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By utilizing a sharp magnetic needle made of a sintered Nd2Fe14B permanent magnet, we were able to produce a strong magnetic field of up to approximately 560 kA/m in a transmission electron microscope and succeeded in observing the magnetization reversal in a thin film of sintered Nd2Fe14B by in situ Lorentz microscopy. The increase in the magnetic field induced by the magnetic needle led to a pair of straight magnetic domain walls forming abruptly from the grain boundary. The successive nucleation in the neighboring grain started at the grain boundary adjacent to the magnetic domain wall formed first. Eventually, the magnetic domain walls in the neighboring grains connected and moved continuously and finally disappeared. [ABSTRACT FROM AUTHOR]

The magneto-optical (MO) imaging is one of the methods for visualizing the magnetization distribution corresponding to the leakage magnetic fields. In general, the MO imaging requires high-spatial resolution and high-contrast imaging. The spatial resolution of the MO imaging depends on the magnetic domain size. In this study, we used the polycrystalline garnet films with a domain size of about 50 nm for the high-resolution imaging. We also demonstrated MO imaging using the magnetophotonic crystal (MPC) with polycrystalline garnet films in order to improve the MO image contrast. The MO images of a carbon steel surface can be observed by means of the MPC. As a result, the high-spatial resolution and high-contrast MO image was obtained by MPC. [ABSTRACT FROM AUTHOR]

By the sterolithography technique and the ferrite plating, we fabricated three types of magnetic micromachines which coated Fe[SUB3]O[SUB4], Co[SUB0.39]Fe[SUB2.61]O[SUB4], and Co[SUB0.45]Fe[SUB2.55]O[SUB4], respectively. The stereolithography technique enables one to form the spiral-shape resinous templates and the ferrite plating enables one to coat the ferrites uniformly onto these templates from an aqueous solution. The total machine weight is light because a resin of the template body is almost the same density as water. We verified that the machines swim freely and wirelessly in water by applying a rotational magnetic field. As these machines coated with ferrites have the biocompatibility, there is the possibility of medical microrobots which swim in the human body for medical operations. [ABSTRACT FROM AUTHOR]

The effect of a magnetic field on the electrode potential of Fe, Co, Ni, and Cu in different electrolytes was investigated. The electrolytes used were iron(III) chloride (0.02-0.6 M/l), iron (III) nitrate (0.06 M/l), caustic soda (8 M/l), hydrochloric acid (0.1 M), and sulphuric acid (0.1 M). All measurements were made at room temperature in magnetic fields of up to 4 kOe. Results from experiments with nickel and cobalt ferromagnetic electrodes and different electrolytes showed no effect of magnetic field. On the contrary, magnetic field caused a proportional change in the potential of the ferromagnetic iron electrode in solutions of iron(III) chloride and nitrate, and caustic soda. A significant long-time drift of the potential was found in all electrolytes. The electrode magnetization change gives the change of the potential, which is not proportional to magnetization. [ABSTRACT FROM AUTHOR]

Abstract: We have developed a characterization method for two-dimensional imaging of critical current density in coated conductors (CCs) based on scanning Hall-probe microscopy (SHPM). The distributions of the magnetic field around a sample were measured for several different conditions of external magnetic fields, and then were converted to those of the sheet current density which flowed to shield the external magnetic field or to trap the penetrated magnetic field. As a result, it was found that the amplitude of the sheet current density corresponded to that of critical current density almost in all the area of the sample except for the region where current direction changed. This indicates that we could obtain an in-plane distribution of the critical current density with a spatial resolution of around 100μm in non-destructive manner by this method. We believe that this measurement will be a multifunctional and comprehensive characterization method for coated conductors. [Copyright &y& Elsevier]

A 128 by 128 magneto-optic spatial light modulator (MOSLM) with single magnetic domain pixels, which is driven by using only drive lines without external bias coil, is described. The array of pixels was formed with Bi substituted iron garnet film grown by liquid phase epitaxial (LPE) method. Since the magnetic switching field of the pixels was so large owing to their growth induced magnetic anisotropy, we reduced it by annealing. Straight copper lines, which have low electrical resistance and enable to apply a homogenous magnetic field to the pixel, were used as drive lines. Thesis improvements reduced an electric power 70% compared with conventional MOSLM and kept the pixels with a single magnetic domain after switching. Though the domain structure depended on the pulse width of current, the frame rate of 5 kHz was estimated by using optimized drive condition. [ABSTRACT FROM AUTHOR]

Nonlinear-optical manifestations of the Borrmann effect that are consequences of the spectral dependence of the spatial distributions of the electromagnetic field in a structure are observed in one-dimensional photonic crystals. The spectrum of the light self-focusing effect corresponding to the propagation-matrix calculations has been measured near the edge of the photonic gap. [ABSTRACT FROM AUTHOR]

Current transport properties in Y1Ba2Cu3O7δ (YBCO) coated conductors obtained by pulsed laser deposition process on a CeO2 capped Gd2Zr2O7-IBAD template have been studied by spatially resolved measurements. We utilized low temperature scanning laser microscopy along with laser induced Seebeck effect imaging and scanning SQUID microscopy that allow us to visualize 1) distributed flux flow dissipation, 2) current blocking obstacles and 3) local current flow, respectively. Combination of those measurements leads deep insights into current limiting mechanism in the coated conductor. Our results show that non-uniform current flow due to spatially distributed obstacles is responsible for the dissipation, whereas grain connectivity in each YBCO grains is not the limiting factor. Typical period of those obstacles is several tens μm to hundreds μm. Detailed correlation between local current flow and dissipation has been observed. Present methods have great potential as tools for basic understanding of current limiting mechanisms in the coated conductors. [ABSTRACT FROM AUTHOR]

Current transport properties in 200 A-200 m-class IBAD-YBCO coated conductor (CC) have been investigated over a wide range of temperature and magnetic flux density up to 26 T. YBCO CC fabricated by reel-to-reel pulsed laser deposition equipment with a multi-plume and multi-turn deposition system showed high critical current of 245 A in length of 212.6 m. Critical current density, Jc, in 5 T parallel to c-axis at 65 K and 4.2 K were 0.44 MA/cm2 and 5.5 MA/cm2, respectively. Moreover, even in very high magnetic flux density, the superior Jc property remains at lower temperature, e.g. Jc at 4.2 K in 26 T was 2 MA/cm2. We also showed analytical expressions of electric field vs. current density (E–J) characteristics based on a framework of percolation model and scaling law of the flux pinning properties. Using the expressions, E–J characteristics and Jc value at any conditions of temperature and magnetic flux density can be predicted quantitatively. [ABSTRACT FROM AUTHOR]

E–J characteristics in a YBCO coated conductor at low temperature and very high magnetic field up to 27 T have been estimated using experimental E–J characteristics below 12 T along with a scaling analysis based on the percolation model. 1 mm thick YBCO films was deposited on a biaxially aligned Y2O3/YSZ/Hastelloy substrate fabricated by the IBAD technique. The critical current Ic for the 1 cm wide tape was 85 A at 77 K in self-field. We measured E–J characteristics in perpendicular field up to 12 T using 100 μm wide and 1 mm long bridge patterned in the tape. Statistic Jc distribution and pinning properties were analyzed from the E–J characteristics. Using the pinning parameters determined by the scaling analysis, we can calculate the critical current properties as a function of temperature and magnetic field. E–J characteristics at low temperature and very high magnetic field up to 27 T were estimated analytically and compared with the experimental data. Estimated value of Jc and n-value, and their error analysis were also discussed. [Copyright &y& Elsevier]

Using limited data measurements, the electric field vs. current density (E-J) characteristics of practical Bi-2223/Ag tapes were predicted in a low-temperature and high-magnetic field. This method is based on findings shown in our papers, which describe E-J characteristics according to the percolation model, as a function of temperature, magnetic field and angle of the magnetic field. This method can also estimate critical current density and n-value, given any electric field criterion. [ABSTRACT FROM AUTHOR]

Extended E–J characteristics in a YBCO coated ion beam assisted deposition tape have been studied over a wide range of perpendicular magnetic field, B, and temperature, T. The statistical distribution of the critical current density, Jc, and the magnetic transition field have been analyzed within the frame work of the percolation model. It has been shown that the distribution of pinning strength in the coated tape is much sharper than that in an epitaxial thin film deposited on a SrTiO3 single crystalline substrate. This result suggests that effective pinning sites are introduced in the coated tape. Scaling behavior of the pinning force density will also be shown. The present analysis allows us to estimate the Jc value quantitatively at an arbitrary B, T and electric field criterion. [Copyright &y& Elsevier]

We have studied electrical properties of YBCO/Y/sub 0.7/Ca/sub 0.3/Ba/sub 2/Cu/sub 3/O/sub 7-x/ (Ca-YBCO)/YBCO trilayer junctions using c-axis oriented films. The Ca-YBCO films used here are the overdoped version of YBCO and show transition temperatures around 55 K. All of the junctions show RSJ-like current-voltage characteristics in a certain temperature range, though the range decreases with the Ca-YBCO interlayer thickness. For an applied magnetic field, the junctions show Fraunhofer pattern, indicating a Josephson coupling through the interlayers. The normal resistance of the junctions is proportional to the thickness of the interlayer, suggesting little interface resistance. The exponential dependence of the critical current on temperature and that on the interlayer thickness mean that the junctions behave as SNS junctions. These experimental results imply the proximity effect along c-axis in high temperature superconductors. [ABSTRACT FROM PUBLISHER]

Abstract: We have investigated current transport property in Gd1Ba2Cu3O7− δ coated conductor with artificial pinning centers in a wide range of temperature, magnetic field, B up to 27T, and field angle. Due to the additional c-axis correlated pins, critical current density, J c in B//c was enhanced and the improvement was observed in wide range of B. On the other hand, around B⊥c below 65K, the angular dependence of n-value showed a valley-like behavior, although the J c was increasing. In addition, the temperature dependence of the pinning force density defined as J c × B was not scaled on an expected master curve. These results indicate the pinning in B⊥c is governed by different mechanism below 65K and high magnetic field. [ABSTRACT FROM AUTHOR]

Presents information on a study that develops a theory for analyzing the flap motion of wings of small flying elements driven by an alternating magnetic field. Model and theory; Numerical parameters; Dynamic motion of wings; Conclusion.

The infrared reflectance spectra of α-ET2KHg(SCN)4 in applied magnetic fields up to 9.8 T are reported. A dip structure appears in the reflectance spectra around 1000 cm−1 below 10 K at B=0 T. This structure is associated with the density-wave formation in this salt. Under a magnetic field above 4 T, this dip structure disappears. A phase transition at a low magnetic field less than 4 T is suggested. [Copyright &y& Elsevier]

Abstract: Magnetic torque measurements of TPP[Fe(Pc)Br2]2 are reported. The torque curves for the magnetic field rotated within the ac plane exhibit a two-fold symmetry. The temperature dependences of the torque amplitudes divided by the square of the field strength (τφ =45/B 2) exhibit a drastic field dependence below 12K. This field dependence is attributable to the fluctuation in the spontaneous magnetization that appears below 4.5K. The torque curves for the field rotated within the ab plane exhibit four-fold symmetry. The curves are sinusoidal above 18K and exhibit saw-toothed shapes below ∼12K and complicated shapes below 8K. The complicated shapes suggest that both d-electrons and π-electrons form a magnetic order below 8K. [Copyright &y& Elsevier]

Abstract: We have visualized non-uniform current flow in RE123 coated conductors by using a scanning Hall-probe magnetic microscopy (SHPM). Newly developed SHPM system allows us to measure two-dimensional magnetic field distribution with high spatial resolution in micro-meter scale. Corresponding current density distribution can be obtained from the magnetic field image by solving inverted Biot–Savart’s law. One of the most important advantages of the present system is to visualize the current density distribution in practical high transport current and also in wide scanning area. For example, the system has current leads with large capacity up to 500A, and the operating distance can be 15cm by 15cm with a micro-meter step distance. Using the SHPM system, we have successfully visualized current density distributions in the coated conductor, and clarified different kinds of non-uniform current flow. Those insights are very useful to identify local defects as well as non-uniform tape quality. These results indicate that the SHPM system is a powerful diagnostic tool not only to observe spatial inhomogeneities of transport property but also to understand their reason in practical coated conductors. [Copyright &y& Elsevier]

So-called magnetic-superprism effect is studied consisting in an extremely large deviation of a light ray in a photonic crystal under the influence of an external magnetic field. It is demonstrated that the magnetic superprism effect is possible in one-dimensional magnetic photonic crystals. [ABSTRACT FROM AUTHOR]

Abstract: The necessary conditions for the observation of the Faraday effect in 2D magneto-photonic crystals are discussed. It is found. that the Faraday effect may be observed in the directions where any couple of the wave vectors of the harmonics consisting the Bloch waves of TE and TM solutions in zero magnetic field are identical. This direction corresponds neither to Faraday nor to Voigt geometry. [Copyright &y& Elsevier]

Abstract: Critical current (I c) of a Bi-2223 tape fabricated by controlled-overpressure (CT-OP) sintering method has been attained up to 200 A-class in recent years. However, current limiting factors have not been fully clarified yet. In this study, we have investigated local current distributions in a CT-OP Bi-2223 tape by using the scanning Hall probe magnetic microscopy. As a result, it has been found that large sheet current flows in the center of the sample. Even though the influence of self-field is taken into account, there is a clear difference of local I c across the width. The maximum sheet current value in the center of the tape is 400–450A/cm when we applied the bias current of 100A, which is equal to the I c at around 87K. This value is equivalent to 800–900A/cm at 77K taking into account the value of I c. Furthermore, such current distribution continues uniformly in length direction. From these results, we have concluded that improvement of current uniformity across the tape width is the effective way to enhance critical current for the present CT-OP Bi-2223 tape. Our results show the feasibility for 300 A-class I c at 77K. [ABSTRACT FROM AUTHOR]

Tunneling of microwave radiation through the surface Tamm state that is generated at the interface between two different periodic structures (photonic crystals) has been studied theoretically and experimentally. The possibility of controlling the transmission frequency of this system with the use of an external magnetic field has been predicted theoretically and confirmed experimentally. [ABSTRACT FROM AUTHOR]

Abstract: To improve J C properties in a magnetic field (J C–B) of YBa2Cu3O7− δ (YBCO) films by a TFA-MOD (trifluoroacetates metal organic deposition) method, we fabricated YBCO films with SnO2-doping as artificial pinning centers and investigated the superconducting properties and the crystalline structures. TFA-MOD is expected as a cost-effective method with a non-vacuum system to fabricate YBCO films with high superconducting properties. However, YBCO films have problems that J C decreases in a magnetic field (B). In this study, the TFA solutions with SnO2 for pinning centers were used as starting materials. In the transmission electron microscope image, existence of second phase particles with size of 20–30nm has been observed in the YBCO film. These nano-particles contained Sn-element and distributed randomly in the film. The J C/J C (self field) values of the SnO2-doped YBCO films were enhanced in all magnetic field angles. Therefore it is considered that 3D pinning centers of Sn-compounds were introduced into YBCO film. [Copyright &y& Elsevier]

Abstract: We study the Tamm states existing at the interface of a 1D magnetophotonic crystal made of magneto-optic material and a material with natural anisotropy. It is shown that in such a photonic crystal (PC) Yeh''s band gap may exist, which causes a special type of the Tamm state. As this state is due to magneto-optic properties, it is controllable by an external magnetic field. [Copyright &y& Elsevier]

The magnetorefractive effect in a one-dimensional magnetophotonic crystal, more specifically, a photonic crystal (SiO2/Ta2O5) containing a built-in defect in the form of a thin layer of the Co-(Al-O) magnetic nanocomposite, is studied in a computer simulation experiment. The structure of the unit cell of the photonic crystal in which most of the field energy is concentrated in cells nearest to the defect is determined. This makes it possible to increase the defect-mode Q factor and, owing to the multiple passage of light along the defect, to enhance the magnetorefractive effect by more than one order of magnitude as compared to a thin film on a substrate and by two orders of magnitude as compared to thick films. The reflectance of these structures in an applied magnetic field can be as high as 60%. [ABSTRACT FROM AUTHOR]

The magnetoresistance, magnetization, and microstructure of granular composites with the general formula (Fe[sub 40]Co[sub 40]B[sub 20])[sub x](Al[sub 2]O[sub 3])[sub 100 – ][sub x] were studied for contents of the amorphous metallic component both above and below the percolation threshold (x≈43). The low-temperature transverse magnetoresistance of the composites is negative at x = 41 and practically zero for x = 49. For metal contents below the percolation threshold (x = 31), a noticeable (7–8%) positive magnetoresistance, reached in magnetic fields of about 17 kOe, was observed. Possible mechanisms of the generation of inverse (positive) magnetoresistance are discussed. © 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Abstract: We have demonstrated a magneto-optical spatial light modulator in which functionality is realized by (i) heating up to Curie temperature (T c) magneto-optical elements (pixels) with a semiconductor laser and (ii) application of a switching magnetic field. The pixels were made of films of amorphous rare earth–transition metal compounds (TbFe films with T c=403K and DyFe films with T c=343K) having good magneto-optical responses for wavelengths from the visible spectral range. We have found that the magnetization direction of pixels can be modulated with a laser radiation density of 5mJ/cm2 and in a switching magnetic field of 15Oe. [Copyright &y& Elsevier]

Abstract: The magnetoelastic effect was studied in amorphous ribbons with different compositions. The elastic waves were excited as a result of magnetostriction by the weak AC magnetic field at frequencies till 100kHz. The AC magnetic field was applied locally. A piezoelectric sensor was used to control the amplitude of the standing acoustic vibrations, and a pick-up coil measured the magnetization change. The output signal was measured by the selective nanovoltmeter. The standing waves amplitude and phase distribution depended on external DC magnetic field and stresses in amorphous ribbon. [Copyright &y& Elsevier]