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Title: Absence of Magnetism in Hcp Iron-Nickel at 11K

Abstract

Synchrotron Moessbauer spectroscopy (SMS) was performed on an hcp-phase alloy of composition Fe{sub 92}Ni{sub 8} at a pressure of 21 GPa and a temperature of 11 K. Density functional theoretical calculations predict antiferromagnetism in both hcp Fe and hcp Fe-Ni. For hcp Fe, these calculations predict no hyperfine magnetic field, consistent with previous experiments. For hcp Fe-Ni, however, substantial hyperfine magnetic fields are predicted, but these were not observed in the SMS spectra. Two possible explanations are suggested. First, small but significant errors in the generalized gradient approximation density functional may lead to an erroneous prediction of magnetic order or of erroneous hyperfine magnetic fields in antiferromagnetic hcp Fe-Ni. Alternately, quantum fluctuations with periods much shorter than the lifetime of the nuclear excited state would prohibit the detection of moments by SMS.

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930619
Report Number(s):
BNL-80939-2008-JA
Journal ID: ISSN 0031-9007; PRLTAO; TRN: US0901421
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 97
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ALLOYS; ANTIFERROMAGNETISM; APPROXIMATIONS; DETECTION; DENSITY FUNCTIONAL METHOD; EXCITED STATES; FLUCTUATIONS; IRON COMPOUNDS; LIFETIME; MAGNETIC FIELDS; MAGNETISM; MOESSBAUER EFFECT; SPECTROSCOPY; NICKEL COMPOUNDS; PRESSURE RANGE GIGA PA; SPECTRA; SYNCHROTRON RADIATION; TEMPERATURE RANGE 0000-0013 K; national synchrotron light source

Citation Formats

Papandrew,A., Lucas, M., Stevens, R., Halevy, I., Fultz, B., Hu, M., Chow, P., Cohen, R., and Somayazulu, M.. Absence of Magnetism in Hcp Iron-Nickel at 11K. United States: N. p., 2006. Web. doi:10.1103/PhysRevLett.97.087202.
Papandrew,A., Lucas, M., Stevens, R., Halevy, I., Fultz, B., Hu, M., Chow, P., Cohen, R., & Somayazulu, M.. Absence of Magnetism in Hcp Iron-Nickel at 11K. United States. doi:10.1103/PhysRevLett.97.087202.
Papandrew,A., Lucas, M., Stevens, R., Halevy, I., Fultz, B., Hu, M., Chow, P., Cohen, R., and Somayazulu, M.. Sun . "Absence of Magnetism in Hcp Iron-Nickel at 11K". United States. doi:10.1103/PhysRevLett.97.087202.
@article{osti_930619,
title = {Absence of Magnetism in Hcp Iron-Nickel at 11K},
author = {Papandrew,A. and Lucas, M. and Stevens, R. and Halevy, I. and Fultz, B. and Hu, M. and Chow, P. and Cohen, R. and Somayazulu, M.},
abstractNote = {Synchrotron Moessbauer spectroscopy (SMS) was performed on an hcp-phase alloy of composition Fe{sub 92}Ni{sub 8} at a pressure of 21 GPa and a temperature of 11 K. Density functional theoretical calculations predict antiferromagnetism in both hcp Fe and hcp Fe-Ni. For hcp Fe, these calculations predict no hyperfine magnetic field, consistent with previous experiments. For hcp Fe-Ni, however, substantial hyperfine magnetic fields are predicted, but these were not observed in the SMS spectra. Two possible explanations are suggested. First, small but significant errors in the generalized gradient approximation density functional may lead to an erroneous prediction of magnetic order or of erroneous hyperfine magnetic fields in antiferromagnetic hcp Fe-Ni. Alternately, quantum fluctuations with periods much shorter than the lifetime of the nuclear excited state would prohibit the detection of moments by SMS.},
doi = {10.1103/PhysRevLett.97.087202},
journal = {Physical Review Letters},
number = ,
volume = 97,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • Synchrotron Moessbauer spectroscopy (SMS) was performed on an hcp-phase alloy of composition Fe{sub 92}Ni{sub 8} at a pressure of 21 GPa and a temperature of 11 K. Density functional theoretical calculations predict antiferromagnetism in both hcp Fe and hcp Fe-Ni. For hcp Fe, these calculations predict no hyperfine magnetic field, consistent with previous experiments. For hcp Fe-Ni, however, substantial hyperfine magnetic fields are predicted, but these were not observed in the SMS spectra. Two possible explanations are suggested. First, small but significant errors in the generalized gradient approximation density functional may lead to an erroneous prediction of magnetic order ormore » of erroneous hyperfine magnetic fields in antiferromagnetic hcp Fe-Ni. Alternately, quantum fluctuations with periods much shorter than the lifetime of the nuclear excited state would prohibit the detection of moments by SMS.« less
  • Resistance to swelling under irradiation and a low rate of corrosion in high temperature environments make Fe-Cr and Fe-Cr-Ni alloys promising structural materials for energy technologies. In this paper we report the results obtained using a combination of density functional theory (DFT) techniques: plane wave basis set solutions for pseudo-potentials and multiple scattering solutions for all electron potentials. We have found a very strong role of magnetism in the stability of screw dislocation cores in pure Fe and their interaction with Cr and Ni magnetic impurities. In particular, the screw dislocation quadrupole in Fe is stabilized only in the presencemore » of ferromagnetism. In addition, Ni atoms, who's magnetic moment is oriented along the magnetization direction of the Fe matrix, prefer to occupy in core positions whereas Cr atoms, which couple anti-ferromagnetically with the Fe matrix, prefer out of the dislocation core positions. In effect, Ni impurities are attracted to, while Cr impurities are repelled by the dislocation core. Moreover, we demonstrate that this contrasting behavior can be explained only by the nature of magnetic coupling of the impurities to the Fe matrix. In addition, Cr interaction with the dislocation core mirrors that of Ni if the Cr magnetic moment is constrained to be along the direction of Fe matrix magnetization. In addition, we have shown that the magnetic contribution can affect the impurity-impurity interaction at distances up to a few Burgers vectors. In particular, the distance between Cr atoms in Fe matrix should be at least 3–4 lattice parameters in order to eliminate finite size effects.« less
  • We conducted high-pressure experiments on hexagonal close packed iron (hcp-Fe) in MgO, NaCl, and Ne pressure-transmitting media and found general agreement among the experimental data at 300 K that yield the best fitted values of the bulk modulus K 0 = 172.7(±1.4) GPa and its pressure derivative K 0'= 4.79(±0.05) for hcp-Fe, using the third-order Birch-Murnaghan equation of state. Using the derived thermal pressures for hcp-Fe up to 100 GPa and 1800 K and previous shockwave Hugoniot data, we developed a thermal equation of state of hcp-Fe. The thermal equation of state of hcp-Fe is further used to calculate themore » densities of iron along adiabatic geotherms to define the density deficit of the inner core, which serves as the basis for developing quantitative composition models of the Earth's inner core. We determine the density deficit at the inner core boundary to be 3.6%, assuming an inner core boundary temperature of 6000 K.« less