INFRARED-SPECTRA AND NORMAL VIBRATIONS OF (LA,ND)BACACU3O7

The Fourier transform infrared spectra have been recorded for the seri es of (La,Nd)BaCaCu3O7-y at 300 and 85 K. These compounds are isostruc tural to YBa2CU3O7-y and belong to the space group Pmmm: (D-2h(1)) Of orthorhombic crystal system with 39 lattice vibrations distributed amo ng the various species of the group; The spectra of the entire series have been discussed and utilized to conclude the final vibrational ana lysis. A normal coordinate analysis has been done for LaBaCaCu3O7 by f itting the observed IR values at zero wavevector. The strong bands are assigned to A(g) and B-1u, which are vibrations along the c direction , The bands which are assigned to B-2g, B-3g, B-2u and B-3u vibrations in the ab plane are weak because of the screening effect from free ch arge carriers in the plane. The computation results in the values of f orce constants and eigenvectors giving complete description of the lat tice vibrations of (La,Nd)BaCaCu3O7.