Samarium magnetic susceptibility

Figure 9.17 Plot of the in-phase and out-of-phase AC magnetic susceptibility for the complex [SmFe] at driving frequency of 199 Hz and 355 Hz [98]. (Reprinted with permission from B. Yan, and Z. Chen, Cyano-bridged aqua(A, Al-dimethylacetamide)(cyanoiron)lanthanides from samarium, gadolinium, or holmium nitrate and potassium hexacyanoferrate crystal structures and magnetochemistry, Helvetica Chimica Acta, 2001, 84, 817-829 (Figure 7). Wiley-VCH Verlag GmbH Co. KGaA.)...

The results show that the magnetic susceptibility of these carbides agrees well with a Curie-Weiss law of the form X = Xq + (C/T — 0 ) above the temperature T. The only exception is samarium hypocarbide, for which a deviation from this law has been observed. This type of deviation also occurs in SmC2 and has been attributed to Van Vleck paramagnetism. 

Grignard type compounds of some lanthanide metals in the oxidation state +2 have been investigated by D.F. Evans et al. (1970, 1971). Europium, samarium and ytterbium react in tetrahydrofuran with alkyl and aryl iodides between —20 and + 30°C forming colored solutions containing mixtures of compounds, which give some Grignard-type reactions. Characterization of the compounds was done only by magnetic susceptibility measurements and some titrimetric analyses. 

D.F.Evans prepared divalent organo ytterbium for the first time by the reaction of ytterbium metal with organic halides in THF at - 20 C. Magnetic susceptibility measurements showed that 75-92% of the ytterbium is present in the divalent state. Samarium reacts more slowly, giving a mixture of divalent and trivalent species, as expected from the greater instability of the divalent state when Sm is compared to Yb (30). These solutions give Grignard-like reactions for example, PhSmI reacts with benzophenone to afford Ph C(OH) in 72% yield. 

Kohler and Muller (1991) obtained a divalent samarium fluoroaluminate, LiSm-AlFg, by heating a confined mixture of the appropriate fluorides two days at < 700°C. In contrast to the structure of the closely related strontium and calcium analogues in which the divalent cation is coordinated octahedrally, the Sm ion coordination is trigonal prismatic. Magnetic-susceptibility measurements show temperature dependence typical of divalent samarium. 

In SmRu2Si2, the effective paramagnetic moment is only 0.54/ig. It corresponds to 7 = 5/2 ground level for free Sm and a low lying excited level with 7 = 7/2. At the temperatures above 15 K the magnetic susceptibility as a function of temperature follows the Van Vleck function for the free Sm ion (Hiebl et al. 1983). In SmRu2Ge2 a small part of samarium moments 0.23(10) /Xg orders magnetically below 10 K (Felner and Nowik 1985). 

In the case of Eu and Yb the reactions proceed at temperatures ranging from -40 to -20 C. Samarium is less active and after an activation by treatment with iodine interacts with RI at 30 C to give blue-green solutions of RSml. The solutions of Eu and Yb derivatives are brown. The products were not isolated from the reaction mixture as individual compounds, however the formation of them is reliably confirmed by the data of acidimetry and iodometry, reactions with iodine, as well as by reactions characteristic for Grignard reagents with Michler s ketone, water, benzophenone, Me3SiCl. The measurement of magnetic susceptibility has shown that in the Eu and Yb complexes from 85 to 100% of the metal is in bivalent state. In the Sm complexes up to 50% of the metal is present as Sm(III). 

The structure and magnetic properties of samarium as the sesquioxide and the metal have been studied by Perakis and Kern (1972). Between 8(1-154 K the magnetic susceptibility of a purified Sm specimen essentially coincided with that for Sm " in monoclinic Sm203. The minimum of x (the magnetic susceptibility) was at about 350 K. 

Thus magnetic susceptibility measurements provide an interesting means of evaluating percentages of Ln and Ln + ions in a mixture of species. Effective magnetic moments of divalent samarium and ytterbium compounds are listed in table 5. 

For SmCj, as mentioned above, the reciprocal susceptibility does not obey the Curie-Weiss law above the Neel temperature of 21 K (Sakai et al. 1981a) in contrast to the results of Vickery et al. (1959). This anomalous magnetic behavior resembles that reported for other samarium compounds and seems to be attributed to the contribution of the first excited multiplet state (J = j) to the value. 

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