Metal external magnetic field

Fig. 7.17 Time evolution of the nuclear forward scattering for metallic Ni foil. All measurements except for the upper curve were performed with external magnetic field B = 4 T. The solid lines show the fit. The arrows emphasize stretching of the dynamical beat structure by the applied magnetic field. The data at times below 14.6 ns had to be rescaled (from [34])...

ENDOR experiments can be performed in liquid solution, in which only the isotropic hfc s (Ajso) are detected. They are proportional to the spin density at the respective nucleus. Erom the assigned isotropic hfc s a map of the spin density distribution over the molecule can be obtained. In frozen solutions and powders the anisotropic hf interactions can also be determined. Eurthermore, the method allows the detection of nuclear quadrupole couplings for nuclei with 1 1. For dominant g anisotropy as found in many metal complexes the external magnetic field can be set to several specific g values in the EPR, thereby selecting only those molecules that have their g tensor axis along the chosen field direction. In such orientation-selected spectra only those hf components are selected that correspond to this molecular orientation ( single crystal-like ENDOR ). 

For a description of the electron-counting procedure as applied to metal clusters, see Ref 37.) The paramagnetism of the nickel cluster, in principle, could be detected directly by neutron diffraction with a polarized beam and an external magnetic field. However, such measurements were not undertaken, and the effects of paramagnetism on the observed diffraction intensities, that are small in the present experiment, were ignored. 

If one of the metals (commonly referred to as superconductors) is castin the form of a ring and an external magnetic field is applied perpendicularly to its plane and then removed, a current will flow round the ring induced by-Faraday induction. This current will produce a magnetic field, proportional to the current, and the size of the current may be observed by measuring dm field. Were the ring (e g., one made of lead) at a temperature above 7.2 K, this current and field would decay to zero in a fraction of a second. 

Conductor-Superconductor Transition When some metals or compounds are cooled below a certain temperature, their electrical resistance drops abruptly to zero. This temperature is referred to as the superconducting transition temperature. These materials are classified into two categories, type I or type II superconductors, depending upon how a bulk sample behaves in an external magnetic field. In the absence of an external magnetic field, the (superconductor + normal) transition is continuous in both types of superconductors. When a magnetic field is applied, the transition becomes first order in type I superconductors, but remains continuous in the type II superconductors. 

Fig. 2.5. A molecule possessing magnetic anisotropy, with the z axis oriented along the external magnetic field and a nucleus having a metal-nucleus vector at an angle y with the external magnetic field.

From the above information it appears that high spin iron(III) is not an ideal metal ion to be studied by high resolution NMR because of the dramatic effects on linewidths. In small complexes, xr may be the correlation time especially if it is considered that r may increase with the external magnetic field [14]. 

The magnetic moment of the 4s-valence electron of a chromium and a copper atom is cancelled out by the magnetic moment of a neighbouring atom s valence electron. All atoms in the table, except for copper, have unpaired electrons in d-orbits due to which you would expect a magnetic moment. They exhibit this behaviour when they are placed in an external magnetic field. As soon as this external magnetic field is switched off, the magnetism in the metals disappears. 

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