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Abstract: The trial for quantitative evaluation of inter-granular coupling in stacked perpendicular recording media is reported. The evaluation is realized by analyzing magnetic domain in relation with microstructure of the cap layer initial growth layer. When the thickness of cap layer is increased, the change of magnetic domain from single magnetic domain to maze magnetic domain can be observed. The critical thickness of the cap layer where the change happened was around 5.1nm. According to this analysis, when granular layer and cap layer of stacked media are assumed to be single layer, inter-granular coupling with amount of around 2.9erg/cm2 was obtained which agrees with the simulation result qualitatively. [Copyright &y& Elsevier]

By pulsed-neutron diffraction experiments on a DyRu2Si2 single crystal in an external magnetic field as well as in zero field we have confirmed peculiar one- and two-dimensional spin orderings in zero field, in which two paramagnetic (2 0 0)/(1 0 0) planes and two frustrated paramagnetic Dy ions are contained in the magnetic unit cells of 9a×a×c and 9a×9a×c, respectively, and made clear magnetic structures of the field-induced-metamagnetic phases. The zero field two-dimensional magnetic structure changes to one-dimensional without any paramagnetic Dy ion at H=0.5 T, similar to the high-temperature structure. At H=1.2 T, the spin arrangement becomes again two-dimensional without any paramagnetic Dy ion, then it changes at H=1.9 T to another -two-dimensional arrangement with more ferromagnetic components, and finally undergoes a fully-induced-ferromagnetic structure. [Copyright &y& Elsevier]

Abstract: To perform the first-principles calculation of a non-uniform electron system with both localized and delocalized electrons, we have developed a calculational method based on a newly developed density-matrix functional theory. Our scheme is based on a recent rigorous result on uniqueness of an effective impurity Anderson model which reproduces a positive-definite density–density correlation as well as the single electron density. A tractable algorithm to determine the U term using estimation of an impurity problem by the transcorrelated method is proposed. [Copyright &y& Elsevier]

Abstract: We show how correlation functions of the spin- Heisenberg chain without magnetic field in the anti-ferromagnetic ground state can be explicitly calculated using information contained in the quantum Knizhnik–Zamolodchikov equation [qKZ]. We find several fundamental relations which the inhomogeneous correlations should fulfill. On the other hand, it turns out that these relations can fix the form of the correlations uniquely. Actually, applying this idea, we have obtained all the correlation functions on five sites. Particularly by taking the homogeneous limit, we have got the analytic form of the fourth-neighbor pair correlator . [Copyright &y& Elsevier]

The magnetic drug delivery system (MDDS) is a key technology to reduce the side effects in the medical applications, and the magnetic force control is a very important issue in MDDS. In general, the high magnetic field along the axial direction and high magnetic field gradient along the longitudinal direction are very useful for MDDS. So, we proposed the new magnetic force control system that consists of superconducting magnet, high temperature superconductors (HTS) bulks or tapes and ferromagnetic substances. In this new system, the shielding currents in HTS bulks and tapes due to diamagnetism of the superconductor generate the magnetic field with same direction of external magnetic field, and we can control the magnetic field gradient along the longitudinal direction by the arrangement of the HTS bulks, tapes and ferromagnetic substances. In this study, the stacked GdBCO tapes without stabilizer were used in experiments and electromagnetic analysis based on finite element method (FEM) was carried out to optimize the arrangement of the superconductors and the irons. It was confirmed that the control of magnetic field gradient along the longitudinal direction was possible by arranging the HTS bulks, tapes and irons on the superconducting magnet and then it was possible to obtain a magnetic field higher than the external field. [ABSTRACT FROM AUTHOR]

Abstract: The effect of current sweep reversal on the temporal drift in magnetic field intensity for a Bi-2223 solenoid was investigated by experiment and using numerical simulation. Current sweep reversal, by as small as 1% of the peak current, was found to stabilize the drift in magnetic field intensity for a Bi-2223 tape solenoid. The field drift was due to flux creep in the Bi-2223 tape and the current sweep reversal formed a barrier for flux entrance at the upper and lower surface of the conductor, preventing flux creep. With a current reversal of several% of the peak current, the barrier formation extended over half of the solenoid and the magnetic field intensity became constant with time. The current sweep reversal technique should prove useful to stabilize an ultra-high field low/high-temperature superconducting nuclear magnetic resonance magnet operated at frequencies (field intensities) beyond 1GHz (23.5T). [Copyright &y& Elsevier]

Abstract: The screening current-induced magnetic field in the (Bi,Pb)2Sr2Ca2Cu3O x (Bi-2223) insert coil proposed for a beyond 1GHz nuclear magnetic resonance (NMR) spectrometer may generate a long-term field drift, resulting in a loss of field-frequency lock operation and an inability to make high resolution NMR measurements. The measured screening current-induced magnetic field of a Bi-2223 double-pancake coil exhibits a hysteresis effect at 4.2K that is reproduced by a numerical simulation based on a finite thickness rectangular superconductor bar model. The screening current-induced field at the coil center is of opposite polarity to that generated by the coil current, and thus the apparent field intensity shows a positive drift with time. On the contrary, the field at a coil end is of the same polarity as the coil field, and the apparent field intensity decreases with time. If we wait for ∼1000h after coil excitation, the field drift rate approaches the field decay rate of the persistent current of 10−8 h−1, suitable for a long-term NMR measurement in a beyond 1GHz NMR spectrometer. [Copyright &y& Elsevier]

Abstract: We report about the electron paramagnetic resonance and nuclear magnetic resonance signals in bulk and thin film-type ultrananocrystalline diamond with and without nitrogen. The localization and nature of defects for powder and compact film samples were analyzed. From the analysis of spin–lattice and spin–spin relaxation times, we have found that spin states sit in sp2 enriched region belonging to the grain boundaries. [Copyright &y& Elsevier]

Abstract: We investigated current transport properties in MgB2 wires subjected to transient application of magnetic field, and then discussed their applicability to magnetically controlled switching elements. These wires were fabricated by powder-in-tube (PIT) technique, and Cu–Ni as well as stainless was utilized for their sheath material. A short sample of the wire was installed in a Gifford–McMahon (GM) cryocooler, and was impregnated with solid nitrogen for the sake of thermal stabilization. After stabilizing the temperature of the sample at a certain bias current, the voltage and the temperature in between potential taps were monitored with a transient application of magnetic field. Such measurements were repeated systematically as functions of bias current, operating temperature and magnetic field intensity. It was shown that the sample quickly generated resistance without temperature increment by applying the transient and weak magnetic field. This indicates the applicability of MgB2 wires to persistent current switches (PCS) with quick response. [Copyright &y& Elsevier]

The effect of exchange field Hex on media properties and the dependence of Hex on composition of stabilizing layers and sputtering process in SF media have been examined. It is revealed that to increase Hex, it is necessary to increase the saturation magnetization of the ferromagnetic layers and to reduce the interface roughness. [Copyright &y& Elsevier]