Tunneling Study of the Charge-Ordering Gap on the Surface of La${}_{0.350}$Pr${}_{0.275}$Ca${}_{0.375}$MnO${}_3$ Thin Films

Abstract

Variable temperature scanning tunneling microscopy/spectroscopy studies on (110) oriented epitaxial thin films of La${}_{0.350}$Pr${}_{0.275}$Ca${}_{0.375}$MnO${}_3$ are reported in the temperature range of 77 to 340 K. The films, grown on lattice matched NdGaO${}_3$ substrates, show a hysteretic metal-insulator transition in resistivity at 170 K. The topographic STM images show step-terrace morphology while the conductance images display a nearly homogeneous surface. The normalized conductance spectra at low temperatures (T$<$150 K) show an energy gap of 0.5 eV while for T$\ge$180 K a gap of 0.16 eV is found from the activated behavior of the zero bias conductance. The presence of energy gap and the absence of phase separation on the surface over more than 2 $\mu$m$\times$2 $\mu$m area contradicts the metallic behavior seen in resistivity measurements at low temperatures. We discuss the measured energy gap in terms of the stabilization of the insulating CO phase at the film surface.

5 pages, 5 figures To appear in Phys. Rev. B

References in corpus (1)

• Scaled frequency-dependent transport in the mesoscopically phase-separated colossal magnetoresistive manganite La_{0.625-y}Pr_yCa_{0.375}MnO_3

Cited by in corpus (1)

• Study of Short-distance Spin and Charge Correlations and Local Density-of-States in the CMR regime of the One-Orbital Model for Manganites