Magnetic order lanthanide elements

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). 

The i Fe2 materials in crystalline form possess very large magnetic-elastic interactions even at room temperature (Clark, 1974) (see also ch. 15, sections 1 and 2). Clark (1974) has shown that the 0 K lanthanide magnetoelastic coupling coefficients are of the same order of magnitude in the RFe2 compounds as in the lanthanide elements despite the overall cubic symmetry of the compounds. In the amorphous state, as expected, bulk magnetostrictions are smaller than in the... 

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