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Title: Magnetic and Chemical Nonuniformity in Ga1-xMnxAs Films as Probed by Polarized Neutron and X-ray Reflectometry

Authors:
; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930587
Report Number(s):
BNL-80829-2008-JA
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review B: Condensed Matter and Materials Physics; Journal Volume: 74
Country of Publication:
United States
Language:
English
Subject:
national synchrotron light source

Citation Formats

Kirby,B., Borchers, J., Rhyne, J., O'Donovan, K., Velthuis, S., Roy, S., Sanchez-Hanke, C., Wojtowicz, T., Liu, X., and et al. Magnetic and Chemical Nonuniformity in Ga1-xMnxAs Films as Probed by Polarized Neutron and X-ray Reflectometry. United States: N. p., 2006. Web. doi:10.1103/PhysRevB.74.245304.
Kirby,B., Borchers, J., Rhyne, J., O'Donovan, K., Velthuis, S., Roy, S., Sanchez-Hanke, C., Wojtowicz, T., Liu, X., & et al. Magnetic and Chemical Nonuniformity in Ga1-xMnxAs Films as Probed by Polarized Neutron and X-ray Reflectometry. United States. doi:10.1103/PhysRevB.74.245304.
Kirby,B., Borchers, J., Rhyne, J., O'Donovan, K., Velthuis, S., Roy, S., Sanchez-Hanke, C., Wojtowicz, T., Liu, X., and et al. Sun . "Magnetic and Chemical Nonuniformity in Ga1-xMnxAs Films as Probed by Polarized Neutron and X-ray Reflectometry". United States. doi:10.1103/PhysRevB.74.245304.
@article{osti_930587,
title = {Magnetic and Chemical Nonuniformity in Ga1-xMnxAs Films as Probed by Polarized Neutron and X-ray Reflectometry},
author = {Kirby,B. and Borchers, J. and Rhyne, J. and O'Donovan, K. and Velthuis, S. and Roy, S. and Sanchez-Hanke, C. and Wojtowicz, T. and Liu, X. and et al.},
abstractNote = {},
doi = {10.1103/PhysRevB.74.245304},
journal = {Physical Review B: Condensed Matter and Materials Physics},
number = ,
volume = 74,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • We have used complementary neutron and x-ray reflectivity techniques to examine the depth profiles of a series of as-grown and annealed Ga{sub 1-x}Mn{sub x}As thin films. A magnetization gradient is observed for two as-grown films and originates from a nonuniformity of Mn at interstitial sites, and not from local variations in Mn at Ga sites. Furthermore, we see that the depth-dependent magnetization can vary drastically among as-grown Ga{sub 1-x}Mn{sub x}As films despite being deposited under seemingly similar conditions. These results imply that the depth profile of interstitial Mn is dependent not only on annealing, but is also extremely sensitive tomore » initial growth conditions. We observe that annealing improves the magnetization by producing a surface layer that is rich in Mn and O, indicating that the interstitial Mn migrates to the surface. Finally, we expand upon our previous neutron reflectivity study of Ga{sub 1-x}Mn{sub x}As, by showing how the depth profile of the chemical composition at the surface and through the film thickness is directly responsible for the complex magnetization profiles observed in both as-grown and annealed films.« less
  • We have used complementary neutron and x-ray reflectivity techniques to examine the depth profiles of a series of as-grown and annealed Ga{sub 1-x}Mn{sub x}As thin films. A magnetization gradient is observed for two as-grown films and originates from a nonuniformity of Mn at interstitial sites, and not from local variations in Mn at Ga sites. Furthermore, we see that the depth-dependent magnetization can vary drastically among as-grown Ga{sub 1-x}Mn{sub x}As films despite being deposited under seemingly similar conditions. These results imply that the depth profile of interstitial Mn is dependent not only on annealing, but is also extremely sensitive tomore » initial growth conditions. We observe that annealing improves the magnetization by producing a surface layer that is rich in Mn and O, indicating that the interstitial Mn migrates to the surface. Finally, we expand upon our previous neutron reflectivity study of Ga{sub 1-x}Mn{sub x}As, by showing how the depth profile of the chemical composition at the surface and through the film thickness is directly responsible for the complex magnetization profiles observed in both as-grown and annealed films.« less
  • The evolution of the magnetic structure of multilayer [Fe (35 {angstrom})/Gd (50 {angstrom}){sub 5}] with variation in temperature and an applied magnetic field was determined using a complementary approach combining polarized neutron and X-ray resonant magnetic reflectometry. Self-consistent simultaneous analysis of X-ray and neutron spectra allowed us to determine the elemental and depth profiles in the multilayer structure with unprecedented accuracy, including the identification of an inhomogeneous intralayer magnetic structure with near-atomic resolution.
  • X-ray absorption near-edge structure (XANES) is used to study the characteristics of different sites of Mn in the Ga1-xMnxN dilute magnetic semiconductor (DMS) with zinc-blende structure. The XANES spectra of representative Mn occupation sites (substitutional MnGa, interstitial MnI, MnGa-MnI dimer and Mn cluster) in GaN lattice are theoretically calculated and compared with experimental results. The substitutional Mn in GaN is characterized by a pre-edge peak at 2.0 eV and a post-edge multiple-scattering peak at 29.1 eV. The peaks shift in position and drop in intensity dramatically for the interstitial MnI and MnGa-MnI dimmer, and disappear completely for Mn clusters. Wemore » propose that the distinct characteristics of Mn K-edge XANES spectra for different Mn sites favor to discriminate Mn occupations in GaMnN DMS.« less
  • The electronic and magnetic effects of intentional compensation with non-magnetic donors are investigated in the ferromagnetic semiconductors Ga1-xMnxAs and Ga1-xMnxP synthesized using ion implantation and pulsed-laser melting (II-PLM). It is demonstrated that compensation with non-magnetic donors and MnI have similarqualitative effects on materials properties. With compensation TC decreases, resistivity increases, and stronger magnetoresistance and anomalous Hall effect attributed to skew scattering are observed. Ga1-xMnxAs can be controllably compensated with Te through a metal-insulator transition through which the magnetic and electrical properties vary continuously. The resistivity of insulating Ga1-xMnxAs:Te can be described by thermal activation to the mobility edge and simply-activatedmore » hopping transport. Ga1-xMnxP doped with S is insulating at all compositions but shows decreasing TC with compensation. The existence of a ferromagnetic insulating state in Ga1-xMnxAs:Te and Ga1-xMnxP:S having TCs of the same order as the uncompensated materials demonstrates that localized holes are effective at mediating ferromagnetism in ferromagnetic semiconductors through the percolation of ferromagnetic 'puddles' which at low temperatures.« less