Direct measurement of the charge ordering gap in using vacuum tunnelling

We have used tunnelling spectroscopy (TS) to probe the density of states (DOS) of the rare earth manganate , which shows a transition to a charge ordered (CO) antiferromagnetic insulating state from a ferromagnetic metallic state. We find that a gap opens up in the DOS around the Fermi level, , as the solid is cooled below the charge ordering temperature . The charge ordering gap was found to be strongly temperature dependent for and for it reaches a limiting value of nearly 0.27 eV. Above the temperature dependence of the DOS at was found to be similar to that of the solids such as which show colossal magnetoresistance but no charge ordering.