  This paper reports infrared spectroscopic studies on GdBaCo$_{2}$O$_{5.5}$
layered perovskite which exhibits successive magnetic transitions from
paramagnetic to ferromagnetic to antiferromagnetic states as well as high
temperature metal to insulator transition and a change in charge transport
mechanism at low temperature. Infrared absorption spectra recorded at various
temperatures in the range 80 K to 350 K reveal changes in the positions of Co-O
stretching and bending frequencies which provide an explanation to the magnetic
and transport behaviour of this compound.
