Rare earth intercalation and magnetic properties of layer-type compounds

The rare earth metals Eu and Yb and the alkaline earth Sr have been intercalated in the groups IV and VI dichalcogenides with layer type structures. The intercalations were carried out at low temperatures in liquid ammonia solutions and were shown to be free of the ferromagnetic impurities Eu(NH2)2 and Eu(NH3)6. Lattice parameter increases in the c direction of the hexagonal cell, independent of the concentration of the intercalated species, from 18.39 A for pure 3R MoS2 to 27.84 for the Eu intercalated material were measured. We find the intercalated species to go between every layer and ammonia is intercalated along with the metals. The composition of MoS2 fully intercalated with Eu is MoS2(Eu).9−1.0(NH3)1−1.5. MoS2 orders ferromagnetically at 4–5°K when intercalated with Eu in concentrations greater than MoS2(Eu).5−.6. The ferromagnetic composition have paramagnetic Curie temperatures of 8–9°k and Curie constants consistent with the europium being all divalent, i.e., CM = 7.9. When Yb and Sr are interc...