A LANTHANIDE LANTHOLOGY (.pdf) - Davidson Physics

SAMARIUMSamarium metal is made directly from the oxide by reaction with, for example, lanthanum;vaporization of the volatile Sm drives the reaction to completion. The room-temperature structureof the metal is unusually complex, due to involvement of the f-orbitals in the bonding.Introduction of the intermetallics SmCo 5 and Sm 2 Co 17 , as permanent magnet materials [1]created a significant market for samarium. These Sm-Co compounds are made by areduction-diffusion process whereby Sm 2 O 3 is converted directly to the Sm-transition metal alloy,Sm-metal is not isolated; see metals.The magnetic strength of the Sm-Co compounds arises predominantly from the cobalt atomsbut the role of Sm is crucial in determining that property. In essence Sm helps define an anisotropicstructure "locking" the cobalt moments in place and making demagnetization impossible.Although now over-shadowed by the Nd-Fe-Bmaterials, a market niche remains for thehigh-temperature-stable (Curie temperature ≥ 700 °C)Sm-based magnet alloys, particularly in microwaveapplications. A recently discovered ternary Smtransitionmetal system, Sm 2 -Fe l7 -N ≈3 , also offerspotential as a permanent magnet material[2].The chemical behavior in aqueous systemsof Samarium is intermediate between that of Yttriumand Neodymium. Nevertheless, the moderate stability -albeit less than Eu(II) - of Sm(II) differentiatesSamarium from most other Ln's. The iodide, SmI 2 [3],in THF is a stable versatile reagent in synthetic organicchemistry where its oxophilic nature makes possible awide variety of organic-molecule transSmElementAtomic Number 62Atomic Weight 150.4Electron[Xe]4f 6 6s 2configurationValency 3 (2)Potential E M(III)/M(II -1.55 VIonic radius for 8- 108 pmcoordinationMagnetic moment 0.85 µBmetalCrystal Structure ComplexMelting Point 1074 °CBoiling Point 1794 °CDensity7.52 g/cm3Metallic Radius 180 pm[1] Permanent Magnets, J.J.Becker, Scientific American, 1970(December), 92 : RETM 5 and RE 2TM 17Permanent Magnets Development, K.Kumar, J.Appl.Phys., 1988, 63(6), R13[2] Intrinsic Magnetic Properties of New Rare-Earth Iron Intermetallic Series, J.M.D.Coey et al.,J.Mag.Magnetic Mat., 1991, 101, 310[3] SmI 2: A Most Useful Material, S-H. Wang, Rev. Inorg. Chem., 1990, 11, 137