Density of states of hole-doped manganites: A scanning-tunneling-microscopy/spectroscopy study

Biswas, Amlan and Elizabeth, Suja and Raychaudhuri, AK and Bhat, HL (1999) Density of states of hole-doped manganites: A scanning-tunneling-microscopy/spectroscopy study. In: Physical Review B, 59 (8). pp. 5368-5376.

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Abstract

Variable temperature scanning-tunneling-microscopy/ spectroscopy studies on single crystals and epitaxial thin films of hole-doped manganites, which show colossal magnetoresistance, have been done. We have investigated the variation of the density of states (DOS), at and near the Fermi energy (E-f), as a function of temperature. Simple calculations have been carried out, to find out the effect of temperature on the tunneling spectra and extract the variation of density of states with temperature, from the observed data. We also report here atomic resolution images, on the single crystals and larger range images showing the growth patterns on thin films. Our investigation shows unambiguously that there is a rapid variation in density of states for temperatures near the Curie temperature (T-c). While for temperatures below T-c, a finite DOS is observed at E-f for temperatures near T-c a hard gap opens up in the density of states near E-f. For temperatures much higher than T-c, this gap most likely gives way to a soft gap. The observed hard gap for temperatures near T-c is somewhat higher than the transport gap for all the materials. For different materials, we find that the magnitude of the hard gap decreases as the T-c of the material increases and eventually, for materials with a T-c close to 400 K, the value of the gap approaches zero.

Item Type:	Journal Article
Publication:	Physical Review B
Publisher:	American Physical Society
Additional Information:	Copyright of this article belongs to American Physical Society.
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	06 Mar 2009 07:17
Last Modified:	19 Sep 2010 05:01
URI:	http://eprints.iisc.ac.in/id/eprint/18322

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