Observation of ferromagnetism above 900 K in Cr-GaN and Cr-AlN
| Autor: | M. B. Simmonds, Stephen Y. Wu, David J. Smith, H. X. Liu, Lin Gu, L. Montes, Nathan Newman, N. R. Dilley, Rakesh Singh |
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| Rok vydání: | 2004 |
| Předmět: | |
| DOI: | 10.48550/arxiv.cond-mat/0402103 |
| Popis: | We report the observation of ferromagnetism at over 900K in Cr-GaN and Cr-AlN thin films. The saturation magnetization moments in our best films of Cr-GaN and Cr-AlN at low temperatures are 0.42 and 0.6 u_B/Cr atom, respectively, indicating that 14% and 20%, of the Cr atoms, respectively, are magnetically active. While Cr-AlN is highly resistive, Cr-GaN exhibits thermally activated conduction that follows the exponential law expected for variable range hopping between localized states. Hall measurements on a Cr-GaN sample indicate a mobility of 0.06 cm^2/V.s, which falls in the range characteristic of hopping conduction, and a free carrier density (1.4E20/cm^3), which is similar in magnitude to the measured magnetically-active Cr concentration (4.9E19/cm^3). A large negative magnetoresistance is attributed to scattering from loose spins associated with non-ferromagnetic impurities. The results indicate 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. Comment: 14 pages, 4 figures, submitted to APL |
| Databáze: | OpenAIRE |
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