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Title: Determination of magnetic parameters in La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/SrTiO{sub 3} thin films using EMCD

Abstract

It is well known that the magnetic state of the La{sub 0.7}Sr{sub 0.3}MnO{sub 3} (LSMO) thin-film heterostructure is strongly correlated with the lattice, spin, orbital, and charge states, since these influence the electric and magnetic transport properties even on the unit-cell level. Therefore, understanding the material's magnetic properties on the nanoscale is important for the development of novel applications. The recently developed electron magnetic-circular dichroism (EMCD) technique allows the determination of atomic site-specific magnetic information via the use of transmitted electrons; however, its sensitivity is not high enough to quantitatively acquire magnetic information in many weak magnetism systems. Here, we utilized a dynamical diffraction-effect assisted EMCD technique to quantitatively determine the spin and orbital magnetic moment of LSMO/SrTiO{sub 3} thin films on the nanometer scale using a transmission electron microscope. Further, data processing was optimized to enhance the intensity of the EMCD signals for manganese, which have very weak magnetism at room temperature. High signal-to-noise ratio and accurate quantitative magnetic measurement are eventually achieved. Finally, the spin magnetic moments (0.73 ± 0.26 μ{sub B}) are derived, and we also limited the ratio of the orbital to spin magnetic moment within an interval of (−0.03, 0.01). Our results not only present the nanoscale magneticmore » parameters of LSMO/SrTiO{sub 3}, but also demonstrate how the measurement limit of the spin (or orbital) magnetic moment can be achieved, which is via the developed dynamical diffraction effect assisted EMCD technique.« less

Authors:
; ; ;  [1]
  1. National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE) and the State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)
Publication Date:
OSTI Identifier:
22590795
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 108; Journal Issue: 24; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CHARGE STATES; DATA PROCESSING; DIFFRACTION; MAGNETIC CIRCULAR DICHROISM; MAGNETIC MOMENTS; MAGNETIC PROPERTIES; MAGNETISM; MANGANESE; NANOSTRUCTURES; NOISE; SENSITIVITY; SIGNALS; SIGNAL-TO-NOISE RATIO; SPIN; STRONTIUM TITANATES; TEMPERATURE RANGE 0273-0400 K; THIN FILMS; TRANSMISSION ELECTRON MICROSCOPY

Citation Formats

Li, Gen, Song, Dongsheng, Li, Zhi Peng, and Zhu, Jing, E-mail: jzhu@mail.tsinghua.edu.cn. Determination of magnetic parameters in La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/SrTiO{sub 3} thin films using EMCD. United States: N. p., 2016. Web. doi:10.1063/1.4954168.
Li, Gen, Song, Dongsheng, Li, Zhi Peng, & Zhu, Jing, E-mail: jzhu@mail.tsinghua.edu.cn. Determination of magnetic parameters in La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/SrTiO{sub 3} thin films using EMCD. United States. doi:10.1063/1.4954168.
Li, Gen, Song, Dongsheng, Li, Zhi Peng, and Zhu, Jing, E-mail: jzhu@mail.tsinghua.edu.cn. Mon . "Determination of magnetic parameters in La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/SrTiO{sub 3} thin films using EMCD". United States. doi:10.1063/1.4954168.
@article{osti_22590795,
title = {Determination of magnetic parameters in La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/SrTiO{sub 3} thin films using EMCD},
author = {Li, Gen and Song, Dongsheng and Li, Zhi Peng and Zhu, Jing, E-mail: jzhu@mail.tsinghua.edu.cn},
abstractNote = {It is well known that the magnetic state of the La{sub 0.7}Sr{sub 0.3}MnO{sub 3} (LSMO) thin-film heterostructure is strongly correlated with the lattice, spin, orbital, and charge states, since these influence the electric and magnetic transport properties even on the unit-cell level. Therefore, understanding the material's magnetic properties on the nanoscale is important for the development of novel applications. The recently developed electron magnetic-circular dichroism (EMCD) technique allows the determination of atomic site-specific magnetic information via the use of transmitted electrons; however, its sensitivity is not high enough to quantitatively acquire magnetic information in many weak magnetism systems. Here, we utilized a dynamical diffraction-effect assisted EMCD technique to quantitatively determine the spin and orbital magnetic moment of LSMO/SrTiO{sub 3} thin films on the nanometer scale using a transmission electron microscope. Further, data processing was optimized to enhance the intensity of the EMCD signals for manganese, which have very weak magnetism at room temperature. High signal-to-noise ratio and accurate quantitative magnetic measurement are eventually achieved. Finally, the spin magnetic moments (0.73 ± 0.26 μ{sub B}) are derived, and we also limited the ratio of the orbital to spin magnetic moment within an interval of (−0.03, 0.01). Our results not only present the nanoscale magnetic parameters of LSMO/SrTiO{sub 3}, but also demonstrate how the measurement limit of the spin (or orbital) magnetic moment can be achieved, which is via the developed dynamical diffraction effect assisted EMCD technique.},
doi = {10.1063/1.4954168},
journal = {Applied Physics Letters},
number = 24,
volume = 108,
place = {United States},
year = {Mon Jun 13 00:00:00 EDT 2016},
month = {Mon Jun 13 00:00:00 EDT 2016}
}
  • La{sub 0.7}Sr{sub 0.3}MnO{sub 3} (LSMO) thin films with a thickness d of 10, 20, 60, and 100 nm were grown on 20-nm-thick SrTiO{sub 3}-buffered (100) silicon substrates by a reactive molecular beam epitaxy. For all samples, x-ray diffraction (XRD) revealed an excellent epitaxy with in-plane cubic [100] and [010] axes of LSMO. The XRD measured values of the out-of-plane lattice parameter suggest that the strain state does not vary significantly from sample to sample. A super conducting quantum interference device reveals that the room temperature magnetization at saturation increases with d and nearly reaches the bulk value for d =more » 100 nm; the Curie temperature ranges in the 320-350 K interval, to compare to 360 K in the bulk. Ferromagnetic resonance (FMR) in cavity (at 9.5 GHz) and microstrip FMR used to investigate the dynamic magnetic properties, revealed a fourfold anisotropy showing its easy axes along the [110] and [110] directions. In the thickest samples (d > 20 nm), the FMR spectra present two distinct resonant modes. This splitting is presumably due to the simultaneous presence of two different magnetic phases.« less
  • La{sub 0.7}Sr{sub 0.3}MnO{sub 3} (LSMO) thin films were successfully prepared on (100), (110), and (111) oriented SrTiO{sub 3} substrates by chemical solution deposition method. The structural, magnetic, and magnetotransport properties were systematically studied. X-ray diffraction θ-2θ and ϕ-scan measurements results show that all the films have perfect crystalline orientation and in-plane alignment. Both the Curie temperature and metal-insulator transition temperature are almost the same for all the three orientations, about 339 K. The magnetoresistance value (MR value, defined as (R{sub M} − R{sub 0})/R{sub 0} × 100%, where R{sub M} and R{sub 0} are the resistivity with and without applied magnetic field) for the filmsmore » reaches maximum near the Curie temperature. Both the magnetization and MR value for (100) direction LSMO are the largest, and meanwhile for (111) direction are the smallest. The saturation magnetization decreases approximately proportional to T{sup 2} at low temperature (T < T{sub c}/2) for all the oriented film. Inversely, the resistivity increases proportional to T{sup 2} in the same temperature range, which can be attributed to the electron-electron scattering.« less
  • We have fabricated ferromagnet-insulator-ferromagnet junctions using a ramp-edge geometry based on (La{sub 0.7}Sr{sub 0.3})MnO{sub 3} ferromagnetic electrodes and a SrTiO{sub 3} insulator. Pulsed laser deposition was used to deposit the multilayer thin films and the devices were patterned using photolithography and ion milling. As expected from the spin-dependent tunneling, the junction magnetoresistance is dependent on the relative orientation of the magnetization in the electrodes. A junction magnetoresistance (JMR) as large as 30{percent} is observed at low temperatures and low fields. In addition, we have found that JMR is reduced at high temperatures (T{gt}100K) and decreases monotonically with increasing field atmore » high fields (0.5T{lt}H{lt}1T). Possible causes for these are also discussed. {copyright} {ital 1998 American Institute of Physics.}« less
  • Oxygen K -edge electron-energy-loss spectra have been measured for La{sub 1{minus}x}Sr {sub x}MnO{sub 3} (0{le}x{le}0.7) and La{sub 0.7}Sr {sub 0.3}MnO {sub z} thin films as a function of x and z . The spectra show a prepeak at the Fermi level, corresponding to transitions to empty states in the O{sub 2p} band, at the threshold of the K edge around 529eV. This prepeak systematically increases with an increase in conductivity through divalent doping (x) or oxygen content (z) . This confirms that these materials are charge-transfer-type oxides with carriers having significant oxygen 2p hole character. We argue that, the doublemore » exchange mechanism has to include the role of oxygen hole density to satisfactorily describe their transport properties. {copyright} {ital 1997} {ital The American Physical Society}« less
  • Oxygen K-edge electron-energy-loss spectra have been measured for La{sub 1{minus}x}Sr{sub x}MnO{sub 3} (0 {le} x {le} 0.7) and La{sub 0.7}Sr{sub 0.3}MnO{sub z} thin films as a function of x and z. The spectra show a prepeak at the Fermi level, corresponding to transitions to empty states in the O{sub 2p} band, at the threshold of the K edge around 529 eV. This prepeak systematically increases with an increase in conductivity through divalent doping (x) or oxygen content (z). This confirms that these materials are charge-transfer-type oxides with carriers having significant oxygen 2p hole character. We argue that, the double exchangemore » mechanism has to include the role of oxygen hole density to satisfactorily describe their transport properties.« less