Electron-induced stabilization of ferromagnetism in Ga1 xGdxN

SUMMARY In summary, we have investigated in detail the elec-tronic and magnetic properties of Ga 1−x Gd x N. We findthat because of the coupling between the Gd f and hosts states, this system shows some unique behavior that isdrastically different from TM-doped GaN. The exchangesplitting at the CBM is negative. The coupling betweenGd atoms is found to be antiferromagnetic, if no donorsare present, but it become ferromagnetic when enoughdonors are present in the system. We also proposed amodel that may explain the colossal magnetic momentsobserved in this system in the very dilute limit, showingthat it should be directly related to the polarization ofdonor electrons. ACKNOWLEDGMENTS The work at NREL is funded by the U.S. Departmentof Energy, Office ofScience, Basic EnergySciences, underContract No. DE-AC36-99GO10337 to NREL. [1] I. Zutic, J. Fabian, S. Das Sarma, Rev. Mod. Phys. 76,323 (2004).[2] D. D. Awschalom and R. K. Kawakami, Nature (London)408, 923 (2000).[3] T. Dietl, H. Ohno, F. Matsukura, J. Cibert, and D. Fer-rand, Science 287, 1019 (2000).[4] S. Dhar, O. Brandt, A. Trampert, L. Daweritz, K. J.Friedland, K. H. Ploog, J. Keller, B. Beschoten, and G.Guntherodt, Appl. Phys. Lett. 82, 2077 (2003).[5] J. I. Pankove and T. D. Moustakas, Gallium Nitride(GaN) I (Academic, San Diego, 1998).[6] D, C, Look, J. W. Hemsky, and J. R. Sizelove, Phys. Rev.Lett. 82, 2552 (1999).[7] N. Teraguchi, A. Suzuki, Y. Nanishi, Y.-K. Zhou, M.Hashimoto and H. Asahi, Sol. State Comm. 122, 651(2002).[8] S. Dhar, O. Brandt, M. Ramsteiner, V. F. Sapega, andK. H. Ploog, Phys. Rev. Lett. 94, 037205 (2005).[9] H. Asahi, Y. K. Zhou, M. Hashimoto, M. S. Kim, X.J. Li, S. Emura, and S. Hasegawa, J. Phys.: Condens.Matter 16, S5555 (2004).[10] J. M. D. Coey, M. Venkatesan, and C. B. Fitzgerald,Nature Materials 4, 173 (2005).[11] S.-H. Wei and H. Krakauer, Phys. Rev. Lett. 55, 1200(1985); D. J. Singh, Planewaves, Pseudopotentials, andthe LAPW Method, (Kluwer, Boston, 1994).[12] H. J. Monkhorst and J. P. Pack, Phys. Rev. B 13, 5188(1976).[13] D. X. Li, Y. Haga, H. Shida, T. Suzuki, Y. S. Kwon andG. Kido, J. Phys.: Condens. Matter 9, 10777 (1997).[14] A. Janotti, S.-H. Wei, and L. Bellaiche, Appl. Phys. Lett.82, 766 (2003).[15] S.-H. Wei and Alex Zunger, Phys. Rev. B 48, 6111(1993).[16] J. P. Perdew and Y. Wang, Phys. Rev. B 45, 13244(1992).[17] H. Hashimoto, S. Emura, R. Asano, H. Tanaka, N. Ter-aguchi, A. Suzuki, Y. Nanishi, T. Honma, N. Umesaki,H. Asahi , Phys. Stat. Sol. (c) 0, 2650 (2003).[18] W. R. L. Lambrecht, Phys. Rev. B 62, 13538 (2000).[19] G. M. Dalpian, S.-H. Wei, X. G. Gong, A. J. R. da Silva,and A. Fazzio, cond-mat/0504084.[20] Y. K. Zhou, M. S. Kim, X. J. Li, S. Kimura, A. Kaneta,Y. Kawakami, Sg. Fujita, S. Emura, S. Hasegawa and H.Asahi , J. Phys.: Condens. Matter 16, S5743 (2004).