CHARGE-TRANSFER AND PHONONS IN MISFIT LAYER COMPOUNDS (RS)(X)NBS2 (R EQUALS RARE-EARTH X-APPROXIMATE-TO-1.2)

Misfit layer compounds (RS)(x)NbS2 (R = rare earth; x approximate to 1 .2) are made of two types of layers: RS and NbS2. Polarized Raman spec tra have been measured on (RS)(x)NbS2 (R = La, Ce, Pr, Nd, Sm, Dy, Yb) in order to study the interlayer interaction between the RS and the N bS2 layers and the effect of the charge transfer from the RS layer to the NbS2 layer, The behavior of the intralayer E mode of the NbS2 laye r in (RS)(x)NbS2 is sensitive to the charge transfer and shifts consid erably to higher frequency compared with that of the pristine compound 2H-NbS2. Two Raman bands whose peak frequencies depend on the mass of the R atoms appear below 200 cm(-1). These bands are attributed to th e mode relevant to the RS layer.