New insights into the transport and field-enhancement effects in sol-gel derived colossal magnetoresistive thin films

Kannan M. Krishnan, H. L. Ju, H. C. Sohn, C. Nelson, A. R. Modak

Research output: Contribution to journalConference article

1 Citation (Scopus)

Abstract

The transport mechanism underlying the colossal magnetoresistance (CMR) of doped manganites is not yet understood and their technological applications are limited by the high fields (approximately 1 T) required to obtain any significant MR. Following the development of a polymeric chemical synthesis route, we have investigated the O2p unoccupied density of states in sol-gel derived La1-xSrxMnO3 (0≤x≤0.7) thin films grown epitaxially on LaAlO3, by electron energy-loss spectroscopy at sub-eV resolution. The spectra show a distinct prepeak in the OK edge at the Fermi level, the intensity of which correlates directly with the conductivity of the film. Similar correlation was also obtained for La0.7Sr0.3MnO3-z annealed in vacuum to obtain well defined oxygen content (z) in the film. This confirms that the charge carriers in these manganese perovskites have significant oxygen 2p hole character and suggests that the `double exchange' mechanism has to be modified. In another set of experiments we have studied room-temperature field amplification effects to enhance the low-field sensitivity of La0.7Sr0.3MnO3-z films sandwiched between two thin rectangular slices of either α-Fe or Mn-Zn ferrite. This field amplification leads to an enhanced low-field MR value as high as 6% at an external field of 500 Oe which is 6 times the value observed without the amplification.

Original languageEnglish
Pages (from-to)139-144
Number of pages6
JournalMaterials Research Society Symposium - Proceedings
Volume477
Publication statusPublished - 1997 Dec 1

Fingerprint

Sol-gels
Amplification
gels
Thin films
augmentation
thin films
Colossal magnetoresistance
Oxygen
Manganites
Electron energy loss spectroscopy
oxygen
perovskites
Manganese
Fermi level
Charge carriers
Ferrite
manganese
charge carriers
ferrites
Temperature distribution

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials

Cite this

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title = "New insights into the transport and field-enhancement effects in sol-gel derived colossal magnetoresistive thin films",
abstract = "The transport mechanism underlying the colossal magnetoresistance (CMR) of doped manganites is not yet understood and their technological applications are limited by the high fields (approximately 1 T) required to obtain any significant MR. Following the development of a polymeric chemical synthesis route, we have investigated the O2p unoccupied density of states in sol-gel derived La1-xSrxMnO3 (0≤x≤0.7) thin films grown epitaxially on LaAlO3, by electron energy-loss spectroscopy at sub-eV resolution. The spectra show a distinct prepeak in the OK edge at the Fermi level, the intensity of which correlates directly with the conductivity of the film. Similar correlation was also obtained for La0.7Sr0.3MnO3-z annealed in vacuum to obtain well defined oxygen content (z) in the film. This confirms that the charge carriers in these manganese perovskites have significant oxygen 2p hole character and suggests that the `double exchange' mechanism has to be modified. In another set of experiments we have studied room-temperature field amplification effects to enhance the low-field sensitivity of La0.7Sr0.3MnO3-z films sandwiched between two thin rectangular slices of either α-Fe or Mn-Zn ferrite. This field amplification leads to an enhanced low-field MR value as high as 6{\%} at an external field of 500 Oe which is 6 times the value observed without the amplification.",
author = "Krishnan, {Kannan M.} and Ju, {H. L.} and Sohn, {H. C.} and C. Nelson and Modak, {A. R.}",
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New insights into the transport and field-enhancement effects in sol-gel derived colossal magnetoresistive thin films. / Krishnan, Kannan M.; Ju, H. L.; Sohn, H. C.; Nelson, C.; Modak, A. R.

In: Materials Research Society Symposium - Proceedings, Vol. 477, 01.12.1997, p. 139-144.

Research output: Contribution to journalConference article

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T1 - New insights into the transport and field-enhancement effects in sol-gel derived colossal magnetoresistive thin films

AU - Krishnan, Kannan M.

AU - Ju, H. L.

AU - Sohn, H. C.

AU - Nelson, C.

AU - Modak, A. R.

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AB - The transport mechanism underlying the colossal magnetoresistance (CMR) of doped manganites is not yet understood and their technological applications are limited by the high fields (approximately 1 T) required to obtain any significant MR. Following the development of a polymeric chemical synthesis route, we have investigated the O2p unoccupied density of states in sol-gel derived La1-xSrxMnO3 (0≤x≤0.7) thin films grown epitaxially on LaAlO3, by electron energy-loss spectroscopy at sub-eV resolution. The spectra show a distinct prepeak in the OK edge at the Fermi level, the intensity of which correlates directly with the conductivity of the film. Similar correlation was also obtained for La0.7Sr0.3MnO3-z annealed in vacuum to obtain well defined oxygen content (z) in the film. This confirms that the charge carriers in these manganese perovskites have significant oxygen 2p hole character and suggests that the `double exchange' mechanism has to be modified. In another set of experiments we have studied room-temperature field amplification effects to enhance the low-field sensitivity of La0.7Sr0.3MnO3-z films sandwiched between two thin rectangular slices of either α-Fe or Mn-Zn ferrite. This field amplification leads to an enhanced low-field MR value as high as 6% at an external field of 500 Oe which is 6 times the value observed without the amplification.

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