Study of x-ray photo-emission spectroscopy and multiple metal to insulator transitions in an electron doped system of La1-xZrxMnO3 (x = 0.10, 0.20)

Abstract

In this study, we have investigated the crystallographic structure and the temperature-dependent resistivity of an electron doped La1-xZrxMnO3 manganite system. X-ray photoemission spectroscopy (XPS) for core level study has been carried out to confirm the electron doping. The results of XPS core level study suggests that Zr ions are in the tetra-valent state and Mn ions are forced to be in a mixed state of Mn3+ and Mn2+. Rietveld refinement of X-ray powder diffraction results have confirmed the rhombohedral crystal symmetry of the samples with space group R-3c. The temperature dependent resistivity and magnetization plots exhibit insulator to metal transition (MIT) accompanied with Paramagnetic to Ferromagnetic transition (Tc). Three independent MIT transitions have been observed, the first sharp transition at TP1 showed a strong correlation with the magnetic transition Tc confirming that the intrinsic MIT happened at TP1. The insulating behaviour below T1 has been attributed to the competition between the short range orbital/charge order and the long range FM order. The transition at lower temperature TP2 may be attributed to the percolative transport of charge carriers through ferromagnetic metallic domains. The third upturn transition assigned as Tmin has been ascribed to combined effect of electron-electron and Kondo interactions, the detailed qualitative analysis and discussion of which is under preparation.