Ferromagnetism lanthanides

A deeper analysis [80] on this Cu - Dy chain showed that NN and NNN interactions are efficient above Tc and that inter spin-ladder ferromagnetic interaction is observed in this family of compounds [79-82]. Attempts were made to use the 3d tectons with other lanthanide precursors, such as hexanuclear lanthanide clusters. Regular chains were obtained with Dy-Cu ferromagnetic interaction but their close packing prevents observation of SCM behaviour [83]. 

For a very few metals, however, the unpaired electrons in the conduction band can lead to ferromagnetism. In the whole of the Periodic Table, only iron, cobalt, nickel, and a few of the lanthanides (Gd, Tb) possess this property. So, what is so special about these elements that confers this uniqueness on them It is not their crystal structure they each have different structures and the structures are similar to those of other non-ferromagnetic metals. Iron, cobalt, and nickel, however, all have a nearly full, narrow 3c/band. 

EUR.U4P12 is metallic and orders ferromagnetically for temperatures below 18 K (Grandjean et al., 1983 Sekine et al., 2000b). The saturation moment is about 10% smaller than the Eu+2 value of 7/u-b which could imply an intermediate Eu valence or an incomplete filling of the lanthanide site. The value of the Eu isomer shift in EURU4P12 is -9.3 mm/s, which is compatible with Eu+2 in a metallic compound. 

EuRu4Sbn is metallic and becomes ferromagnetic for temperatures below 3.3 K (Takeda and Ishikawa, 2000b). The low temperature saturation moment is about 6.2/xb, 89% of the Eu+2 value. Low temperature heat capacity measurements indicate that the magnetic entropy removed due to magnetic order is also only about 90% of its expected value (Rln8). It is likely that the lanthanide site is not completely filled in this compound although mixed valence behavior can not be ruled out with the available data. 

In what follows, the first section is devoted to describing transition-metal Pc complex-based ferromagnets and also other related complexes exhibiting no ferromagnetic order. The second section describes the magnetic interaction of n-radical phthalocyanines in crystals. In the last section, we present Pc-based SMMs and a general discussion on magnetism and electronic structure of lanthanide Pc complexes. 

Most, but not all, of the observed magnetic behavior of the lanthanide hydrides fits in with the notion that the hydrogen-saturated metal lacks conduction electrons. The hydride of europium is an exception EuH186, the highest hydride that has been formed in this laboratory, has been shown (15) to be ferromagnetic below 25° K. This would ordinarily imply the existence of electrons in the con-... 

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