Bulk electronic structure of the dilute magnetic semiconductor Ga1−xMnxAs through hard X-ray angle-resolved photoemission

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Abstract

A detailed understanding of the origin of the magnetism in dilute magnetic semiconductors is crucial to their development for applications. Using hard X-ray angle-resolved photoemission (HARPES) at 3.2 keV, we investigate the bulk electronic structure of the prototypical dilute magnetic semiconductor Ga0.97Mn0.03As, and the reference undoped GaAs. The data are compared to theory based on the coherent potential approximation and fully relativistic one-step-model photoemission calculations including matrix-element effects. Distinct differences are found between angle-resolved, as well as angle-integrated, valence spectra of Ga0.97Mn0.03As and GaAs, and these are in good agreement with theory. Direct observation of Mn-induced states between the GaAs valence-band maximum and the Fermi level, centred about 400 meV below this level, as well as changes throughout the full valence-level energy range, indicates that ferromagnetism in Ga1−xMnxAs must be considered to arise from both pd exchange and double exchange, thus providing a more unifying picture of this controversial material.

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Figure 1: HARPES measurements and one-step theory for bulk GaAs and Ga0.97Mn0.03As.
Figure 2: One-step theory spectral functions for GaAs and Ga0.97Mn0.03As.
Figure 3: Angle-integrated valence-band spectra for GaAs and Ga0.97Mn0.03As.
Figure 4: Analysis of the near-Fermi-edge region in the HARPES data.
Figure 5: GaAs and Ga0.97Mn0.03 As theoretical DOS.

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Acknowledgements

This work was funded by the US Department of Energy under Contract No. DE-AC02-05CH11231, including salary and travel support for C.S.F. and A.X.G. The authors are grateful to HiSOR, Hiroshima University and JAEA/SPring-8 for the development of HXPS at BL15XU of SPring-8. The experiments at BL15XU were performed under the approval of NIMS Beamline Station (Proposal No. 2009A4906). This work was partially supported by the Nanotechnology Network Project, MEXT, Japan. Research at Stanford was supported through the Stanford Institute for Materials and Energy Science and the LCLS by the US Department of Energy, Office of Basic Energy Sciences. Financial support from German funding agencies DFG (SFB 689, EB 154/18 and EB 154/20) and the German ministry BMBF (05K10WMA) is also gratefully acknowledged (J.M., J.B. and H.E.).

Author information

A.X.G. and S.U. carried out the experiments, with assistance from Y.Y. and under the supervision of K.K. and C.S.F. Data normalization and analysis were performed by A.X.G and under the supervision of C.S.F. Theoretical calculations were carried out by J.M. J.B. and H.E. (one-step theory), and by L.P. with support from C.M.S. (additional free-electron final-state theory band structure). Samples were grown by P.R.S. under the supervision on O.D.D. Additional supporting measurements were carried out by J.F. under the supervision of G.P.

Correspondence to A. X. Gray.

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Gray, A., Minár, J., Ueda, S. et al. Bulk electronic structure of the dilute magnetic semiconductor Ga1−xMnxAs through hard X-ray angle-resolved photoemission. Nature Mater 11, 957–962 (2012) doi:10.1038/nmat3450

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