Signature of phase coexistence in electron doped manganite

Abstract

We investigate the temperature evolution of the electronic structure of La_0.2Sr_0.8MnO₃ using Mn K-edge extended x-ray absorption fine structure (EXAFS) and state-of-the-art high resolution photoemission spectroscopy. This compound undergoes a transition from cubic paramagnetic metal to tetragonal C-type antiferromagnetic insulator around 265 K (T_N). EXAFS results exhibit a direct link between the temperature induced change in resistivity and the structural parameters of the MnO₆ octahedra. The high resolution photoemission spectra reveal a gradual evolution of the spectral function exhibiting a pseudo gap at 300 K to a hard gap around 205 K. The appearance of hard gap much below the transition temperature suggests coexistence of two phases in the vicinity of the phase transition temperature, which might be important in the understanding of phase separation scenario widely discussed in this class of materials.