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Title: Electronic transport and conduction mechanism transition in La{sub 1∕3}Sr{sub 2∕3}FeO{sub 3} thin films

Abstract

We report on the electronic transport properties of epitaxial La{sub 1∕3}Sr{sub 2∕3}FeO{sub 3} films using temperature dependent resistivity, Hall effect, and magnetoresistance measurements. We show that the electronic phase transition, which occurs near 190 K, results in a change in conduction mechanism from nonadiabatic polaron transport at high temperatures to resistivity behavior following a power law temperature dependence at low temperatures. The phase transition is also accompanied by an abrupt increase in apparent mobility and Hall coefficient below the critical temperature (T*). We argue that the exotic low temperature transport properties are a consequence of the unusually long-range periodicity of the antiferromagnetic ordering, which also couples to the electronic transport in the form of a negative magnetoresistance below T* and a sign reversal of the Hall coefficient at T*. By comparing films of differing thicknesses, stoichiometry, and strain states, we demonstrate that the observed conduction behavior is a robust feature of La{sub 1∕3}Sr{sub 2∕3}FeO{sub 3}.

Authors:
; ; ; ;  [1]
  1. Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States)
Publication Date:
OSTI Identifier:
22303999
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 23; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANTIFERROMAGNETISM; CARRIER MOBILITY; CRITICAL TEMPERATURE; ELECTRIC CONDUCTIVITY; EPITAXY; FERRITES; HALL EFFECT; LANTHANUM COMPOUNDS; MAGNETORESISTANCE; PERIODICITY; PHASE TRANSFORMATIONS; STOICHIOMETRY; STRAINS; STRONTIUM COMPOUNDS; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0400-1000 K; THICKNESS; THIN FILMS

Citation Formats

Devlin, R. C., Krick, A. L., Sichel-Tissot, R. J., Xie, Y. J., and May, S. J., E-mail: smay@coe.drexel.edu. Electronic transport and conduction mechanism transition in La{sub 1∕3}Sr{sub 2∕3}FeO{sub 3} thin films. United States: N. p., 2014. Web. doi:10.1063/1.4883541.
Devlin, R. C., Krick, A. L., Sichel-Tissot, R. J., Xie, Y. J., & May, S. J., E-mail: smay@coe.drexel.edu. Electronic transport and conduction mechanism transition in La{sub 1∕3}Sr{sub 2∕3}FeO{sub 3} thin films. United States. doi:10.1063/1.4883541.
Devlin, R. C., Krick, A. L., Sichel-Tissot, R. J., Xie, Y. J., and May, S. J., E-mail: smay@coe.drexel.edu. Sat . "Electronic transport and conduction mechanism transition in La{sub 1∕3}Sr{sub 2∕3}FeO{sub 3} thin films". United States. doi:10.1063/1.4883541.
@article{osti_22303999,
title = {Electronic transport and conduction mechanism transition in La{sub 1∕3}Sr{sub 2∕3}FeO{sub 3} thin films},
author = {Devlin, R. C. and Krick, A. L. and Sichel-Tissot, R. J. and Xie, Y. J. and May, S. J., E-mail: smay@coe.drexel.edu},
abstractNote = {We report on the electronic transport properties of epitaxial La{sub 1∕3}Sr{sub 2∕3}FeO{sub 3} films using temperature dependent resistivity, Hall effect, and magnetoresistance measurements. We show that the electronic phase transition, which occurs near 190 K, results in a change in conduction mechanism from nonadiabatic polaron transport at high temperatures to resistivity behavior following a power law temperature dependence at low temperatures. The phase transition is also accompanied by an abrupt increase in apparent mobility and Hall coefficient below the critical temperature (T*). We argue that the exotic low temperature transport properties are a consequence of the unusually long-range periodicity of the antiferromagnetic ordering, which also couples to the electronic transport in the form of a negative magnetoresistance below T* and a sign reversal of the Hall coefficient at T*. By comparing films of differing thicknesses, stoichiometry, and strain states, we demonstrate that the observed conduction behavior is a robust feature of La{sub 1∕3}Sr{sub 2∕3}FeO{sub 3}.},
doi = {10.1063/1.4883541},
journal = {Journal of Applied Physics},
number = 23,
volume = 115,
place = {United States},
year = {Sat Jun 21 00:00:00 EDT 2014},
month = {Sat Jun 21 00:00:00 EDT 2014}
}
  • Synchrotron x-ray diffraction and electrical resistivity were used to probe the electronic phase transition in two strained La{sub 1/3}Sr{sub 2/3}FeO{sub 3} films on (001) SrTiO{sub 3} substrates, one nominally stoichiometric and one with a higher concentration of oxygen vacancies. We present evidence that oxygen vacancies inhibit the size of charge ordered domains and reduce the abruptness of the phase transition. Additionally, the correlation lengths measured from (4/3 4/3 4/3) peaks, arising from charge disproportionation, increase rapidly across the transition, suggesting that the resistivity increase at the transition temperature is caused by the nucleation and growth of charge ordered domains.
  • 3d metal K-shell X-ray absorption spectra of perovskites with the composition La{sub 1-x}Ca{sub x}CoO{sub 3-{delta}} (x=0, 0.2, 0.4, 0.5, 0.6, 0.8), La{sub 1-x}Sr{sub x}CoO{sub 3-{delta}} (x=0, 0.1, 0.2, 0.3, 0.4, 0.5) and La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}} (x=0, 0.2, 0.4, 0.5, 0.6, 0.8) are compared on the basis of pre-edges, white line features and extended fine structures. The measurements were performed at 300 K and for La{sub 1-x}Ca{sub x}CoO{sub 3-{delta}} also at temperatures as low as 10-20 K. Going to low-temperature the measurements indicate an increase in t{sub 2g}{sup Low-Asterisk} and a decrease in e{sub g}{sup Low-Asterisk} orbital occupancy, which ismore » most accentuated in the LaCoO{sub 3} sample. Virtually no Co K-edge shift was observed for the La{sub 1-x}Ca{sub x}CoO{sub 3-{delta}} and La{sub 1-x}Sr{sub x}CoO{sub 3-{delta}} compounds and the Co-O distances are also not significantly reduced when La{sup 3+} is partially substituted by Ca{sup 2+} or Sr{sup 2+}. From the pre-edge features of these perovskites we are tended to conclude that the t{sub 2g}{sup Low-Asterisk} orbitals are less, and the e{sub g}{sup Low-Asterisk} orbitals are more occupied with increasing x in the Ca and Sr substituted compounds, whereas the total d-electron density is not changing. These results indicate that cobalt prefers a valence state of 3{sup +} in these Co perovskites. This could also be confirmed with iodometric titrations. The Fe perovskites behave differently. In contrast to the Co perovskites, for La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}} perovskites the Fe K-edge is shifted, the pre-edge features intensity is increasing and the Fe-O bond length is decreasing with increasing x. The valence states of the iron in the La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}} perovskites in fact increase as much as x increases. - Graphical abstract: Co K and Fe K pre-edge of La{sub 1-x}Ca{sub x}CoO{sub 3-{delta}} and La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}} perovskites one of the evidences in favor of {delta}=x/2 for the Co-perovskites and {delta}=0 for the Fe-perovskites. Highlights: Black-Right-Pointing-Pointer XAS a valuable tool to evaluate the valence states of Co and Fe perovskites. Black-Right-Pointing-Pointer For La{sub 1-x}Ca{sub x}CoO{sub 3-{delta}} and La{sub 1-x}Sr{sub x}CoO{sub 3-{delta}} perovskites {delta} is close to x/2. Black-Right-Pointing-Pointer For La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}} series {delta} is close to 0. Black-Right-Pointing-Pointer Discussion of the x dependency of the pre-edge bands.« less
  • Ordered electronic phases are intimately related to emerging phenomena such as high Tc superconductivity and colossal magnetoresistance. The coupling of electronic charge with other degrees of freedom such as lattice and spin are of central interest in correlated systems. Their correlations have been intensively studied from femtosecond to picosecond time scales, while the dynamics of ordered electronic phases beyond nanoseconds are usually assumed to follow a trivia thermally driven recovery. Here, we report an unusual slowing down of electronic phases across a first-order phase transition, far beyond thermal relaxation time. Following optical excitation, the recovery time of both transient opticalmore » reflectivity and x-ray diffraction intensity from a charge-ordered superstructure in a La 1/3Sr 2/3FeO 3 thin film increases by orders of magnitude longer than the independently measured lattice cooling time when the sample temperature approaches the phase transition temperature. The combined experimental and theoretical investigations show that the slowing down of electronic recovery corresponds to the pseudo-critical dynamics that originates from magnetic interactions close to a weakly first-order phase transition. As a result, this extraordinary long electronic recovery time exemplifies an interplay of ordered electronic phases with magnetism beyond thermal processes in correlated systems.« less
  • The electronic phase diagram of epitaxial La{sub 1−x}Sr{sub x}FeO{sub 3} films is presented. The films were grown on SrTiO{sub 3} using molecular beam epitaxy with post-growth annealing to minimize oxygen vacancies. Insulating behavior is observed from x = 0–0.9, with metallic conduction only present for x = 1.0. While the La-rich compounds exhibit polaron conduction over all temperatures measured, the Sr-rich films exhibit an electronic phase transition within the compositional window of x = 0.49–0.9 as revealed by temperature-dependent resistivity measurements. The transition temperatures are found to decrease with increasing Sr content. The constructed phase diagram is discussed in the context of other 3d e{sub g}more » perovskite systems including manganites and cobaltites.« less