Influence of Oxygen Vacancies on Transport Properties of La_2/3Ca_1/3MnO_3-y Films Grown on SrTiO₃ Substrates

Abstract

We prepared La 2=3 Ca 1=3 MnO 3Ày films with various oxygen contents on SrTiO 3 substrates and measured the temperaturedependent resistivity of the manganite films under tensile stress due to the lattice mismatch between manganites and singlecrystal substrates. The effect of oxygen vacancies on the transport properties of the films was investigated. The experimental results reveal that the dependence of temperature on the resistivity of fully oxygenated films can be attributed to the adiabatic small-polaron conduction and unconventional one-magnon scattering at temperatures above and far below the insulator-metal (I-M) transition temperature, respectively. However, for highly oxygen-deficient films, the temperature-dependent resistivity can be ascribed to Mott's variable-range-hopping and small polaron metallic conduction at temperatures above and far below the I-M transition temperature, respectively.

Mixed‐Valence Perovskite Thin Films by Polymer‐Assisted Deposition

“…Ferromagnetism in the film annealed at 850°C develops over a wide temperature range. Similar behavior was observed in La 0.8 MnO 3 films and La 2/3 Ca 1/3 MnO 3 films prepared by PLD 29,30 . In their report, they have observed the sharpening of the transition and increase in transition temperature, T c , with the increase in the annealing temperature and oxygen pressure, which was believed to be due to change in oxygen content with annealing temperature.…”

“…In addition, the present films were annealed for 2 h, whereas in some reports films were annealed for 12 h to achieve high contents of the oxygen and thus higher transition temperature near T c in the corresponding bulk material 32,33 . It should be noted that the value of T c and the broadness of the transition in the perovskite manganite thin films can vary from that in the bulk of the same composition due to many factors such as stress (compressive or tensile), oxygen content, annealing, texture/orientation of film, and grain size/grain, etc 3,17,18,29,30,32,33 . In the same composition of LCMO film deposited on LAO substrate by sol–gel technique, Bae and Wang 34 reported T c at 228 K, which was lower and the transition was much broader than that observed in the present case.…”

“…Similar behavior was observed in La 0.8 MnO 3 films and La 2/3 Ca 1/3 MnO 3 films prepared by PLD. 29,30 In their report, they have observed the sharpening of the transition and increase in transition temperature, T c , with the increase in the annealing temperature and oxygen pressure, which was believed to be due to change in oxygen content with annealing temperature. In conclusion, this kind of change of M behavior can come from compositional (different composition in grains and grain boundaries) or structural (two phases) inhomogeneities or a change in oxygen stoichiometry.…”

Cation uniformity and magnetic properties of La0.7Sr0.3Mn0.5Fe0.5O3 thin films

“…For sample (1), the out-of-plane lattice parameter was calculated as c¼3.900Å corresponding to a slight tetragonal distortion under compressive strain characterized by a c/a ratio¼ 1.007. After O 2 annealing, the out-of-plane lattice parameter decreased to 3.885Å (c/a ratio ¼1.003), possibly due to a decreased oxygen vacancy concentration in the film [15,[21][22][23]. For sample (2) grown with a target-substrate distance¼5.5 cm, the out-ofplane lattice constant was calculated as 3.916Å (c/a ratio¼1.011), which corresponds to an increase in the unit cell volume compared to sample (1).…”

Structural variability in La0.5Sr0.5TiO3±δ thin films

“…With increasing O 2 pressure, the out-ofplane lattice parameter gradually decreases most likely due to a decrease in unit cell volume with reduced oxygen vacancy concentration. [10][11][12] However, for films grown in high vacuum ($10 À6 Torr) and cooled in !200 Torr O 2 pressure, a broad film peak at low 2h values as well as extra peaks ( Fig. 1 and S1 (Ref.…”