Temperature dependence diamagnetism

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. 

The magnetic properties of Pu(CeHe)2 (=Pu(C0T)2), Pu(C2HsC0T)2 and Pu(CifH9C0T)2 were measured by Karraker (17,18). All compounds proved to be diamagnetic at room temperature near the theoretically calculated diamagnetic value. At low temperature they showed strong temperature dependent diamagnetism from -5,000 x 10-6 emu at 4 K to -900 x 10 6 emu at 45 K. 

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... 

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...

It is now well known that many diamagnetic, square-planar nickel(II) chelates develop temperature-dependent paramagnetic moments in solution. The subject was last reviewed by Sacconi (221) in 1959, but later developments make a further summary worthwhile. 

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. 

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