivity thin-film Hall elements for use as a magnetic sensor inside a very small plastic package led to a vast array of commercial applications. Hall elements have a magnetic field sensitivity about 3–6 times that obtained using InSb thin film alone. They have been used to develop many kinds of very small DC brushless, or Hall, motors and have been applied to many key devices such as contactless sensors, switches, current sensors, and many kinds of home-use electrical systems and car sensors. More than 24 billion Hall elements with the ferrite sandwich structure have been fabricated and applied over the last 30 years.View full abstractDownload PDF (738K) -
H. Fuketa, Y. Shinozuka, K. Ishida, M. Takamiya, T. Fujii, H. Shimizu, ...2014 Volume 61 Issue S1 Pages S340-S342
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSIn this paper, an inductor on interposer with a ferrite film is investigated for power supply circuits in order to improve the efficiency of the power supply circuits by introducing a high permeability material to the inductor. A DC-DC buck converter is used as a power supply circuit in this work. The dependence of the inductance on the location of ferrite film is discussed with field electromagnetic simulations. Simulation results indicate that the ferrite film should be located on both upper and lower sides of the inductor and between metals. By using the inductor with the 10 µm-thick ferrite film, the efficiency of buck converter is improved by 13% when the efficiency of buck converter with the air core inductor is 60%.View full abstractDownload PDF (396K) -
Y. Shoji, M. Yanaga, T. Kashima, T. Suzuki, S. Nakagawa, T. Mizumoto2014 Volume 61 Issue S1 Pages S343-S345
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSA magneto-optical isolator is indispensable for optical fiber communication to protect active devices from unwanted reflections. A ferrite garnet such as yttrium iron garnet (YIG) is typically used because of its transparency and relatively large magneto-optic effect for near-infrared light (~0.8 eV). However, a YIG film must be epitaxially grown on a garnet substrate, which makes it difficult to integrate optical isolators with other photonic devices. In a literature, a cobalt ferrite has specific peak of magneto-optic effect at the infrared wavelength.We then propose and design an ultra-compact magneto-optical isolator with cobalt ferrite on silicon photonic circuits. The isolator is based on a Mach-Zehnder interferometer of silicon optical waveguide fabricated on a silicon-on-insulator wafer. A cobalt ferrite film is partially deposited on the interferometer arms. In our design, the length of the nonreciprocal phase shifter is about 35μm which is on tenth of the case with Ce:YIG. We deposited cobalt ferrite films on buffer layer by a sputtering deposition. A (400)-oriented CoFe2O4 film was fabricated on FeO/Fe buffer layer to achieve low material loss.View full abstractDownload PDF (357K) -
N. Honda, K. Yamakawa2014 Volume 61 Issue S1 Pages S346-S349
Published: March 31, 2014
Released on J-STAGE: May 28, 2014
JOURNAL OPEN ACCESSProposed exchange coupled composite (ECC) magnetic dot structure consisting of three layers was studied by simulation for practical design of the magnetic recording media. Induced perpendicular anisotropy due to the layer stacking as well as the shape anisotropy of the soft layer for a square prism ECC dot was estimated. The ECC dots with the modified perpendicular anisotropy fields for the layers exhibited a minimum switching field and a flat applied field angle dependence of the switching field near perpendicular direction as expected. This would contribute to decrease write track width or increase cross track shift margin. It is concluded that consideration of the shape and layer stacking perpendicular anisotropy is indispensable for designing practical ECC dots.View full abstractDownload PDF (413K)