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Title: Dopant Segregation and Giant Magnetoresistance in Manganese-doped Germanium

Abstract

Dopant segregation in a Mn{sub x}Ge{sub 1-x} dilute magnetic semiconductor leads to a remarkable self-assembly of Mn-rich nanocolumns, embedded in a fully compensated Ge matrix. Samples grown at 80 C display a giant positive magnetoresistance that correlates directly with the distribution of magnetic impurities. Annealing at 200 C increases Mn substitution in the host matrix above the threshold for the insulator-metal transition, while maintaining the columnar morphology, and results in global ferromagnetism with conventional negative magnetoresistance. The qualitative features of magnetism and transport in this nanophase material are thus extremely sensitive to the precise location and distribution of the magnetic dopants.

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [2];  [1];  [1]
  1. ORNL
  2. South Dakota School of Mines and Technology
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Center for Nanophase Materials Sciences
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931495
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review B; Journal Volume: 75; Journal Issue: 47
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; GERMANIUM; DOPED MATERIALS; MANGANESE; PHASE TRANSFORMATIONS; HEAT TREATMENTS; MORPHOLOGY; NANOSTRUCTURES; FERROMAGNETISM; MAGNETORESISTANCE

Citation Formats

Li, An-Ping, Zeng, Changgan, van Benthem, Klaus, Chisholm, Matthew F, Shen, Jian, Rao, Nageswara, Dixit, Suvasis, Feldman, Leonard C, Petukhov, Andre G, Foygel, M., Weitering, Harm H, and Gunter, Sandra Lynn. Dopant Segregation and Giant Magnetoresistance in Manganese-doped Germanium. United States: N. p., 2007. Web. doi:10.1103/PhysRevB.75.201201.
Li, An-Ping, Zeng, Changgan, van Benthem, Klaus, Chisholm, Matthew F, Shen, Jian, Rao, Nageswara, Dixit, Suvasis, Feldman, Leonard C, Petukhov, Andre G, Foygel, M., Weitering, Harm H, & Gunter, Sandra Lynn. Dopant Segregation and Giant Magnetoresistance in Manganese-doped Germanium. United States. doi:10.1103/PhysRevB.75.201201.
Li, An-Ping, Zeng, Changgan, van Benthem, Klaus, Chisholm, Matthew F, Shen, Jian, Rao, Nageswara, Dixit, Suvasis, Feldman, Leonard C, Petukhov, Andre G, Foygel, M., Weitering, Harm H, and Gunter, Sandra Lynn. Mon . "Dopant Segregation and Giant Magnetoresistance in Manganese-doped Germanium". United States. doi:10.1103/PhysRevB.75.201201.
@article{osti_931495,
title = {Dopant Segregation and Giant Magnetoresistance in Manganese-doped Germanium},
author = {Li, An-Ping and Zeng, Changgan and van Benthem, Klaus and Chisholm, Matthew F and Shen, Jian and Rao, Nageswara and Dixit, Suvasis and Feldman, Leonard C and Petukhov, Andre G and Foygel, M. and Weitering, Harm H and Gunter, Sandra Lynn},
abstractNote = {Dopant segregation in a Mn{sub x}Ge{sub 1-x} dilute magnetic semiconductor leads to a remarkable self-assembly of Mn-rich nanocolumns, embedded in a fully compensated Ge matrix. Samples grown at 80 C display a giant positive magnetoresistance that correlates directly with the distribution of magnetic impurities. Annealing at 200 C increases Mn substitution in the host matrix above the threshold for the insulator-metal transition, while maintaining the columnar morphology, and results in global ferromagnetism with conventional negative magnetoresistance. The qualitative features of magnetism and transport in this nanophase material are thus extremely sensitive to the precise location and distribution of the magnetic dopants.},
doi = {10.1103/PhysRevB.75.201201},
journal = {Physical Review B},
number = 47,
volume = 75,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Dopant deactivation and thermal annealing characteristics of metal-oxide-semiconductor capacitors fabricated on Ge/B-doped silicon after gamma irradiation or Fowler--Nordheim injection were investigated for the first time. A decrease of about 30% in active acceptor concentration was observed immediately after gamma irradiation or Fowler--Nordheim injection. Further deactivation of boron ({similar to}20%) occurred with annealing for temperatures of 80 {degree}C and higher. Hydrogen for the deactivation, which occurred during annealing, is thought to come from dissociation of weakly bonded Ge---H formed during the gamma irradiation or Fowler--Nordheim injection. Capacitors fabricated on conventional boron-doped substrates do not exhibit acceptor deactivation as a result ofmore » annealing following irradiation or injection. For annealing temperatures of 110 {degree}C and higher, the boron is first deactivated by the process noted above, and then is apparently reactivated by the dissociation of B---H bonds with hydrogen evolution from the structure.« less
  • Electron transport and magnetic properties of several compositions of the La{sub 1{minus}x}Sr{sub x{minus}z}Y{sub z}MnO{sub 3} system have been investigated in order to explore the effect of yttrium substitution on the magnetoresistance and related properties of these manganates. Yttrium substitution lowers the {Tc} and the insulator-metal transition temperature, while increasing the peak resistivity. A comparison of the properties of La{sub 1{minus}x}Sr{sub x{minus}z}Y{sub z}MnO{sub 3} with the corresponding La{sub 1{minus}x}Ca{sub x{minus}z}Y{sub z}MnO{sub 3} compositions shows that the observed properties can be related to the average size of the A-site cations.
  • A detailed study of doped LaMnO{sub 3} with fixed carrier concentration has revealed a direct relationship between the Curie temperature {ital T}{sub {ital c}} and the average ionic radius of the La site {l_angle}{ital r}{sub {ital A}}{r_angle}, which is varied by substituting rare earths of different ionic radii for La. With decreasing {l_angle}{ital r}{sub {ital A}}{r_angle} magnetic order and significant magnetoresistance occur at lower temperatures with increasing temperature hysteresis, and the magnitude of the magnetoresistance increases dramatically. The predominant structural effect of decreasing {l_angle}{ital r}{sub {ital A}}{r_angle} is to decrease the Mn{endash}O{endash}Mn bond angle, which is accompanied by slight variationsmore » in the Mn{endash}O bond distance. These results demonstrate that the notion of {open_quote}{open_quote}double exchange{close_quote}{close_quote} must be generalized to include changes in the Mn{endash}Mn electronic hopping element as a result of microstructural changes induced by composition, temperature and pressure variations. {copyright} {ital 1996 American Institute of Physics.}« less
  • La{sub 0.62}Tb{sub 0.05}Ca{sub 0.33}MnO{sub 3} and La{sub 0.6}Y{sub 0.07}Ca{sub 0.33}MnO{sub 3} have been studied in order to probe into the mechanisms responsible for the giant magnetoresistance ratios observed in this kind of compound. The experiments have shown a strong connection between the magnetotransport and magnetovolume properties. A large volume effect appears above {ital T}{sub {ital c}} which collapses with applied magnetic field or when the long range magnetic order sets in. Above {ital T}{sub {ital c}} the magnetostriction and magnetoresistance isotherms are highly correlated. Charge localization with local distortion appears to be responsible for the transport and volume properties atmore » zero field. Charge mobility and a more normal volume dependence on temperature are restored by applying high enough magnetic fields. {copyright} {ital 1996 American Institute of Physics.}« less