Samarium magnetic properties

The valences of the rare-earth metals are calculated from their magnetic properties, as reported by Klemm and Bommer.14 It is from the fine work of these investigators that the lattice constants of the rare-earth metals have in the main been taken. The metals lutecium and ytterbium have only a very small paramagnetism, indicating a completed 4/ subshell and hence the valences 3 and 2, respectively (with not over 3% of trivalent ytterbium present in the metal). The observed paramagnetism of cerium at room temperature corresponds to about 20% Ce4+ and 80% Ce3+, that of praseodymium and that of neodymium to about 10% of the quadripositive ion in each case, and that of samarium to about 20% of the bipositive ion in equilibrium with the tripositive ion. 

M Since the discovery of the magnetic properties of the cobalt alloy, samarium has been the "superstar" of the lanthanides. Music fans have their ears covered with samarium in the form of modem earphones... 

Among the rare-earths, samarium is the most commonly used because it provides the best permanent-magnet property. Other rare-earth elements are sometimes employed in combination with samarium to meet special requirements. The compounds SmCos and Sm2Coi7 are the most important magnetic materials among the cobalt-lanthanide alloys. 

Fomina, LG, Kiskin, M.A., Martynov, A.G, Aleksandrov, GG, Dobrokhotova, Z.V., Gorbimova, Y.G et al. (2004) Lanthanum(III), samarium(III), europium(lll), and thuUum(lll) binuclear acetates and pivalates synthesis, structure, magnetic properties, and solid-phase thermolysis. Zhurrml NeorganJcheskoi Khimii, 49 (9), 1463-1474. 

At the end of the 1960s, a new material with exceptional hard magnetic properties (Table 6.7) was prepared samarium-cobalt, SmCoj. Its most outstanding property is its magnetocrystalline anisotropy reported values are in the range (11-20) x 10 J/m (by comparison, Ba ferrite has an anisotropy of 0.33 x 10 J/m, Table 4.15). Rather than being a serendipitous discovery, the successful synthesis of SmCoj was the result of a systematic effort (Strnat, 1988). 

Compared to the rest of the periodic table, the lanthanide elements are less commonly used in research and industry because they are difficult to work with and extract. And for these reasons they are often far more expensive too. Many of the properties of the materials that they are made with can be made with cheaper alternatives. However, there are some specialist applications for the Ln elements. For example, the element neodymium is used in lasers and commercial magnets with very strong magnetic fields, and samarium is used for its magnetic properties. 

Spedding s group at Ames also showed that the rare earths had interesting magnetic properties when the temperature was lowered. As a result, many scientists worked with these metals and learned a great deal about the nature of magnetism. Today the best permanent magnets are made with neodymium or samarium metals as one of the constituents in an alloy. 

McColm and Thompson (1972) have characterized the rare earth cyanides by means of chemical analysis, IR spectrometry, and X-ray diffractometry and have measured their magnetic properties. The results indicate mixed products for Sm, Eu, and Yb (table 30), and the initial precipitate in the case of Eu and Yb contains a high percentage of bicyanide. Although the samarium product has been analyzed as Sm(CN)2, all physical measurements indicate that it is Sm(CN)j, which suggests that Sm(CN)2 is very unstable to disproportionation. They suggested that the X-ray lines of Ce(CN)3 and Sm(CN)3 could be explained in terms of... 

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. 

The compounds Ln(C5H5)2Cl also have been made only with the lanthanides above samarium (772). These compounds are stable in the absence of air and moisture, sublime near 200 °C, are insoluble in non-polar solvents, and exhibit room temperature magnetic moments near the free ion values (772, 113). The chloride ion may be replaced by a variety of anions including methoxide, phenoxide, amide and carboxylate. Some of these derivatives are considerably more air-stable than the chloride — the phenoxide is reported to be stable for days in dry air. Despite their apparent stability, little is known about the physical properties of these materials. The methyl-substituted cyclopentadiene complexes are much more soluble in non-polar solvents than the unsubstituted species. Ebulliometric measurements on the bis(methylcyclopentadienyl)lanthanide(III) chlorides indicated the complexes are dimeric in non-coordinating solvents (772). A structmre analysis of the ytterbium member of this series has been completed (714). The crystal and molecular parameters of this and related complexes are compared in Table 5. 

Permanent magnets having properties several times superior to any other known materials were developed in 1967. Praseodymium, yttrium, samarium, lanthanum, and cerium are alloyed with cobalt in the range... 

One of the most important uses of samarium is in the manufacture of very powerful magnets. Samarium is combined with the metal cobalt to make samarium-cobalt, or SmCo, magnets. They are among the strongest magnets known. They also have other desirable properties. For example, they can be used at high temperatures and do not react easily with substances around them. SmCo magnets are widely used in motors, such as those used to power specialized kinds of airplanes. 

Four binuclear samarium complexes [Sm( x-p-XOBz)2(Tp)]2 have been prepared by the reaction of SmCl3, K(Tp), and sodium p-X-benzoate (X = H, Cl, F, NO2) in 1 1 2 ratio. These complexes have been characterized by elemental analysis, IR spectroscopy, thermogravimetry, optical properties, X-ray, and magnetic measurement studies. The X-ray structure shows that these complexes are isostruc-tural, each samarium being seven-coordinate.627... 

---