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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. 2016. "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 = 2016,
month = 6
}
  • Crystallographic structure of sol-gel-processed lead-free (K,Na)NbO{sub 3} (KNN) epitaxial films on [100]-cut SrTiO{sub 3} single-crystalline substrates was investigated for a deeper understanding of its piezoelectric response. Lattice parameter measurement by high-resolution X-ray diffraction and transmission electron microscopy revealed that the orthorhombic KNN films on SrTiO{sub 3} (100) surfaces are [010] oriented (b-axis-oriented) rather than commonly identified c-axis orientation. Based on the crystallographic orientation and corresponding ferroelectric domain structure investigated by piezoresponse force microscopy, the superior piezoelectric property along b-axis of epitaxial KNN films than other orientations can be explained.
  • 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
  • The integration of oxides with semiconductors is important for the technological advancement of the next generation electronics. Concomitant ferroelectric and antiferromagnetic (AF) behavior is demonstrated in single crystal BiFeO{sub 3} (BFO) films grown on 20 nm SrTiO{sub 3} (STO) virtual substrates on Si(100) using molecular beam epitaxy (MBE). STO thin films are grown in an oxide MBE chamber by co-deposition of Sr, Ti, and molecular O{sub 2}. Careful control of the O{sub 2} during nucleation produced commensurate growth of STO on Si. The sequence of the steps allows for the suppression of an amorphous SiO{sub 2} layer. This STO(20 nm)/Simore » structure was used as a virtual substrate for MBE deposition of BFO on Si without breaking vacuum. BFO was deposited using Fe and O{sub 2} plasma with an overpressure of Bi flux, the growth rate was controlled by the incoming Fe flux. The reflection high energy electron diffraction image shows a 2-D growth front with a 6-fold surface reconstruction under optimized O{sub 2} pressure of 5 Multiplication-Sign 10{sup -8} mbar. Cross-sectional transmission electron microscopy (TEM) confirms the high crystallinity of the films and shows sharp, atomically flat interfaces. The selected area diffraction pattern (SADP) reveals that BFO grows in a distorted rhombohedral crystal structure. X-ray diffraction does not show formation of second phases and is consistent with the TEM and SADP results. The BFO films show AF behavior with a Neel temperature that exceeds 350 K, as expected (T{sub N} = 673 K) and with a residual ferromagnetic behavior that decreases with film thickness and is consistent with the G-type AF due to the canted spins. The saturation magnetization per unit volume for a 40 nm thick film was 180 emu/cm{sup 3} at an in-plane magnetic field of 8 kOe. The ferroelectric behavior of the films was verified using piezoresponse force microscopy.« less
  • Normal-metal/insulator/superconductor (NIS) junctions were fabricated using thin films of YBa/sub 2/Cu/sub 3/O/sub 7-//sub x/ (YBCO) or ErBa/sub 2/Cu/sub 3/O/sub 7-//sub x/. These were epitaxially grown on single-crystal SrTiO/sub 3/ by the activated reactive evaporation method. For some NIS junctions prepared on SrTiO/sub 3/ (110) substrates, we observed multipeaks in the differential conductance versus voltage curve. NIS junctions using single-crystal YBCO films on SrTiO/sub 3/ (100) showed a set of peaks, from which we obtained a gap parameter of 11.5 +- 1.5 meV at 4.4 K and a coupling constant of 3.2 +- 0.4.