Ferromagnetic pyrochlores

Oxide pyrochlores of the general formula A2B2O7 show interesting electronic properties (Subramanian et al, 1983). Ferromagnetic pyrochlores of rare earths have also been described (Subramanian et al., 1988). A composition-dependent metal-semiconductor transition has been found in A2(Ru2 (AJ07 j, where A = Bi or Pb (Beyerlein et al., 1988). 

The only R2V2O7 pyrochlores reported are for R = Tm, Yb and Lu (Shin-ike et al. 1977). These three compounds are ferromagnetic, as indicated in table 6. In addition, magnetic properties have been investigated in the solid solutions Lu2-,cY,cV2 07, Lu2- Sc V207, and R2V2 j,Mo,j07 (table 6). 

Pyrochlores of the type A2Mn2 07 are known for Dy, Ho, Eu, Tm, Yb, Lu, Y, Sc, In and T1 (Subramanian et al. 1988). All exhibit ferromagnetic behavior (table 6). On the other hand, there are indications that these compounds do not possess a spontaneous moment in the absence of an applied field. 

Ferromagnetism has also been reported for pyrochlores of the type R2Cr3 + Sb= + 07 (table 6). 

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