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Title: Microstructure, magnetoresistance, and magnetic properties of pulsed-laser-deposited external, internal, and mixed-doped lanthanum manganite films

Abstract

In this article we report our studies on the microstructure, magnetoresistance (MR) behavior, and magnetic properties of the La[sub 1[minus]x[minus]y]Ca[sub x]MnO[sub 3] system in thin-film form. By varying the values of [ital x] and [ital y] in La[sub 1[minus]x[minus]y]Ca[sub x]MnO[sub 3], we have synthesized an external- (x=0.3, y=0), an internal- (x=0, y=0.3), and a mixed-doped (x=0.2, y=0.1) system with the same Mn[sup 3+]/Mn[sup 4+] ratio. Thin films of these materials have been grown [ital in situ] on (100) LaAlO[sub 3] substrates using a pulsed-laser-deposition technique. Atomic force microscopy, x-ray diffraction and high-resolution transmission electron microscopy measurements carried out on these films have shown that the films are smooth, highly crystalline, and epitaxial on the (100) LaAlO[sub 3] substrates. Electrical resistance and magnetoresistance have been measured in the 10[endash]300 K range in magnetic fields up to 5 T using a superconducting quantum interference device magnetometer. The MR ratios (calculated using the expression, [R[sub 0][minus]R[sub H]]/R[sub H], where R[sub 0] and R[sub H] are resistances in zero and applied fields) of the La[sub 0.7]Ca[sub 0.3]MnO[sub 3] (x=0.3, y=0), La[sub 0.7]MnO[sub 3] (x=0, y=0.3), and La[sub 0.7]Ca[sub 0.2]MnO[sub 3] (x=0.2, y=0.1) films are found to be 825[percent], 700[percent], and 750[percent] at 200, 240,more » and 220 K, respectively. The MR ratios of these films, calculated using the expression, [R[sub 0][minus]R[sub H]]/R[sub H], are 91[percent], 87[percent], and 88[percent], respectively, at the same temperatures. The variation in the insulator-to-metal transition and the MR ratio is attributed to internal chemical pressure and vacancy localization effects. Below T[sub c]/2 (T[sub c] is paramagnetic-to-ferromagnetic transition temperature), resistance increases as T[sup 2] for La[sub 0.7]Ca[sub 0.3]MnO[sub 3] and La[sub 0.7]Ca[sub 0.2]MnO[sub 3] while it increases as T[sup 5/2] for La[sub 0.7]MnO[sub 3]. The T[sup 2] and T[sup 5/2] dependence of resistance suggests that the transport is predominantly governed by an electron[endash]electron scattering and a combination of electron[endash]electron, electron[endash]phonon, and electron[endash]magnon scattering, respectively. High-temperature resistance has been observed to be consistent with small polaron hopping conductivity for all three systems. Magnetization measurements carried out on the films show that the films have reasonably square hysteresis loops with sharp T[sub c][close quote]s. Below T[sub c]/2, the magnetization decreases as T[sup 2] for La[sub 0.7]Ca[sub 0.2]MnO[sub 3] and La[sub 0.7]MnO[sub 3], suggesting single-particle excitations in them, while it decreases as T[sup 3/2] for La[sub 0.7]Ca[sub 0.3]MnO[sub 3], representing collective oscillations in this system. [copyright] [ital 1999 American Institute of Physics.]« less

Authors:
; ;  [1];  [2];  [3]
  1. (Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611-6400 (United States))
  2. (Department of Electrical Engineering, North Carolina AT State University, Greensboro, North Carolina 27411 (United States))
  3. (MRST Device Engineering Division, Motorola Inc., Austin, Texas (United States))
Publication Date:
OSTI Identifier:
6194705
Alternate Identifier(s):
OSTI ID: 6194705
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 86:6; Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ATOMIC FORCE MICROSCOPY; CALCIUM COMPOUNDS; CALCIUM OXIDES; DOPED MATERIALS; ELECTRON-ELECTRON INTERACTIONS; LANTHANUM COMPOUNDS; LANTHANUM OXIDES; MAGNETIZATION; MAGNETORESISTANCE; MAGNONS; MANGANESE OXIDES; MICROSTRUCTURE; PHASE TRANSFORMATIONS; THIN FILMS; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION; ALKALINE EARTH METAL COMPOUNDS; CHALCOGENIDES; COHERENT SCATTERING; DIFFRACTION; ELECTRIC CONDUCTIVITY; ELECTRICAL PROPERTIES; ELECTRON MICROSCOPY; FILMS; INTERACTIONS; LEPTON-LEPTON INTERACTIONS; MANGANESE COMPOUNDS; MATERIALS; MICROSCOPY; OXIDES; OXYGEN COMPOUNDS; PARTICLE INTERACTIONS; PHYSICAL PROPERTIES; QUASI PARTICLES; RARE EARTH COMPOUNDS; SCATTERING; TRANSITION ELEMENT COMPOUNDS 360204* -- Ceramics, Cermets, & Refractories-- Physical Properties

Citation Formats

Pietambaram, S.V., Kumar, D., Singh, R.K., Lee, C.B., and Kaushik, V.S. Microstructure, magnetoresistance, and magnetic properties of pulsed-laser-deposited external, internal, and mixed-doped lanthanum manganite films. United States: N. p., 1999. Web. doi:10.1063/1.371208.
Pietambaram, S.V., Kumar, D., Singh, R.K., Lee, C.B., & Kaushik, V.S. Microstructure, magnetoresistance, and magnetic properties of pulsed-laser-deposited external, internal, and mixed-doped lanthanum manganite films. United States. doi:10.1063/1.371208.
Pietambaram, S.V., Kumar, D., Singh, R.K., Lee, C.B., and Kaushik, V.S. Wed . "Microstructure, magnetoresistance, and magnetic properties of pulsed-laser-deposited external, internal, and mixed-doped lanthanum manganite films". United States. doi:10.1063/1.371208.
@article{osti_6194705,
title = {Microstructure, magnetoresistance, and magnetic properties of pulsed-laser-deposited external, internal, and mixed-doped lanthanum manganite films},
author = {Pietambaram, S.V. and Kumar, D. and Singh, R.K. and Lee, C.B. and Kaushik, V.S.},
abstractNote = {In this article we report our studies on the microstructure, magnetoresistance (MR) behavior, and magnetic properties of the La[sub 1[minus]x[minus]y]Ca[sub x]MnO[sub 3] system in thin-film form. By varying the values of [ital x] and [ital y] in La[sub 1[minus]x[minus]y]Ca[sub x]MnO[sub 3], we have synthesized an external- (x=0.3, y=0), an internal- (x=0, y=0.3), and a mixed-doped (x=0.2, y=0.1) system with the same Mn[sup 3+]/Mn[sup 4+] ratio. Thin films of these materials have been grown [ital in situ] on (100) LaAlO[sub 3] substrates using a pulsed-laser-deposition technique. Atomic force microscopy, x-ray diffraction and high-resolution transmission electron microscopy measurements carried out on these films have shown that the films are smooth, highly crystalline, and epitaxial on the (100) LaAlO[sub 3] substrates. Electrical resistance and magnetoresistance have been measured in the 10[endash]300 K range in magnetic fields up to 5 T using a superconducting quantum interference device magnetometer. The MR ratios (calculated using the expression, [R[sub 0][minus]R[sub H]]/R[sub H], where R[sub 0] and R[sub H] are resistances in zero and applied fields) of the La[sub 0.7]Ca[sub 0.3]MnO[sub 3] (x=0.3, y=0), La[sub 0.7]MnO[sub 3] (x=0, y=0.3), and La[sub 0.7]Ca[sub 0.2]MnO[sub 3] (x=0.2, y=0.1) films are found to be 825[percent], 700[percent], and 750[percent] at 200, 240, and 220 K, respectively. The MR ratios of these films, calculated using the expression, [R[sub 0][minus]R[sub H]]/R[sub H], are 91[percent], 87[percent], and 88[percent], respectively, at the same temperatures. The variation in the insulator-to-metal transition and the MR ratio is attributed to internal chemical pressure and vacancy localization effects. Below T[sub c]/2 (T[sub c] is paramagnetic-to-ferromagnetic transition temperature), resistance increases as T[sup 2] for La[sub 0.7]Ca[sub 0.3]MnO[sub 3] and La[sub 0.7]Ca[sub 0.2]MnO[sub 3] while it increases as T[sup 5/2] for La[sub 0.7]MnO[sub 3]. The T[sup 2] and T[sup 5/2] dependence of resistance suggests that the transport is predominantly governed by an electron[endash]electron scattering and a combination of electron[endash]electron, electron[endash]phonon, and electron[endash]magnon scattering, respectively. High-temperature resistance has been observed to be consistent with small polaron hopping conductivity for all three systems. Magnetization measurements carried out on the films show that the films have reasonably square hysteresis loops with sharp T[sub c][close quote]s. Below T[sub c]/2, the magnetization decreases as T[sup 2] for La[sub 0.7]Ca[sub 0.2]MnO[sub 3] and La[sub 0.7]MnO[sub 3], suggesting single-particle excitations in them, while it decreases as T[sup 3/2] for La[sub 0.7]Ca[sub 0.3]MnO[sub 3], representing collective oscillations in this system. [copyright] [ital 1999 American Institute of Physics.]},
doi = {10.1063/1.371208},
journal = {Journal of Applied Physics},
issn = {0021-8979},
number = ,
volume = 86:6,
place = {United States},
year = {1999},
month = {9}
}