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 language | English (US) |
---|---|
Title of host publication | Materials Research Society Symposium - Proceedings |
Editors | H.M. Ng, M. Wraback, K. Hiramatsu, N. Grandjean |
Pages | 551-555 |
Number of pages | 5 |
Volume | 798 |
State | Published - 2003 |
Event | GaN and Related Alloys - 2003 - Boston, MA, United States Duration: Dec 1 2003 → Dec 5 2003 |
Other
Other | GaN and Related Alloys - 2003 |
---|---|
Country/Territory | United States |
City | Boston, MA |
Period | 12/1/03 → 12/5/03 |
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials