Light lanthanides, magnetic properties

The light lanthanides also exhibit some unusual electrical and magnetic properties. The superconductivity of lanthanum has already been mentioned. But when its behavior is compared to the superconductivity in scandium, yttrium and lutetium, we find lanthanum is unusual. The ordering temperature T, and pressure dependence of T are both larger in lanthanum than in the other three superconductors (see section 3.7.3 and fig. 12a). 

TABLE 9 The magnetic properties of the light lanthanides.The magnetic moments are all ... 

A fairly recent review of the physical properties of a large number of the rare earth intermetallic compounds may be found in the article by Taylor (1971) (also see chs. 9, 11, 13, 14, 15 and 18). A comprehensive review of the magnetic properties of such compounds has also been given by Wallace (1971) and Kirchmayr and Poldy (ch. 14). The reader may also refer to the review article by Bertaut (1972). As discussed in section 2.6, the basic physics involved in the magnetism of these materials involves the interplay between comparable exchange and crystal field effects, as in the light lanthanide metals, with possible additional complications resulting from interactions with lattice phonons. 

Apart from d- and 4f-based magnetic systems, the physical properties of actinides can be classified to be intermediate between the lanthanides and d-electron metals. 5f-electron states form bands whose width lies in between those of d- and 4f-electron states. On the other hand, the spin-orbit interaction increases as a function of atomic number and is the largest for actinides. Therefore, one can see direct similarity between the light actinides, up to plutonium, and the transition metals on one side, and the heavy actinides and 4f elements on the other side. In general, the presence or absence of magnetic order in actinides depends on the shortest distance between 5f atoms (Hill limit). 

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