Abstract

We report ferromagnetism at over 900 K in Cr-GaN and Cr-AlN thin films. The magnetic properties vary as a function of Cr concentration with 60%, and 20%, of the Cr being magnetically active at 3% doping in GaN, and 7% in AlN, respectively. In the GaN sample with the highest magnetically active Cr (60%), channeling Rutherford backscattering indicates that over 70% of Cr impurities are located on substitutional sites. These results give indisputable evidence that substitutional Cr defects are involved in the magnetic behavior. While Cr-AlN is highly resistive, Cr-GaN exhibits properties characteristic of hopping conduction including T -1/2 resistivity dependence and small Hall mobility (0.06 cm 2/V s). A large negative magnetoresistance is attributed to the influence of the magnetic field on the quantum interference between the many paths linking two hopping sites. The results strongly suggest that ferromagnetism in Cr-GaN and Cr-AlN can be attributed to the double exchange mechanism as a result of hopping between near-midgap substitutional Cr impurity bands.

Original languageEnglish (US)
Pages (from-to)4076-4078
Number of pages3
JournalApplied Physics Letters
Volume85
Issue number18
DOIs
StatePublished - Nov 1 2004

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ferromagnetism
impurities
backscattering
magnetic properties
interference
conduction
electrical resistivity
defects
thin films
magnetic fields

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

Cite this

Observation of ferromagnetism above 900 K in Cr-GaN and Cr-AlN. / Liu, H. X.; Wu, Stephen Y.; Singh, Rakesh; Gu, Lin; Smith, David; Newman, Nathan; Dilley, N. R.; Montes, L.; Simmonds, M. B.

In: Applied Physics Letters, Vol. 85, No. 18, 01.11.2004, p. 4076-4078.

Research output: Contribution to journalArticle

Liu, HX, Wu, SY, Singh, R, Gu, L, Smith, D, Newman, N, Dilley, NR, Montes, L & Simmonds, MB 2004, 'Observation of ferromagnetism above 900 K in Cr-GaN and Cr-AlN', Applied Physics Letters, vol. 85, no. 18, pp. 4076-4078. https://doi.org/10.1063/1.1812581
Liu, H. X. ; Wu, Stephen Y. ; Singh, Rakesh ; Gu, Lin ; Smith, David ; Newman, Nathan ; Dilley, N. R. ; Montes, L. ; Simmonds, M. B. / Observation of ferromagnetism above 900 K in Cr-GaN and Cr-AlN. In: Applied Physics Letters. 2004 ; Vol. 85, No. 18. pp. 4076-4078.
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abstract = "We report ferromagnetism at over 900 K in Cr-GaN and Cr-AlN thin films. The magnetic properties vary as a function of Cr concentration with 60{\%}, and 20{\%}, of the Cr being magnetically active at 3{\%} doping in GaN, and 7{\%} in AlN, respectively. In the GaN sample with the highest magnetically active Cr (60{\%}), channeling Rutherford backscattering indicates that over 70{\%} of Cr impurities are located on substitutional sites. These results give indisputable evidence that substitutional Cr defects are involved in the magnetic behavior. While Cr-AlN is highly resistive, Cr-GaN exhibits properties characteristic of hopping conduction including T -1/2 resistivity dependence and small Hall mobility (0.06 cm 2/V s). A large negative magnetoresistance is attributed to the influence of the magnetic field on the quantum interference between the many paths linking two hopping sites. The results strongly suggest that ferromagnetism in Cr-GaN and Cr-AlN can be attributed to the double exchange mechanism as a result of hopping between near-midgap substitutional Cr impurity bands.",
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AU - Liu, H. X.

AU - Wu, Stephen Y.

AU - Singh, Rakesh

AU - Gu, Lin

AU - Smith, David

AU - Newman, Nathan

AU - Dilley, N. R.

AU - Montes, L.

AU - Simmonds, M. B.

PY - 2004/11/1

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N2 - We report ferromagnetism at over 900 K in Cr-GaN and Cr-AlN thin films. The magnetic properties vary as a function of Cr concentration with 60%, and 20%, of the Cr being magnetically active at 3% doping in GaN, and 7% in AlN, respectively. In the GaN sample with the highest magnetically active Cr (60%), channeling Rutherford backscattering indicates that over 70% of Cr impurities are located on substitutional sites. These results give indisputable evidence that substitutional Cr defects are involved in the magnetic behavior. While Cr-AlN is highly resistive, Cr-GaN exhibits properties characteristic of hopping conduction including T -1/2 resistivity dependence and small Hall mobility (0.06 cm 2/V s). A large negative magnetoresistance is attributed to the influence of the magnetic field on the quantum interference between the many paths linking two hopping sites. The results strongly suggest that ferromagnetism in Cr-GaN and Cr-AlN can be attributed to the double exchange mechanism as a result of hopping between near-midgap substitutional Cr impurity bands.

AB - We report ferromagnetism at over 900 K in Cr-GaN and Cr-AlN thin films. The magnetic properties vary as a function of Cr concentration with 60%, and 20%, of the Cr being magnetically active at 3% doping in GaN, and 7% in AlN, respectively. In the GaN sample with the highest magnetically active Cr (60%), channeling Rutherford backscattering indicates that over 70% of Cr impurities are located on substitutional sites. These results give indisputable evidence that substitutional Cr defects are involved in the magnetic behavior. While Cr-AlN is highly resistive, Cr-GaN exhibits properties characteristic of hopping conduction including T -1/2 resistivity dependence and small Hall mobility (0.06 cm 2/V s). A large negative magnetoresistance is attributed to the influence of the magnetic field on the quantum interference between the many paths linking two hopping sites. The results strongly suggest that ferromagnetism in Cr-GaN and Cr-AlN can be attributed to the double exchange mechanism as a result of hopping between near-midgap substitutional Cr impurity bands.

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