Itinerant electron ferromagnets

Electronic phase separation in rare-earth cobaltates of the type Lnj-jAj-CoOs has come to the fore in the last 2 years. La0 5Sr0 5Co03 and other members of this family were once considered to be itinerant electron ferromagnets... 

Rao, C. N. R, Parkash, O., Bahadur, D., Ganguly, P. Nagabhushana, S. 1977 Itinerant electron ferromagnetism in SR2 + -doped rare-earth, CA2 +-doped rare-earth, and BA2+-doped rare-earth orthocobaltites (LN[ 3 + )M 2 + )Co03). J. Solid State Chem. 22, 353-360. (doi 10.1016/ 0022-4596(77)90011-1)... 

M. N. Shah and G. Vitiello, Self-consistent formulation of itinerant Electron Ferromagnet, Nuovo Cimento 30B, 21-42 (1975). 

Originally the formula obtained for purely itinerant electron ferromagnets was used to explain the dependence of dTc/dP on Tc in the lanthanide-3dTM compounds ... 

Zener appears to have been the first to consider this problem to some depth in his theoretical work on ferromagnetic crystals of the type l.a. Ca.MnO, (Zener 1951). For x = 0 one has LainMnin03 but for x > 0 some of the Mn will be 4+, and so we have the structure I. a " / a " Mn "(Mn CL in which some Mn-Mn pairs will be mixed valence, that is, MiF Mnj) or MnJ) Mn . Mnm is 3d4 (S = 2) and MnIV is 3d3 (S = 3/2), and Zener proposed that the excess electron (also called itinerant electron or Zener electron) on Mn111 can travel to the MnIV via a doubly-occupied p-orbital of... 

The reduced orbital overlap between the radicals reduces the bandwidth and the electronic structures could be better considered as those of a localised rather than itinerant electron system. This poor overlap results in very small antiferromagnetic interactions being observed, and the compounds behave as nearly perfect Curie-Weiss paramagnets. In the cases when improved lateral interactions between the stacks are achieved by change of the substituents85 the compounds behave as weak ID ferromagnets due to the effective orthogonality of the S C interactions. 

Fig. 2 Representation of the ferromagnetic alignment of d localized spins resulting from the interaction with itinerant electrons through short intermolecular contacts...

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