Magnetic europium

A 100 MHz. proton magnetic resonance spectrum (chloroform d) of the amine in the presence of an equal amount of the chiral shift reagent, tris[3-(trifluoromethylhydroxymethylene)-d-camphorato]euro-pium(III)4 (submitters), or in the presence of an equal amount of tris[3-(heptafluoropropylhydroxymethylene)-d-camphorato]europium-(III) (checkers), revealed that the product contained no detectable enantiomeric isomer. 

More insight into the reasons for magnetism of derivatives may be obtained by a closer look at other recently discovered ferromagnetic Cjo materials, which include complexes of cobaltocene with a CgQ-derivative [156, 157], but also metal complexes with europium [175-177] or cerium [178-180] or pure C q in a polymeric modification [181-183]. 

Cario, L., Lefond, A., Palvadeau, A., Deudon, P., and Meerschault, C. (1999). Evidence of a mixed valence state for europium in the misfit layer compound [(EuS)i.5]i. i5NbS2 by means of a superspace structural determination, Mossbauer spectroscopy and magnetic measurements. /. Solid State Chem. 147, 58-67. 

All four terms have been observed empirically. Terms 1-3 are well known, and term 4 has been observed as a magnetization in europium ion doped glasses by van der Ziel et al. [37] as argued already. The RFR term therefore emerges self-consistently with three other well-known and well-observed terms from what is effectively the 0(3) covariant derivative. 

The single-bond radii for the lanthanons (La to Lu, Fig. 11-10) show some interesting features. The magnetic properties26 require that most of the lanthanons have metallic valence 3, but that two of these metals, europium and ytterbium, have metallic valence 2. The interatomic distances reflect these valences dearly, as shown in Figure 11-10. The stability of metallic valence 2, rather than 3, for these two metals may be attributed to the special stability of a half-filled or completely filled 4/ subshell. 

Table 9. Magnetic susceptibility X atom of europium at different temperatures [160]...

The readers will undoubtedly agree that the elucidations and derivations of the equations 13—15 are beyond the scope of this book, but chemists with some physical inclination may find some satisfaction in reading through Van Vleck s [207] Theory of Electric and Magnetic Susceptibilities to quench their mathemetical thirst. Instead of tabulating the measured magnetic moments of all europium compounds with variations we will mention the magnetic behaviour of the individual compounds as we deal with them. 

In 1939 Klemm and Doll [276] prepared all the halides of divalent europium and studied the magnetic characteristics of these compounds. The magnetic susceptibilities (X g) and effective moments of the fluoride, chloride, bromide and iodide are tabulated in Table 15. Except for the... 

Reaction of metallic europium with cyclopentadiene in liquid ammonia yields [478] a yellow europous-dicyclopentadienyl (eq. 41) complex. Magnetic measurements on this compound (jn = 7.62 Bohr magneton) and its infrared spectrum definitely confirm the divalent state of europium. 

K. The stable antiferromagnetic ground state was also evident from the negative Weiss constant of —14 K and the monotonically increasing magnetization curve with a value of 2.8 p.b/Eu at 2 K and 5.5 T.151 Eu Mossbauer spectroscopic studies confirmed the divalent nature of europium in EuAuPb with an isomer shift value of —10.9 mm/s at 78 K. Line broadening in the Mossbauer spectra occurred around... 

Nine derivatives of 1, [RSb9W2i086]16 (R = La-Gd, Dy, Yb), have been isolated and characterized by elemental analysis, magnetic susceptibility, and infrared spectra. The four-line 183W-NMR spectrum of the lanthanum derivative is consistent with the D3h symmetry of the parent structure, but the emission spectrum of the europium derivative suggests a lower symmetry in the solid state (Liu et al., 1992). No structural determinations of these derivatives have yet been reported. 

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