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

1 Scopus citations

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

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials

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