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Title: Metastable phase formation and magnetic properties of the Fe-Nb system studied by atomistic modeling and ion beam mixing

Abstract

With the aid of ab initio calculations, an n-body Fe-Nb embedded-atom potential is first constructed and then applied to study the crystal-to-amorphous phase transition through molecular dynamic simulations. The simulations determine that the glass-forming range of the Fe-Nb system is 18-83 at. % of Nb. In ion beam mixing experiments, five Fe-Nb multilayered films with overall compositions of Fe{sub 85}Nb{sub 15}, Fe{sub 75}Nb{sub 25}, Fe{sub 55}Nb{sub 45}, Fe{sub 25}Nb{sub 75}, and Fe{sub 15}Nb{sub 85}, respectively, are irradiated by 200 keV xenon ions to doses in the range of (1-7)x10{sup 15}Xe{sup +}/cm{sup 2}. The result shows that the Fe-Nb metallic glasses can be synthesized within a composition range of 25-75 at. % of Nb, matching reasonably well the theoretical prediction. Moreover, in the Fe{sub 55}Nb{sub 45} sample, a fcc-structured alloy phase with a large lattice constant of a{approx_equal}0.408 nm was obtained at a dose of 3x10{sup 15} Xe{sup +}/cm{sup 2} and the associated magnetic moment per Fe atom was measured to be 2.41{mu}{sub B}. The observed magnetic moment is much greater than the initial value of 1.42{mu}{sub B} in the bcc-Fe lattice and can thus serve as evidence confirming the high-spin ferromagnetic state of fcc Fe predicted by ab initio calculations.more » Interestingly, further irradiation induced phase separation in the Fe{sub 55}Nb{sub 45} sample, i.e., irradiation to a dose of 5x10{sup 15} Xe{sup +}/cm{sup 2} results in the growth of a fractal pattern consisting of Fe{sub 72}Nb{sub 28} nanoclusters embedded in Fe{sub 35}Nb{sub 65} matrix. The formation mechanism of the metastable phases as well as that of the fractal pattern observed in the Fe-Nb system was discussed in terms of the atomic collision theory and the well-known cluster-diffusion-limited-aggregation model.« less

Authors:
; ;  [1]
  1. Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)
Publication Date:
OSTI Identifier:
21137393
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 104; Journal Issue: 1; Other Information: DOI: 10.1063/1.2955716; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AMORPHOUS STATE; ATOM COLLISIONS; BCC LATTICES; BINARY ALLOY SYSTEMS; CRYSTAL GROWTH; FCC LATTICES; FERROMAGNETIC MATERIALS; ION BEAMS; IRON ALLOYS; KEV RANGE 100-1000; LATTICE PARAMETERS; MAGNETIC MOMENTS; MAGNETIC PROPERTIES; METALLIC GLASSES; METASTABLE STATES; MOLECULAR DYNAMICS METHOD; NANOSTRUCTURES; NIOBIUM ALLOYS; SIMULATION; XENON IONS

Citation Formats

Tai, K P, Dai, Y, and Liu, B X. Metastable phase formation and magnetic properties of the Fe-Nb system studied by atomistic modeling and ion beam mixing. United States: N. p., 2008. Web. doi:10.1063/1.2955716.
Tai, K P, Dai, Y, & Liu, B X. Metastable phase formation and magnetic properties of the Fe-Nb system studied by atomistic modeling and ion beam mixing. United States. doi:10.1063/1.2955716.
Tai, K P, Dai, Y, and Liu, B X. Tue . "Metastable phase formation and magnetic properties of the Fe-Nb system studied by atomistic modeling and ion beam mixing". United States. doi:10.1063/1.2955716.
@article{osti_21137393,
title = {Metastable phase formation and magnetic properties of the Fe-Nb system studied by atomistic modeling and ion beam mixing},
author = {Tai, K P and Dai, Y and Liu, B X},
abstractNote = {With the aid of ab initio calculations, an n-body Fe-Nb embedded-atom potential is first constructed and then applied to study the crystal-to-amorphous phase transition through molecular dynamic simulations. The simulations determine that the glass-forming range of the Fe-Nb system is 18-83 at. % of Nb. In ion beam mixing experiments, five Fe-Nb multilayered films with overall compositions of Fe{sub 85}Nb{sub 15}, Fe{sub 75}Nb{sub 25}, Fe{sub 55}Nb{sub 45}, Fe{sub 25}Nb{sub 75}, and Fe{sub 15}Nb{sub 85}, respectively, are irradiated by 200 keV xenon ions to doses in the range of (1-7)x10{sup 15}Xe{sup +}/cm{sup 2}. The result shows that the Fe-Nb metallic glasses can be synthesized within a composition range of 25-75 at. % of Nb, matching reasonably well the theoretical prediction. Moreover, in the Fe{sub 55}Nb{sub 45} sample, a fcc-structured alloy phase with a large lattice constant of a{approx_equal}0.408 nm was obtained at a dose of 3x10{sup 15} Xe{sup +}/cm{sup 2} and the associated magnetic moment per Fe atom was measured to be 2.41{mu}{sub B}. The observed magnetic moment is much greater than the initial value of 1.42{mu}{sub B} in the bcc-Fe lattice and can thus serve as evidence confirming the high-spin ferromagnetic state of fcc Fe predicted by ab initio calculations. Interestingly, further irradiation induced phase separation in the Fe{sub 55}Nb{sub 45} sample, i.e., irradiation to a dose of 5x10{sup 15} Xe{sup +}/cm{sup 2} results in the growth of a fractal pattern consisting of Fe{sub 72}Nb{sub 28} nanoclusters embedded in Fe{sub 35}Nb{sub 65} matrix. The formation mechanism of the metastable phases as well as that of the fractal pattern observed in the Fe-Nb system was discussed in terms of the atomic collision theory and the well-known cluster-diffusion-limited-aggregation model.},
doi = {10.1063/1.2955716},
journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 1,
volume = 104,
place = {United States},
year = {2008},
month = {7}
}