Lanthanide elements magnetic properties

Evidence other than that of ion-exchange favours the view of the new elements as an inner transition series. The magnetic properties of their ions are very similar to those of the lanthanides whatever range of oxidation states the actinides display, they always have -1-3 as one of them. Moreover, in the lanthanides, the element gado-... 

Lanthanides are coextracted with actinides and then separated from actinides, which are forecasted to be sent to a repository. The lanthanide elements comprise a unique series of metals in the periodic table. These metals are distinctive in terms of size, valence orbitals, electrophilicity, and magnetic and electronic properties, such that some members of the series are currently the best metals for certain applications. Increased use of the lanthanides in the future is likely, because their unusual combination of physical properties can be exploited to accomplish new types of chemical transformations. These elements coextracted with actinides and then separated from the latter, could in the future be recovered and used (among the lanthanides, only 151Sm is a long-lived isotope (half-life 90 years)).4... 

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. 

Lanthanide elements have atomic numbers ranging from 57 to 71. With the inclusion of scandium (Sc) and yttrium (Y), a total of 17 elements are referred to as the rare earth elements. A mixture of rare earths was discovered in 1794 by J. Gadolin and ytterbium was separated from this mixture in 1878 by Mariganac, while the last rare earth element promethium (Pm) was separated by a nuclear reaction in 1974. Therefore, a period of more than 100 years separates the discovery of all the rare earth elements. In the latter part of the last century scientists started to focus on the applications of rare earth elements. Numerous interesting and important properties were found with respect to their magnetic, optical, and electronic behavior. This is the reason that many countries list all rare earth elements, except promethium (Pm), as strategic materials. Rare earth coordination chemistry, therefore, developed quickly as a result of this increased activity. 

The magnetic properties of lanthanides are different than transition elements ... 

The transition metal ions generally have a number of d electrons in their outer shell, and because the energy difference between the various configurations is small, the arrangement adopted will depend upon a variety of external factors, such as the geometry of the crystal structure (see also Chapter 12 and Section S4.5). The lanthanides have an incomplete 4f shell of electrons, and the actinides an incomplete 5f shell. In these elements, the f orbitals are shielded from the effects of the surrounding crystal structure. The d and f electrons control many of the important optical and magnetic properties of solids. 

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. 

The varied magnetic properties of the elemental lanthanide metals have attracted researchers over decades. The continuously improving purity of the materials has led to a munber of revisions to the state of our understanding with time. A summary of the main crystallographic and magnetic parameters is presented in table 2. Details on bulk measurements can be foimd, for example, in Rhyne (1972) and McEwen (1978), neutron data in Koehler (1972) and Sinha (1978). A modem treatise on magnetic properties is given by Jensen and Mackintosh (1991). All metals contain the 3 ion except Eu and Yb which are 2. ... 

Many important conclusions of the calculations can be found in the original papers quoted. In the following sections, therefore, we will discuss a few interesting points concerning the effects of the third element on the magnetic properties of the lanthanide-transition-metal magnets. 

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