Intermetallic Mossbauer effect

In the second chapter (94) of the present volume, Dormann reviews the advances that have been made in NMR spectroscopy over the past 12 years, since Barnes overview on NMR, EPR and Mossbauer effect, in volume 2 of the HANDBOOK. Dormann s contribution is more specialized since it concentrates on NMR in inter-metallic, magnetically ordered compounds. As Dormann points out, considerable progress has been made in experimental techniques which enable experimentalists to study materials and perform measurements that could not have been done ten years ago, and this has led to a much better understanding and comprehension of these magnetic lanthanide materials. These experimental advances allow the determination of the temperature dependence of spontaneous magnetization, direction of easy magnetization, and the electronic structure of intermetallic compounds with non-magnetic components. 

I = 7/2-1—> 5/2-F). The materials that can be studied, thanks to the Mossbauer effect of the above-mentioned nuclei, are also varied. Both cathode and anode materials can be examined. Moreover, the electrochemical reactions in which they are involved may vary from intercalation to conversion and/or alloying. Table 28.1 shows some examples. Fe MS provides useful information in the study of insertion cathodes, such as olivine LiFeP04, as well as layered solids structurally related to LiCo02. Fe MS is also useful to analyze anodes consisting of binary or ternary oxides for conversion reactions, or tin intermetallics that react with lithium by alloying processes. In the latter case, a multiisotope approach can be developed, due to the Mossbauer effect of both Fe and Sn nuclei. 

Mossbauer effect methods have received wide application to the study of intermetallic compounds. This subject was first reviewed by Nowik (1966) and more recently by Taylor (1971) and also Wallace (1973) as part of general reviews of the properties of lanthanide intermetallics. Many examples are also included in the NGR review by Ofer et al. (1%8) as well as in the text by Greenwood and Gibb (1971). 

Magnetically ordered intermetallic compounds of the rare earths with iron and tin have been the subject of numerous investigations, reflecting the relative ease of carrying out Mossbauer effect measurements with these two convenient nuclei ( Fe and " Sn). A variety of pseudo-binary systems may also be formed (e.g., R(FeiCoi i)2) in which the iron or tin may be diluted without altering the crystal structure. 

Sor] Sorescu, M., Pourarian, R, Brand, Mossbauer Study of Hydrohenation Effect in Iron Rich Intermetallics , J. Mater. Sci. Lett., 22(22), 1569-1572 (2003) (Crys. Stracture, Experimental, 8)... 

In this chapter, using samples of mainly three types of magnetic materials, namely, nanosized powders of ferrites, mechanically alloyed/milled Fe-Cr-AI intermetallics, and a Fe-AI multilayer system, it has been demonstrated how Mossbauer spectroscopy is a powerful tool to understand the bulk magnetic properties in such nanosized systems. This is mainly because of the extreme sensitivity of the Mossbauer probe atom to short-range effects that get modified on a... 

It was stated in the preceding section that 2 is a suitable choice of effective absorber thickness. Table 4 presents the needed area density of the lanthanide (in natural isotopic abundance) or the actinide for different measuring temperatures and various Debye temperatures. For intermetallic compounds 0 200 K is a good guess. A typical Mossbauer absorber covers an area of 2-4 cm. For most cases about 0.5 g of material suffices. As said before, powder samples are fine, single crystals are not necessary. 

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