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Article Dans Une Revue Journal of Superconductivity and Novel Magnetism Année : 2019

Resistivity of Manganite Thin Film Under Strain

Résumé

A complex study of the electron transport and magnetic characteristics of epitaxial manganite films La0.7Ba0.3MnO3 (LBMO) was carried out under conditions of the crystal structure tension caused by a mismatch between the parameters of the LBMO crystal and the substrate. The epitaxial thin films with the thickness 40-100 nm were grown by pulsed laser deposition at T = 700-800 °C in pure oxygen pressure 0.3-1 mbar. The substrates (110) NGO, (001) STO, (001) LAO, and (001) LSAT were used. By comparison of the lattice parameter of LBMO targets with substrate's one, the lattice mismatches were derived. We used substrates in which the lattice parameter was less than for the LBMO crystal one. It is shown that the temperature dependence of the film resistance in the low-temperature region does not depend on the film stress and is in good agreement with the calculation that takes into account the interaction of carriers with magnetic excitations in the presence of strongly correlated electron states. A nonmonotonic temperature dependence of the resistance of an LBMO film deposited on ferroelectric crystals PMN-PT that was observed. This feature is typical for manganites, and indicating the presence of ferromagnetism in the system was observed. Rare earth manganite with perovskite structure Re1-xAxMnO3 (Re-rare earth elements such as La or Nd and A-alkaline earth metals such as Sr, Ca, Ba) exhibits a wide range of unusual electrical and magnetic properties (see, for review [1]). The parameters of epitaxial films of these materials very often differ significantly from the properties of single crystals. As it has been shown in several studies [1, 2], the tension of the films due to mismatch with the substrate is the reason for the change in the electric and magnetic parameters of the films. It was shown that the three-dimensional compression of the crystal lattice increases the hopping probability amplitude in the double exchange model, which leads to an increase in the Curie temperature (TC), while the biaxial distortions of the Jahn-Teller type cause an increase in the localization of the electrons and decrease TС [3, 4]. Manganite films, for which TС is close to room temperature, are particularly attractive for practical applications. The ferromagnetic phase transition for a La0.7Ba0.3MnO3 (LBMO) crystal occurs at TC = 345 K [5]. In the LBMO crystal, a fairly large magnetostriction (up to 4 × 10 −4) was observed at a temperature equal to the Curie temperature [6]. The magnetic and resistive properties of LSMO films have been studied in a number of works [2, 5,6,7,8,9,10,11,12,13,14,15,16]. Usually, substrates from SrTiO3 (STO) [9, 13,14,15] were used. The film tension was changed either by changing the thickness of the LBMO film, or by changing the ratio of La and Ba. It was shown that in addition to the substrate-induced strain, oxygen content plays a very important role in determining the transport and magnetic properties of La1−xBaxMnO3 thin films [9]. For correct comparison of the effect of the stress on the film properties either film deposited on the different substrate under the same conditions [2], or piezo substrate are used [17, 18]. In LBMO films, when the film tension changes in piezo substrate, multiple resistive states arise. They are modulated by the magnetic field in a wide
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Dates et versions

hal-02127941 , version 1 (10-10-2020)

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G. Ovsyannikov, T. Shaikhulov, V. Shakhunov, Vladimir Preobrazhensky, T. Mathurin, et al.. Resistivity of Manganite Thin Film Under Strain. Journal of Superconductivity and Novel Magnetism, 2019, ⟨10.1007/s10948-019-5026-3⟩. ⟨hal-02127941⟩
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