Measurements magnetic

Prepare or use a magnetic susceptibility standard in the Gouy balance or the Evans instrument. Use the standard to find the constant C in the eqn. 2.6 or C in eqn. 2.11. Grind each of the prepared complexes to a fine powder. Pack the balance tube with the powder to the mark and follow the instructions as in Sec.2.1.3. Calculate the magnetic susceptibility and the effective magnetic moment of each powder and comment on your results. 

With ferromagnetic metals that exhibit superparamagnetism, magnetic measurements can also be used to calculate particle size [2,4,21]. For example, the low-field and high-field Langevin equations were used to analyze the magnetization behavior of Fe particles dispersed on carbon, and the results indicated the presence of 2-4 nm Fe crystallites, a size range consistent with previous measurements [22]. 

For liquid samples contained in a cell, it is necessary to measure the total magnetization of sample and cell and then correct for the separately measured magnetization of the cell. Considerable care is required because the cell magnetization can easily exceed that of the sample by a large factor. Cells for susceptibility measurements may be either metallic or insulating so a relatively wide choice of materials is avail- 

Because of the relatively small outer diameter of an NMR autoclave, the insulation separating the heating elements from the inner wall of the pressure vessel is of critical importance. This insulation must meet the conflicting requirements of low thermal conductivity and low permeabU-ity to convection in the pressure medium. In one scheme, the insulation consists of a layered structure formed by a roll of 0.025 mm molybdenum foil. The layers were separated with small spacing by 0.05 mm pimples embossed on the foil. With this insulation, a sample temperature of 1500 =C at 90 bar can be obtained with 450 W of DC power. A more efficient, but slightly more complex variation uses layers of molybdenum foil separated by thin sheets of alumina cloth. 

Cells containing the bulk NMR samples must be electrically insulating so that the applied radio-frequency fields can couple to the material within. Suitable cell materials for high temperature use include alumina ceramic, single crystal sapphire, boron nitride, yttria, etc. Zirconia is not acceptable because of its high ionic conductivity at elevated temperatures. Sample containment is most critical for experiments on alkali metals because of their extreme corrosivity at high temperatures. Sapphire has been found to be the best available insulating material for studies of liquid cesium. 

3 About the Chemical Composition of Cei xCax02 x and Cei xCaxOi-x-y/iFy Series 

The F/Ce atomic ratio in Table 8.2 increases with the Ca/Ce atomic ratio in good agreement with the affinity of fluorine for calcium atoms. But whereas the F/Ca precursor atomic ratio is equal to 2, the F/Ca atomic ratio in the final product is always lower than 1. 

In the oxyfluoride series, two samples F6 and F7 have the same Ca/Ce atomic ratio (0.40) but the F/Ce atomic ratio is higher for F7 (0.52) leading to a mixture of Ca-Ce oxyfluorides and CaF2- In the case of F6, CaF2 was not detected as in the other oxyfluorides with lower Ca contents. This difference illustrates the importance of the duration of the maturation of the oxyhydroxides 3 h for F7 and 20 h for F6. In the former conditions. 

Sample Ca/Ce precursor atomic ratio Ca/Ce final atomic ratio Na/Ce final atomic ratio 

Sample Ca/Ce precursor Ca/Ce final Na/Ce final F/Ce final atomic 

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Correlation between the body forces and the stress state in the head was investigated both by the strain gauge method and the optical coat work stress examination method, and the magnetic measurements were performed at the same time. 

W R McLean. Apparatus for Magnetically Measuring Thickness of Ferrous Pipes US Patent. 6 Nov 51... 

Other magnetic measurements of catalysts include electron paramagnetic resonance and magnetic susceptibility. Although those are not as common as NMR, they can be used to look at the properties of paramagnetic and ferromagnetic samples. Examples of these applications can be found in the literature [87. 

In shock-compression science the scientific interest is not so much in the study of waves themselves but in the use of the waves as a means to probe solid materials. As inertial responses to the loading, the waves contain detailed information describing the mechanical, physical, and chemical properties and processes in the unusual states encountered. Physical and chemical changes may be probed further with optical, electrical, or magnetic measurements, but the behaviors are intimately intertwined with the mechanical aspects of the waves. 

Electronic Properties of Carbon Nanotubes Probed by Magnetic Measurements... 

Here, we review the electronic properties of MWCNT and SWCNT probed by magnetic measurements. MWCNTs are discussed with a classification of the following four categories (1) crude CNTs, (2) purified CNTs, (3) aligned CNTs and (4) alkali-doped CNTs. 

Since electron spin resonance (ESR) measurements are mainly focused as a probe of the electronic properties of CNTs in this report, the basis of magnetic measurements is briefly mentioned in this chapter. 

Lastly, we discuss electronic properties by other measurements in comparison with that by magnetic measurements. 

These results are consistent with the electronic properties of CNTs probed by magnetic measurements. In sum, most of MWCNTs show semimetallic behaviour experimentally. 

We have reviewed the electronic properties of CNTs probed by magnetic measurements. MW- and SWCNTs can individually be produced, however, the parameters of CNTs are uncontrollable, such as diameter, length, chirality and so on, at the present stage. Since the features of CNTs may depend on the synthesis and purification methods, some different experimental observation on CNT properties has been reported. It is important, however, that most of papers have clarified metallic CNTs are actually present in both MW- and SWCNTs. The characteristic of CESR of SWCNTs is different from that on non-annealed MWCNTs, but rather similar to that on annealed multi-walled ones. The relationship of the electronic properties between SW- and MWCNTs has not yet been fully understood. The accurate control in parameter of CNTs is necessary in order to discuss more details of CNTs in future. 

The crosslinking reaction is detectable without difficulty by spectroscopic and magnetic measurements. 

The study of ultra-thin Fe thin films on Cu(OOl) substrate has attracted a lot of interest in the past. This is due to the abundance of interesting phenomena associated with this system. Due to the small epitaxial misfit a good layer by layer growth is expected stabilizing the film in a structure related to the fee phase of bulk Fe which is otherwise unstable at low temperatures It also become a test system for magnetic measurements. 

Product yields may also be determined by magnetic measurements, as in the formation of ferrites [340], where kinetic data were obtained at reaction temperature. Quantitative applications of Mossbauer spectroscopy have also been described [326]. 

The l/x vs-T plot is shown in Fig. 1. It should be noted that the same set of parameters fits all six expected transitions of the optical spectrum. For Pu(VII) this is the only known magnetic measurement in the temperature range between 4 and 300 K. 

No magnetic measurements for compounds of pentavalent plutonium have been reported so far. 

Magnetic measurements of PuFi, between 4.2 and 300 K are consistent at high temperatures with older measurements (10-12). The large temperature dependent diamagnetism observed earlier was not found. Up to 100 K the susceptibility is nearly temperature independent with a value of X ip 2940 x 10-6 emu. The Curie-Weiss behavior near room temperature indicates population of a higher first excited state. The structure of PuFi, is isomorphic with that of UFi, (13), where two different sets of actinide atoms are 8-fold coordinated by a distorted antiprism. 

That magnetic measurements often raise more problems than they solve, is demonstrated for the indicated compound. We prepared a series of [ (C2H5N] i,An(NSC) e compounds (An = Th, U, Np, Pu) with cubic coordination of the actinide ion. We derived a consistent interpretation of the magnetic and optical properties of the uranium and the neptunium compounds (6 ). In the case of Pu we expect an isolated T1 ground state and a first excited state at about 728 cm-1. To our surprise we found a magnetic ground state much more pronounced than in the case of the hexachloro-complex, Fig. 4. 

From magnetic measurements on the elpasolite Cs2NaPuCl6 a Te ground state and a low lying F7 state was deduced (26). The magnetic moment varies from 0.65 at 3 K to 1.1 lig at 50 K. 

These magnetic measurements indicate that plutonium is present as the +3 valence in these compounds. Pu3+ has a 5f5 configuration, and ground state, and would show Curie-Weiss paramagne-... 

Lithium oxides of Pu, magnetic measurements and reciprocal molar susceptibility vs. 

The effects of the bonding electrons upon the d electrons is addressed within the subjects we call crystal-field theory (CFT) or ligand-field theory (LFT). They are concerned with the J-electron properties that we observe in spectral and magnetic measurements. This subject will keep us busy for some while. We shall return to the effects of the d electrons on bonding much later, in Chapter 7. 

Rare-earth ions inserted in the tetraborides have the 34- oxidation state, except for CeB4 and YbB4 (see Fig. 2). The abnormal volume contraction for the CeB4 unit cell can be explained by the presence of some Ce ions . Recoilless y-ray emission spectra and magnetic measurements indicate that ytterbium in YbB4 has an intermediate valence state as in YbAl3... 

Ionic polysulfides dissolve in DMF, DMSO, and HMPA to give air-sensitive colored solutions. Chivers and Drummond [88] were the first to identify the blue 83 radical anion as the species responsible for the characteristic absorption at 620 nm of solutions of alkali polysulfides in HMPA and similar systems while numerous previous authors had proposed other anions or even neutral sulfur molecules (for a survey of these publications, see [88]). The blue radical anion is evidently formed by reactions according to Eqs. (5)-(8) since the composition of the dissolved sodium polysulfide could be varied between Na2S3 and NaaS with little impact on the visible absorption spectrum. On cooling the color of these solutions changes via green to yellow due to dimerization of the radicals which have been detected by magnetic measurements, ESR, UV-Vis, infrared and resonance Raman spectra [84, 86, 88, 89] see later. 

The limited magnetic measurements of very mixed -metal clusters are summarized in Table XIII. The magnetic behavior of some anti-ferromagnetic very mixed -metal carbonyl clusters (Fig. 82) has been studied by Pasynskii and eo-workers. Temperature dependences of the magnetic susceptibilities of Cr2Co(/t3-S)3(/i-SBu )(CO)2() -C3H4R)2l (R = H. Me) have been determined us-... 

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