Temperature-dependent vacuum tunneling spectroscopy of rare-earth manganates showing colossalmagnetoresistance and charge ordering

Abstract

We report here the results of vacuum tunneling spectroscopy of race-earth manganates which show colossal magnetoresistance (CMR) and charge ordering (CO). Three samples with different hole concentrations and average A site cation radii have been studied. A charge-ordering gap (Delta(CO)) opens up in the density of states (DOS) near EF, below the charge-ordering transition. A gap comparable to the transport gap opens up in the paramagnetic state also. There is an absence of gap only in the ferromagnetic metallic state. We have measured the temperature dependence of these quantities.