Topic
Relaxation (NMR)
About: Relaxation (NMR) is a research topic. Over the lifetime, 29342 publications have been published within this topic receiving 689851 citations.
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TL;DR: Three types of biosensors that employ different biosensing principles, magnetic materials, and instrumentation are covered, which consist of magnetic relaxation switch assay-sensors, which are based on the effects magnetic particles exert on water proton relaxation rates.
Abstract: Many types of biosensors employ magnetic nanoparticles (diameter = 5–300 nm) or magnetic particles (diameter = 300–5,000 nm) which have been surface functionalized to recognize specific molecular targets. Here we cover three types of biosensors that employ different biosensing principles, magnetic materials, and instrumentation. The first type consists of magnetic relaxation switch assay-sensors, which are based on the effects magnetic particles exert on water proton relaxation rates. The second type consists of magnetic particle relaxation sensors, which determine the relaxation of the magnetic moment within the magnetic particle. The third type is magnetoresistive sensors, which detect the presence of magnetic particles on the surface of electronic devices that are sensitive to changes in magnetic fields on their surface. Recent improvements in the design of magnetic nanoparticles (and magnetic particles), together with improvements in instrumentation, suggest that magnetic material-based biosensors may become widely used in the future.
282 citations
TL;DR: A new technique to measure conduction electron relaxation times is described, using nonequilibrium magnetization present in a paramagnetic metal can be detected as an open circuit voltage across an interface between the paramagnet and a ferromagnet.
Abstract: Microscopic models are presented to elucidate the concept of interfacial charge-spin coupling. At the interface between a ferromagnet and a paramagnet, the spin subbands are loosely coupled, an interfacial conductance may be defined for each, and a result of their inequivalence is that an electric current flowing from a ferromagnetic metal into a paramagnetic metal will be partially spin polarized, i.e., will have an associated current of magnetization. The inverse is also true; nonequilibrium magnetization present in a paramagnetic metal can be detected as an open circuit voltage across an interface between the paramagnet and a ferromagnet. Using this effect, a new technique to measure conduction electron relaxation times is described.
282 citations
TL;DR: It is found that for accessible electron densities in the usual three-dimensional metallic systems the scattering time is at most a factor of \ensuremath{\sim}2 larger than the single-particle relaxation time whereas in high-mobility GaAs-based heterojunctions the spatial separation between the impurities and the carriers gives rise to scattering times which can be as much as two orders of magnitude larger.
Abstract: Relative magnitudes of the single-particle relaxation time and the scattering time that enters in conductivity are given for two- and three-dimensional electron gases in the presence of random distributions of charged Coulomb scattering centers. We find that for accessible electron densities in the usual three-dimensional metallic systems the scattering time is at most a factor of \ensuremath{\sim}2 larger than the single-particle relaxation time whereas in high-mobility GaAs-based heterojunctions the spatial separation between the impurities and the carriers gives rise to scattering times which can be as much as two orders of magnitude larger than the corresponding single-particle relaxation times.
281 citations
TL;DR: An overview of the influence of inter-particle interactions on the properties of magnetic nanoparticles and the temperature dependence of the order parameter in samples of strongly interacting hematite nanoparticles or goethite grains is presented.
Abstract: We present a short overview of the influence of inter-particle interactions on the properties of magnetic nanoparticles. Strong magnetic dipole interactions between ferromagnetic or ferrimagnetic particles, that would be superparamagnetic if isolated, can result in a collective state of nanoparticles. This collective state has many similarities to spin-glasses. In samples of aggregated magnetic nanoparticles, exchange interactions are often important and this can also lead to a strong suppression of superparamagnetic relaxation. The temperature dependence of the order parameter in samples of strongly interacting hematite nanoparticles or goethite grains is well described by a simple mean field model. Exchange interactions between nanoparticles with different orientations of the easy axes can also result in a rotation of the sub-lattice magnetization directions.
281 citations
Book•
13 Sep 2014
TL;DR: In this paper, the authors derived the equations for contact shift and relaxation in a simple case and derived the pseudocontact shift in the case of axial symmetry, and derived Curie's law.
Abstract: Selected Contents. Introduction. The hyperfine shift. Relaxation. Chemical exchange, chemical equilibria and dynamics. Transition metal ions: shift and relaxation. Magnetic coupled systems. Nuclear Overhauser effect. Two-dimensional spectra and beyond. Hints on experimental techniques. Appendix I NMR properties of nuclei. Appendix II Dipolar coupling between two spins. Appendix III Derivation of the equations for contact shift and relaxation in a simple case. Appendix IV Derivation of pseudocontact shift in the case of axial symmetry. Appendix V Relaxation by dipolar interaction between two spins. Appendix VI Calculation of (Sz): Curie's law. Appendix VII Derivation of the equations related to NOE. Appendix VIII Magnetically coupled dimers in the high-temperature limit. Appendix IX Product operators: basic tools. Appendix X Reference tables. Subject index.
279 citations