  The temperature (T) dependent x-ray diffraction (XRD) and resistivity
measurements of La0.175Pr0.45Ca0.375MnO3 (LPCMO) have been performed down to 2K
to understand the structural and transport properties. From room temperature
down to 220K, LPCMO exists in orthorhombic phase with Pnma structure and at
220K, it transforms to charge ordered (CO) monoclinic phase with P21/m
structure and remains as it is down to 2K. The CO phase is evident from the
occurrence of weak but well defined superlattice peaks in the XRD pattern. This
structural transformation is of first order in nature as evident from the phase
coexistence across the transition region. These results thus clearly illustrate
that LPCMO undergoes a first order structural phase transition from charge
disordered orthorhombic phase to CO monoclinic phase at 220K, consistent with
temperature dependent resistivity results. Our structural analysis of T
dependent XRD data using Rietveld refinement infers that below 220K, LPCMO
forms commensurate CO monoclinic P21/m structure with four times structural
modulation.
