Effects of lattice distortion on the physical properties and surface morphology of magnetoresistive perovskite epitaxial films

Abstract

The effects of lattice distortion on the physical properties of La 0.7 Ca 0.3 MnO 3 epitaxial films are investigated. Our results suggest that larger substrate-induced lattice distortion gives rise to larger zero-field resistivity and larger negative magnetoresistance. Similar effects are also observed in samples of different thicknesses and on the same substrate material, with larger resistivity and magnetoresistance associated with thinner samples. In addition to x-ray diffraction spectroscopy, the degrees of lattice distortion in different samples are further verified by the surface topography taken with a low-temperature scanning tunneling microscope. Quantitative analyses of the transport properties suggest that the high-temperature (T→T C) colossal magnetoresistance ͑CMR͒ in the manganites is consistent with the conduction of lattice polarons induced by the Jahn-Teller coupling, and that the low-temperature (TӶT C) magnetoresistance may be attributed to the magnetic domain wall scattering. In contrast, the absence of the Jahn-Teller coupling and the large conductivity in La 0.5 Ca 0.5 CoO 3 epitaxial films yield much smaller negative magnetoresistance, which may be attributed to disorder-spin scattering.

On-line phase transition in La1−xSrxMnO3(0.28 ≤ x ≤ 0.36) perovskites through ultrasonic studies

“…On the other hand, when the coupling arises due to linear magnetostriction effect, the anomalous behaviour exists both in longitudinal and shear wave velocities. The above interaction shows a strong spin-lattice coupling during the FM transition [35,38,40]. The absence of pronounced maxima/minima in U L , U S and L , except at T c , confirms the absence of CO within the temperature range of 298-420 K of this investigation.…”

“…It is interesting to note from Figures 1-3 that pronounced maxima/minima are observed in U L , U S and L at 380, 375, and 372 K, respectively. These observations are different from the normal behaviour observed in many other perovskite manganite materials [30,38,39]. The anomalies observed both in U L and U S (Figures 1 and 2) at T c (380, 375 and 372 K, respectively for, x ¼ 0.28, 0.31 and 0.36) are ascribed due to the transition from the PM state to the FM state.…”

Microstructures of La1−xAx(A = Ca or Sr)MnO3−δthin films by liquid-delivery metalorganic chemical vapor deposition

“…7,[9][10][11][12][13][14][15][16][17][18] The lattice mismatch between the thin film and the substrate is a consequential parameter having a great influence on the structure, morphology, and strain of the thin films. The films grown on a large lattice mismatched substrate, such as MgO with a mismatch of 8% usually have relaxed lattice parameters which are close to the bulk material.…”

Comparison of the Magnetic, Conduction, and Magnetotransport Behaviors of Ba2+‐ and Al3+‐Doped La0.67Ca0.33MnO3

“…Basically, the conduction behavior of La 1− x M x MnO 3 is mainly determined by the characteristics of the network of Mn 3+ –O–Mn 4+ . It is now clear that either external pressure or doping can change lattice strain and deformations, which in turn would affect the Mn 3+ –O–Mn 4+ bond angle and length and have dramatic impacts on the magnetism and electrical properties of La 1− x M x MnO 3 6–11 . Although the modification of the crucial Mn 3+ –O–Mn 4+ network via the doping at the A or B site has been studied individually, it would provide a deep insight to enable a comparison between them.…”