Temperature-Dependent Pseudogaps in Colossal Magnetoresistive Oxides

Direct electronic structure measurements of a variety of the colossal magnetoresistive oxides show the presence of a pseudogap at the Fermi energy E_F which drastically suppresses the electron spectral function at E_F. The pseudogap is a strong function of the layer number of the samples (sample dimensionality) and is strongly temperature dependent, with the changes beginning at the ferromagnetic transition temperature T_c. These trends are consistent with the major transport trends of the CMR oxides, implying a direct relationship between the pseudogap and transport, including the "colossal" conductivity changes which occur across T_c. The k-dependence of the temperature-dependent effects indicate that the pseudogap observed in these compounds is not due to the extrinsic effects proposed by Joynt.