Diamagnetic susceptibility temperature dependence

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. 

With respect to the physical properties mentioned, band-structure calculations have attracted considerable interest, e.g., for SbSBr, SbSI, and SbSel (234). For the compounds having reference 22i in column 4 of Table XXIX, a temperature-independent diamagnetism has been found, with values of about 10 cm" g between 77 and 340 K. A small temperature-dependence is exhibited by BiTel, a narrow-gap semiconductor (41). The anisotropy of the magnetic susceptibility has been studied for SbSI, BiSel, and BiTel (41, 420). 

Fig. 7 Temperature dependence of the static magnetic susceptibility of (a) (EDT-TTFBr2)2 FeBr4 (b) (EDO-TTFBr2)2FeCl4 (c) (EDO-TTFBr2)2FeBr4 measured at an external field of B = 1 T after the core diamagnetic contributions are subtracted...

Clark and Odell have found (39) that the susceptibility varies with temperature in a way that can be explained very well on the basis of temperature-dependent equilibria between diamagnetic and paramagnetic forms. This is valid equally for pyridine and for inert solvents. Thermodynamic quantities calculated from these measurements show that the paramagnetic forms have the lower enthalpies, and that there are relatively large increases of entropy on going from the paramagnetic to the diamagnetic forms. 

The determination of n from measurement of peff is the most familiar application of magnetic susceptibility measurements to inorganic chemists. To the extent that the spin-only formula is valid, it is possible to obtain the oxidation state of the central atom in a complex. Thus an iron complex with a peff of 5.9B.M. certainly contains Fe(III) (high-spin d5) and not Fe(II). The diamagnetism of AgO rules out its formulation as silver(II) oxide, because Ag2+ has an odd number of electrons (d9) and should be paramagnetic it contains Ag(I) and Ag(III), in equal amounts. There are, however, a number of pitfalls, especially if reliance is placed on a single measurement at room temperature. The Curie law is rarely obeyed within the limits of experimental error. This means that the measured peff is somewhat temperature-dependent. A number of factors can be responsible for deviations from ideal Curie (or even Curie-Weiss) behaviour, and/or from the spin-only formula. 

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... 

Neglecting the third term of Eq. (12), the mass susceptibility of a paramagnetic solute is readily determined from m and Ai. The diamagnetic mass susceptibilities 0 of the solvents, in SI units of m kg are -8.8 X 10 (benzene), —9.0 X 10 (toluene), and -9.0 X 10 (t-butyl alcohol-water solvent). For temperature-dependence studies, correct m according to Eq. (18), calculate A A/and plot versus HT. The slope of the best straight... 

For X < 0.4, the magnetic susceptibility is temperature dependent like that of pure palladium, but it has lower values. For x > 0.6, this temperature dependence disappears and the system is diamagnetic (60), like that of silver, a neighbor of Pd in the periodic table. This change is related to a change in position of the Fermi level with respect to the d-band. For low X the Fermi level crosses the d-band, as in pure Pd (cf. Fig. 9) at x 1, Ef is above the d-band (Fig. 21a) (61). When the H/Pd ratio increases, the total DOS at Ef (and therefore the susceptibility) decreases, but it is calculated that the LDOS at Ef on the hydrogen site should increase (62) (Fig. 21b). 

The interaction of the carbon dioxide molecule with the sieve includes electrostatic, induction, dispersion, and repulsion contributions. The CO2 molecule was assumed to be capable of free rotation, so that the directional interactions could be averaged over all orientations using a Boltzmann weighting factor (JJ) this causes the electrostatic ion-quadrupole interaction to depend on the temperature. Mean values were used for the polarizability (a), the diamagnetic susceptibility (x), and the equilibrium radius of the CO2 molecule. Using vector summation for the total electric field at the CO2 molecule, the total potential, c(r), at a given position r is given by ... 

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