Atoms paramagnetic

The term ferromagnetism reflects the fact that iron shows this effect, but it is by no means restricted to iron or iron compounds. Ferromagnetism is a cooperative phenomenon, i.e. many particles in a solid behave in a coupled manner. Paramagnetic atoms or ions exert influence on each other over extended regions. 

The magnetic specific heats of some alloys containing paramagnetic atoms together with copper for comparison are shown in Fig. 3.8. Note that below 0.1 K, magnetic materials as manganin have a specific heat 103 higher than copper. 

The electronic ground state for the oxygen atom is 3P2, which is consistent with two unpaired electrons in the 2p4 configuration. Unlike most molecules composed of two paramagnetic atoms, the 02 molecule is also paramagnetic. Although the structure has been shown as... 

Phosphorus is paramagnetic, because a paramagnetic atom is defined as having magnetic properties caused by unpaired electrons. The unpaired electrons are found in the 3p orbitals, each of which is half-filled. 

In the EXAFS and Electron Energy Loss Spectroscopy (EELS) spectra [11] show no trace of Co oxide, however XAS spectra of the smallest particles present characteristic peaks of CoO bonds in the L3 contribution. The fraction of Co bonded to oxygen atoms is proportional to the fraction of paramagnetic atoms, or very small clusters. However, for (d > 2 nm this... 

Besides, in the same L3 spectra it can be observed that the lines narrow and split into two as the diameter decreases. A possible origin of split lines is the presence of CoO in the paramagnetic atoms. Indeed, the split lines can be understood in terms of the 3d electrons in the smallest clusters (less than 10 atoms) tending to atomic like (discrete) spectra, similar to the features... 

Similarly, when a paramagnetic atom or molecule with magnetic moment ft, is placed in an external magnetic field B0, the orientational potential energy is ... 

Proton NMR by pulsed techniques to permit the study of relaxation effects provides information on the distribution of protons, and thus of water molecules, between different environments. An early study (S81) indicated that, at RH < 70%, the evaporable water in hep was in an environment similar to that of the interlayer water in clay minerals or in certain crystalline hydrates. Subsequent work (B111,M71,M72,S82) has given indications of the distributions of both chemically bound and unbound water among a number of environments. The method, which can be applied most effectively only to materials very low in paramagnetic atoms (including iron), has so far been used primarily to follow the course of hydration, but it would appear that it could also provide much information on pore structure. 

A paramagnetic atom with Td symmetry should give only one resonance line, but when this atom has a nuclear spin, the electron and nuclear spins can couple by hyperfine interaction, and for a nuclear spin I, each electronic spin component splits into 21+1 components giving the same number of Am/ = 0 resonances. For instance, the ESR spectrum of tetrahedral interstitial Al I = 5/2) produced by electron irradiation of AZ-doped silicon is an isotropic sextuplet due to transitions between the six nuclear sublevels of each electronic-spin component ([54], and references therein). The electron spin of a centre can also interact with the nuclear spins of neighbouring atoms to give additional structures and this is clearly shown for 29 Si atoms (I = 1/2) in Fig. 4 of [54]. The ESR spectrum can thus also determine the atomic structure of the centre. This can also occur for non-cubic centres and the hyperfine structure is superimposed on the orientational structure. 

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