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Magnetic Field Dependence (magnetic + field_dependence)
Selected AbstractsRheological properties of magnetic fluids and their microstructural backgroundGAMM - MITTEILUNGEN, Issue 1 2007S. Odenbach Abstract Beyond the changes exerted by magnetic fields on the flows and properties of suspensions of magnetic nanoparticles, the change of their viscous behavior attracts ongoing research interest since nearly four decades. Within this contribution we'll review the general rheological features of ferrofluids and will present theoretical explanations on microstructural basis providing an insight in the mechanisms leading to a magnetic field dependence of ferrofluid's rheology. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The apparent dependence of the diffusion coefficient of N-acetylaspartate upon magnetic field strength: evidence of an interaction with NMR methodologyNMR IN BIOMEDICINE, Issue 8 2003David N. Guilfoyle Abstract An inverse relationship between applied magnetic field strength and the apparent diffusion coefficient (ADC) of several important brain metabolites including N -acetyl- l -aspartate (NAA), choline and creatine, measured in vivo using proton magnetic resonance spectroscopy (MRS), has been reported. In this investigation, using phantom studies of NAA at magnetic field strengths of 3 and 7,T, these observations have been verified under controlled MRS conditions in vitro, and the ADC of NAA has been found to vary inversely with magnetic field strength, decreasing at a rate of 2.5%/T at 20°C. We have also assessed whether the effect is a function of a systemic bias in methodology, or if the effect is actually on the rate of molecular diffusion. This was done using an MRS-independent method for measurement of molecular diffusion in NAA phantoms at 0, 0.025 and 7,T applied magnetic field strengths. As a result, it has been demonstrated that the observed apparent magnetic field dependence of the ADC of NAA is a consequence of the NMR measurement and is apparently not a real effect on molecular diffusion. Copyright © 2003 John Wiley & Sons, Ltd. [source] Magnetoresistance, transport noise and granular structure in polycrystalline superconductorsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2007I. García-Fornaris Abstract In this work we present a theoretical study on the magnetic field dependence of the electrical resistance R (Ba) and the transport noise (TN) in a high- Tc polycrystalline superconductors. In the model, we have considered the ceramic superconductor as a series-parallel array of Josephson devices and the intergranular magnetic field is described within the framework of the intragranular flux-trapping model. The obtained results qualitatively reproduce the hysteretic behavior of the R (Ba) dependence in increasing and decreasing applied magnetic fields. We have found that the hysteretic behavior in the R (Ba) dependence changes appreciably if different statistical distributions of the geometric factors of grains are used. In addition, such changes are also reflected in the TN, which is produced by the electric current rearrangement in the array with increasing applied magnetic fields. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Special type of surface states in Hg1,xCdxTePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2010Salim Gasan-zade Abstract Recently, it was shown that, in the Hg1,xCdxTe compound, the photoelectromagnetic effect (PME) exhibits some specific features and anomalies. The anomalies manifest themselves in the alternating sign behavior (including double sign reversal) of the photomagnetic current JPME in the magnetic field H. In this case, both the sign and shape of the magnetic field dependence of the PME current is critically dependent on the intensity of external excitation radiation and the temperature of the sample. In this work, we demonstrate that the anomalies are determined by hitherto unknown surface states. [source] Aharonov,Bohm effects in multiwall carbon nanotubesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 13 2006C. Strunk Abstract We investigate quantum transport phenomena in multiwall carbon nanotubes in perpendicular and parallel magnetic field. An efficient gating technique allows for a considerable tuning of the nanotube doping level. We show that the weak localization is strongly suppressed at peaks at certain gate voltages which can be linked with the bottoms of one-dimensional electronic subbands. In large parallel magnetic field, we observe a superposition of h /2e -periodic Altshuler-Aronov-Spivak oscillations and an additional h /e -periodic contribution, which we attribute to the magnetic field dependence of the band structure. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Transport properties of hydrogen-doped (Zr803d20)1,xHx (3d = Co, Ni) metallic glassesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2004I. Kokanovi Abstract The electrical resistivities of hydrogen-doped (Zr803d20)1,xHx (3d = Ni, Co; x , 0.11) metallic glasses have been measured at temperatures between 2 K and 110 K and in magnetic fields up to 1 T for various dopant concentrations. These systems have a high room-temperature resistivity (, > 160 ,, cm) and become superconducting below 4 K. The increase of the room-temperature resistivity and its temperature coefficient with hydrogen dopant concentration is explained as due to an increase of disorder with hydrogen-doping. The temperature and magnetic field dependence of the resistivity has been analysed using theoretical models of weak-localisation and electron,electron interaction in disordered conductors. The hydrogen dopant is found to reduce the effective electron diffusion constant, D, the spin-orbit scattering rate, ,,1so, the superconducting transition temperature, Tc, and broadens the superconducting transition region. The contribution of the Maki-Thompson interaction to the magnetoresistivity is also reduced. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optical spin orientation of a single manganese atomPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2010C. Le Gall Abstract An optical spin orientation is achieved for a Mn atom localized in a semiconductor quantum dot using quasiresonant excitation at zero magnetic field. Optically created spin polarized carriers generate an energy splitting of the Mn spin and enable magnetic moment orientation controlled by the photon helicity and energy. The dynamics and the magnetic field dependence of the optical pumping mechanism shows that the spin lifetime of an isolated Mn atom at zero magnetic field is controlled by a magnetic anisotropy induced by the built-in strain in the quantum dots. Relaxation times exceeding the micro-second range are measured (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Hopping magnetoresistance in two-dimensional arrays of Ge/Si quantum dotsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2006A. I. Yakimov Abstract The temperature and magnetic field dependences of the conductivity associated with hopping transport of holes over 2D arrays of Ge/Si quantum dots with various filling factors are studied experimentally. A transition from the Efros-Shklovskii law for the temperature dependence of hopping conductivity to the Arrhenius law with an activation energy equal to 1.0-1.2 meV is observed upon a decrease in temperature. The activation energy for the low-temperature conductivity increases with the magnetic field and attains saturation in fields exceeding 4 T. It is found that the magnetoresistance in layers of quantum dots is essentially anisotropic: the conductivity decreases in magnetic fields oriented perpendicular to a dot layer and increases in a field whose vector lies in the plane of the sample. The absolute values of magnetoresistance for transverse and longitudinal field orientations differ by two orders of magnitude. Effect of spin correlations on the hopping magnetoresistance is discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||