Magnetic properties rare earth elements

Owing to peculiar physical and chemical properties, rare-earth elements are used in various materials and consumer products, and thus, have become indispensable for our modem life. The world-wide rare-earth oxide consumption by the market sector in 2008 (Goonan, 2011) shown in Fig. 1 indicates that rare earths are used in glass industry, catalysts, neodymium magnets, battery alloys and other metallurgical additives, phosphors, ceramics, and other. According to the world mine production of rare earth in 2009 (Cordier, 2011),... 

The morning session was devoted to a general explanation of the areas of application in studying magnetic properties, oxidation states, compounds, and metal structure. In the afternoon, reviews of the Mossbauer investigations of iron, tin, iodine, tellurium, and some of the rare earth elements were presented. The meeting concluded with a discussion on the future of Mossbauer Spectroscopy in which an interested audience participated. 

In order to bring about a systemization among the variety of uses I have broken down the ises of the rare earth elements into five groups of properties chemical, metallurgical, optical, magnetic and nuclear. 

Magnetic Properties. The rare earth elements show as a result of their atonic stixicture interesting magnetic prope2 ies which have led to various applications. 

In general, hcwever, one can say that vhere the optical properties, the chemical properties and the magnetic properties are used, substitution is not to be feared, vhile in the use of metallurgical and nuclear properties there is always the danger that a more economic solution of the problem can squeeze out the rare earth elements. 

The properties of some rare-earth binary alloys with platinum group metals are also important in view of the role they can play in the chain of preparing ternary hydrides. Many of the alloys of the series R-M, where R is a rare earth element and M is a Group VIIIB metal, have been investigated structurally and magnetically. The alloys with iridium all have cubic structures, whereas those... 

Boron has a particular affinity with rare earth elements, and forms rare earth borides which are of particular interest. The rare earth atoms supply electrons to the boron atomic framework to stabilize and form novel structures, while the shell of f electrons supplies further attractive properties like magnetism. Borides with lower boron content, like the hexaborides RB6 and tetraborides RB4 are well known metallic compounds and have been studied throughout the years, revealing interesting magnetic properties (e.g. Gignoux and Schmitt, 1997). 

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 fact that Tc is essentially unchanged by replacement of Y with the magnetic rare earth elements points to the Cu-O sublattice as the source of the superconducting properties of Y,Ba2Cu309 y. Mixtures of rare earths or alkaline earths (2,13) also do not affect Tc, again emphasizing the key role of the Cu-O sublattice. 

Fig. 2. The rare-earth elements now used in rare earth-cobalt permanent magnets, their effect on magnet properties (referenced to Sm alloy), and relative cost of the rare earth component.

The bond energies Qhk, Qck, and Qok proved to belong to periodic functions Qhk are observed to change parallel to the effective magnetic moment /a. In the latter, the periodic properties of rare earth elements are known to be manifested especially distinctly. For Qhk this parallelism is seen in Fig. 52 in which the values Qhk from Table XII... 

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