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Title: Colossal terahertz magnetoresistance at room temperature in epitaxial La 0.7Sr 0.3MnO 3 nanocomposites and single-phase thin films

Abstract

Colossal magnetoresistance (CMR) is demonstrated at terahertz (THz) frequencies by using terahertz time-domain magnetospectroscopy to examine vertically aligned nanocomposites (VANs) and planar thin films of La 0.7Sr 0.3MnO 3. At the Curie temperature (room temperature), the THz conductivity of the VAN was dramatically enhanced by over 2 orders of magnitude under the application of a magnetic field with a non-Drude THz conductivity that increased with frequency. The direct current (dc) CMR of the VAN is controlled by extrinsic magnetotransport mechanisms such as spin-polarized tunneling between nanograins. In contrast, we find that THz CMR is dominated by intrinsic, intragrain transport: the mean free path was smaller than the nanocolumn size, and the planar thin-film exhibited similar THz CMR to the VAN. Surprisingly, the observed colossal THz magnetoresistance suggests that the magnetoresistance can be large for alternating current motion on nanometer length scales, even when the magnetoresistance is negligible on the macroscopic length scales probed by dc transport. This suggests that colossal magnetoresistance at THz frequencies may find use in nanoelectronics and in THz optical components controlled by magnetic fields. As a result, the VAN can be scaled in thickness while retaining a high structural quality and offers a larger THz CMRmore » at room temperature than the planar film.« less

Authors:
ORCiD logo [1];  [1];  [2];  [1]; ORCiD logo [3];  [4];  [5];  [5]
  1. Univ. of Warwick, Coventry (United Kingdom)
  2. Univ. of Oxford, Oxford (United Kingdom)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  4. Univ. at Buffalo, Buffalo, NY (United States)
  5. Univ. of Cambridge, Cambridge (United Kingdom)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1364556
Report Number(s):
LA-UR-17-22535
Journal ID: ISSN 1530-6984
Grant/Contract Number:
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 17; Journal Issue: 4; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; Material Science

Citation Formats

Lloyd-Hughes, James, Mosley, C. D. W., Jones, S. P. P., Lees, M. R., Chen, Aiping, Jia, Quan Xi, Choi, E. -M., and MacManus-Driscoll, J. L. Colossal terahertz magnetoresistance at room temperature in epitaxial La0.7Sr0.3MnO3 nanocomposites and single-phase thin films. United States: N. p., 2017. Web. doi:10.1021/acs.nanolett.7b00231.
Lloyd-Hughes, James, Mosley, C. D. W., Jones, S. P. P., Lees, M. R., Chen, Aiping, Jia, Quan Xi, Choi, E. -M., & MacManus-Driscoll, J. L. Colossal terahertz magnetoresistance at room temperature in epitaxial La0.7Sr0.3MnO3 nanocomposites and single-phase thin films. United States. doi:10.1021/acs.nanolett.7b00231.
Lloyd-Hughes, James, Mosley, C. D. W., Jones, S. P. P., Lees, M. R., Chen, Aiping, Jia, Quan Xi, Choi, E. -M., and MacManus-Driscoll, J. L. Mon . "Colossal terahertz magnetoresistance at room temperature in epitaxial La0.7Sr0.3MnO3 nanocomposites and single-phase thin films". United States. doi:10.1021/acs.nanolett.7b00231. https://www.osti.gov/servlets/purl/1364556.
@article{osti_1364556,
title = {Colossal terahertz magnetoresistance at room temperature in epitaxial La0.7Sr0.3MnO3 nanocomposites and single-phase thin films},
author = {Lloyd-Hughes, James and Mosley, C. D. W. and Jones, S. P. P. and Lees, M. R. and Chen, Aiping and Jia, Quan Xi and Choi, E. -M. and MacManus-Driscoll, J. L.},
abstractNote = {Colossal magnetoresistance (CMR) is demonstrated at terahertz (THz) frequencies by using terahertz time-domain magnetospectroscopy to examine vertically aligned nanocomposites (VANs) and planar thin films of La0.7Sr0.3MnO3. At the Curie temperature (room temperature), the THz conductivity of the VAN was dramatically enhanced by over 2 orders of magnitude under the application of a magnetic field with a non-Drude THz conductivity that increased with frequency. The direct current (dc) CMR of the VAN is controlled by extrinsic magnetotransport mechanisms such as spin-polarized tunneling between nanograins. In contrast, we find that THz CMR is dominated by intrinsic, intragrain transport: the mean free path was smaller than the nanocolumn size, and the planar thin-film exhibited similar THz CMR to the VAN. Surprisingly, the observed colossal THz magnetoresistance suggests that the magnetoresistance can be large for alternating current motion on nanometer length scales, even when the magnetoresistance is negligible on the macroscopic length scales probed by dc transport. This suggests that colossal magnetoresistance at THz frequencies may find use in nanoelectronics and in THz optical components controlled by magnetic fields. As a result, the VAN can be scaled in thickness while retaining a high structural quality and offers a larger THz CMR at room temperature than the planar film.},
doi = {10.1021/acs.nanolett.7b00231},
journal = {Nano Letters},
number = 4,
volume = 17,
place = {United States},
year = {Mon Mar 13 00:00:00 EDT 2017},
month = {Mon Mar 13 00:00:00 EDT 2017}
}

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  • Vertically aligned nanocomposite (VAN) (La{sub 0.7}Sr{sub 0.3}MnO{sub 3}){sub 1−x}:(CeO{sub 2}){sub x} (LSMO:CeO{sub 2}) thin films have been grown on SrTiO{sub 3} (001) substrates by pulsed laser deposition. Tunable magnetoresistance properties as well as microstructures are demonstrated in these VAN films by modulating the film composition (x = 0, 0.3, 0.4, 0.45, 0.5, and 0.55). The sample of x = 0.3 shows a large low-field magnetoresistance (LFMR) in a high temperature range, i.e., over 10% at the range of 280 K to 320 K under 1 T and with a peak value of ∼13.5% at 310 K. In addition, a vast enhancement of LFMR in a low temperature rangemore » of 20–150 K with peak of ≈34.3% at 45 K for 1 T could be achieved with x = 0.5. The enhanced LFMR properties can be attributed to both the phase boundary induced spin fluctuation and the magnetic tunneling effect through vertical ferromagnetic/insulator/ferromagnetic structures. The observed enhanced LFMR performance, especially at high temperatures, as well as its simple growth method, offers a great potential for LSMO:CeO{sub 2}nanocomposites to be used in spintronic devices in a large temperature range.« less
  • We report the growth and properties of La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/YBa{sub 2}Cu{sub 3}O{sub 7−δ}/La{sub 0.7}Sr{sub 0.3}MnO{sub 3} LSMO/YBCO/LSMO epitaxial trilayer films, fabricated on SrTiO{sub 3} substrate using pulsed laser deposition technique. From x-ray diffraction and high resolution x-ray diffraction measurements, it is confirmed that the grown trilayered films are single phase and epitaxial in nature. Magneto-transport and magnetic properties are found to be dependent on the thickness of YBCO spacer layer. We infer that for fixed thickness of top and bottom LSMO layers, superconductivity is completely suppressed. At 100 K, the hysteresis loops reveal the ferromagnetic signature of trilayered film.more » At room temperature, we obtain a butterfly type scenario, signifies the co-existence of ferromagnetic and antiferromagnetic interaction. In addition, at room temperature, the YBCO spacer layer allowing the top and bottom LSMO layers to interact antiferromagnetically.« less
  • We report the electrical-transport, magnetoresistance and magnetic properties of the hole doped La{sub 0.7}Ca{sub 0.3}MnO{sub 3} (LCMO) and La{sub 0.7}Ca{sub 0.24}Sr{sub 0.06}MnO{sub 3} (LCSMO) single crystals. It was prepared using floating zone technique. The resistivity data shows the metal to insulator transition (T{sub MI}) occurs at 211 K along c-axis and T{sub MI} = 185 K the ab-plane for LCMO and T{sub MI} = 290 K along the c-axis and T{sub MI} = 280 K along the ab-plane for LCSMO single crystals. It is observed that the T{sub MI} is higher along the c-axis as compared to that in the ab-plane, consequently signifying moremore » favorable hoping of electrons is along the c-axis. The ac-susceptibility measurement shows that this material exhibits ferromagnetic to paramagnetic transition temperature (TC) at 206 K for LCMO and T{sub C} = 277 K for LCSMO single crystals. For magnetic memory device application point of view, the sample shows the maximum MR of 98% for LCMO and 80% for LCSMO single crystals at 8T applied magnetic field. Doping small amount of Sr (0.06%) reveals that the electronic and magnetic phase transition in CMR single crystal increases substantially and useful for device application. This is first time such type of comparative study in these manganite single crystals.« less
  • To obtain low field magnetoresistance (MR) in manganites, we have introduced a geometrically constrained magnetic domain wall (DW) in La{sub 0.7}Sr{sub 0.3}MnO{sub 3} micrometric devices. Nanoconstrictions artificially induced using high resolution e-beam lithography are shown to effectively reduce the DW width leading to strongly enhanced DW resistance. Sharp and large resistance switches result from the appearance and annihilation of the DWs. Room temperature sharp resistance switches, with a MR of 16%, are evidenced in a manganite-based device. {copyright} 2001 American Institute of Physics.
  • 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