Synthesis and characterization of high quality ferromagnetic Cr-doped GaN and AlN thin films with curie temperatures above 900K

Stephen Y. Wu, H. X. Liu, Lin Gu, Rakesh Singh, M. Van Schilfgaarde, David Smith, N. R. Dilley, L. Montes, M. B. Simmonds, Nathan Newman

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Reactive MBE growth was used to synthesize ferromagnetic Cr-doped GaN and AlN thin films with Curie temperatures above 900K. 2% Cr-doped GaN and 7% Cr-doped AlN were found to have a saturation magnetization moment of 0.42 and 0.6 μ B/Cr atom, indicating that ∼14% and ∼20% of the Cr, respectively, are magnetically active. Structural characterization using X-ray diffraction (XRD) and transmission electron microscopy (TEM) did not find evidence of a ferromagnetic secondary phase. Electrical characterization indicate that the resistivity of the Cr-doped GaN films depends exponentially on temperature as R=R oexp[(T o/T) 1/2], characteristic of variable range hopping. In contrast, Cr-doped AlN films are highly resistive. Local spin density functional calculations predict that Cr forms a deep level defect in both systems and the t 2 level falls approximately at midgap. Our theoretical and experimental results indicate that ferromagnetism in Cr-doped GaN and AlN arises as a result of the double exchange mechanism within the partially filled Cr t 2 band.

Original languageEnglish (US)
Title of host publicationMaterials Research Society Symposium - Proceedings
EditorsH.M. Ng, M. Wraback, K. Hiramatsu, N. Grandjean
Pages551-555
Number of pages5
Volume798
StatePublished - 2003
EventGaN and Related Alloys - 2003 - Boston, MA, United States
Duration: Dec 1 2003Dec 5 2003

Other

OtherGaN and Related Alloys - 2003
CountryUnited States
CityBoston, MA
Period12/1/0312/5/03

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Curie temperature
Thin films
Ferromagnetism
Saturation magnetization
Molecular beam epitaxy
Density functional theory
Transmission electron microscopy
X ray diffraction
Atoms
Defects
Temperature

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials

Cite this

Wu, S. Y., Liu, H. X., Gu, L., Singh, R., Van Schilfgaarde, M., Smith, D., ... Newman, N. (2003). Synthesis and characterization of high quality ferromagnetic Cr-doped GaN and AlN thin films with curie temperatures above 900K. In H. M. Ng, M. Wraback, K. Hiramatsu, & N. Grandjean (Eds.), Materials Research Society Symposium - Proceedings (Vol. 798, pp. 551-555)

Synthesis and characterization of high quality ferromagnetic Cr-doped GaN and AlN thin films with curie temperatures above 900K. / Wu, Stephen Y.; Liu, H. X.; Gu, Lin; Singh, Rakesh; Van Schilfgaarde, M.; Smith, David; Dilley, N. R.; Montes, L.; Simmonds, M. B.; Newman, Nathan.

Materials Research Society Symposium - Proceedings. ed. / H.M. Ng; M. Wraback; K. Hiramatsu; N. Grandjean. Vol. 798 2003. p. 551-555.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Wu, SY, Liu, HX, Gu, L, Singh, R, Van Schilfgaarde, M, Smith, D, Dilley, NR, Montes, L, Simmonds, MB & Newman, N 2003, Synthesis and characterization of high quality ferromagnetic Cr-doped GaN and AlN thin films with curie temperatures above 900K. in HM Ng, M Wraback, K Hiramatsu & N Grandjean (eds), Materials Research Society Symposium - Proceedings. vol. 798, pp. 551-555, GaN and Related Alloys - 2003, Boston, MA, United States, 12/1/03.
Wu SY, Liu HX, Gu L, Singh R, Van Schilfgaarde M, Smith D et al. Synthesis and characterization of high quality ferromagnetic Cr-doped GaN and AlN thin films with curie temperatures above 900K. In Ng HM, Wraback M, Hiramatsu K, Grandjean N, editors, Materials Research Society Symposium - Proceedings. Vol. 798. 2003. p. 551-555
Wu, Stephen Y. ; Liu, H. X. ; Gu, Lin ; Singh, Rakesh ; Van Schilfgaarde, M. ; Smith, David ; Dilley, N. R. ; Montes, L. ; Simmonds, M. B. ; Newman, Nathan. / Synthesis and characterization of high quality ferromagnetic Cr-doped GaN and AlN thin films with curie temperatures above 900K. Materials Research Society Symposium - Proceedings. editor / H.M. Ng ; M. Wraback ; K. Hiramatsu ; N. Grandjean. Vol. 798 2003. pp. 551-555
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abstract = "Reactive MBE growth was used to synthesize ferromagnetic Cr-doped GaN and AlN thin films with Curie temperatures above 900K. 2{\%} Cr-doped GaN and 7{\%} Cr-doped AlN were found to have a saturation magnetization moment of 0.42 and 0.6 μ B/Cr atom, indicating that ∼14{\%} and ∼20{\%} of the Cr, respectively, are magnetically active. Structural characterization using X-ray diffraction (XRD) and transmission electron microscopy (TEM) did not find evidence of a ferromagnetic secondary phase. Electrical characterization indicate that the resistivity of the Cr-doped GaN films depends exponentially on temperature as R=R oexp[(T o/T) 1/2], characteristic of variable range hopping. In contrast, Cr-doped AlN films are highly resistive. Local spin density functional calculations predict that Cr forms a deep level defect in both systems and the t 2 level falls approximately at midgap. Our theoretical and experimental results indicate that ferromagnetism in Cr-doped GaN and AlN arises as a result of the double exchange mechanism within the partially filled Cr t 2 band.",
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AU - Wu, Stephen Y.

AU - Liu, H. X.

AU - Gu, Lin

AU - Singh, Rakesh

AU - Van Schilfgaarde, M.

AU - Smith, David

AU - Dilley, N. R.

AU - Montes, L.

AU - Simmonds, M. B.

AU - Newman, Nathan

PY - 2003

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N2 - Reactive MBE growth was used to synthesize ferromagnetic Cr-doped GaN and AlN thin films with Curie temperatures above 900K. 2% Cr-doped GaN and 7% Cr-doped AlN were found to have a saturation magnetization moment of 0.42 and 0.6 μ B/Cr atom, indicating that ∼14% and ∼20% of the Cr, respectively, are magnetically active. Structural characterization using X-ray diffraction (XRD) and transmission electron microscopy (TEM) did not find evidence of a ferromagnetic secondary phase. Electrical characterization indicate that the resistivity of the Cr-doped GaN films depends exponentially on temperature as R=R oexp[(T o/T) 1/2], characteristic of variable range hopping. In contrast, Cr-doped AlN films are highly resistive. Local spin density functional calculations predict that Cr forms a deep level defect in both systems and the t 2 level falls approximately at midgap. Our theoretical and experimental results indicate that ferromagnetism in Cr-doped GaN and AlN arises as a result of the double exchange mechanism within the partially filled Cr t 2 band.

AB - Reactive MBE growth was used to synthesize ferromagnetic Cr-doped GaN and AlN thin films with Curie temperatures above 900K. 2% Cr-doped GaN and 7% Cr-doped AlN were found to have a saturation magnetization moment of 0.42 and 0.6 μ B/Cr atom, indicating that ∼14% and ∼20% of the Cr, respectively, are magnetically active. Structural characterization using X-ray diffraction (XRD) and transmission electron microscopy (TEM) did not find evidence of a ferromagnetic secondary phase. Electrical characterization indicate that the resistivity of the Cr-doped GaN films depends exponentially on temperature as R=R oexp[(T o/T) 1/2], characteristic of variable range hopping. In contrast, Cr-doped AlN films are highly resistive. Local spin density functional calculations predict that Cr forms a deep level defect in both systems and the t 2 level falls approximately at midgap. Our theoretical and experimental results indicate that ferromagnetism in Cr-doped GaN and AlN arises as a result of the double exchange mechanism within the partially filled Cr t 2 band.

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