skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Phonons and elasticity of cementite through the Curie temperature

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1344572
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review B; Journal Volume: 95; Journal Issue: 2
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Mauger, L., Herriman, J. E., Hellman, O., Tracy, S. J., Lucas, M. S., Muñoz, J. A., Xiao, Yuming, Li, J., and Fultz, B.. Phonons and elasticity of cementite through the Curie temperature. United States: N. p., 2017. Web. doi:10.1103/PhysRevB.95.024308.
Mauger, L., Herriman, J. E., Hellman, O., Tracy, S. J., Lucas, M. S., Muñoz, J. A., Xiao, Yuming, Li, J., & Fultz, B.. Phonons and elasticity of cementite through the Curie temperature. United States. doi:10.1103/PhysRevB.95.024308.
Mauger, L., Herriman, J. E., Hellman, O., Tracy, S. J., Lucas, M. S., Muñoz, J. A., Xiao, Yuming, Li, J., and Fultz, B.. Sun . "Phonons and elasticity of cementite through the Curie temperature". United States. doi:10.1103/PhysRevB.95.024308.
@article{osti_1344572,
title = {Phonons and elasticity of cementite through the Curie temperature},
author = {Mauger, L. and Herriman, J. E. and Hellman, O. and Tracy, S. J. and Lucas, M. S. and Muñoz, J. A. and Xiao, Yuming and Li, J. and Fultz, B.},
abstractNote = {},
doi = {10.1103/PhysRevB.95.024308},
journal = {Physical Review B},
number = 2,
volume = 95,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2017},
month = {Sun Jan 01 00:00:00 EST 2017}
}
  • In structurally ordered magnetic thin films, the Curie temperature (TC) of ferromagnetic films depends on the exchange integral of the short range ordered neighboring atoms. The exchange integral may be adjusted by controlling elemental substitutional concentration at the lattice site of interest. We show how to control the TC in high anisotropy L10 Fe50Pt50 magnetic thin films by substituting Rh into the Pt site. Rh substitution in L10 FePt modified the local atomic environment and corresponding electronic properties while retaining the ordered L10 phase. The analysis of extended x-ray Absorption Fine Structure (EXAFS) spectra shows that Rh uniformly substitutes formore » Pt in L10 FePt. With 15 at. % of Rh substitution, temperature-dependent magnetic measurements show that the saturation magnetization (Ms) decreases from 1152 emu/cc to 670 emu/cc, the magnetocrystalline anisotropy (Ku) drops from 5×107 erg/cc to 2×107 erg/cc, and TC decreased from 750 to 500 K. A model of antiferromagnetic (AFM) defects caused by controlled Rh substitution of the Pt site, reducing the TC, is proposed to interpret this phenomenon and the validity is further examined by ab initio density functional calculations.« less
  • In structurally ordered magnetic thin films, the Curie temperature (T{sub C}) of ferromagnetic films depends on the exchange integral of the short range ordered neighboring atoms. The exchange integral may be adjusted by controlling the elemental substitutional concentration at the lattice site of interest. We show how to control the T{sub C} in high anisotropy L1{sub 0} Fe{sub 50}Pt{sub 50} magnetic thin films by substituting Rh into the Pt site. Rh substitution in L1{sub 0} FePt modified the local atomic environment and the corresponding electronic properties, while retaining the ordered L1{sub 0} phase. The analysis of extended x-ray Absorption Finemore » Structure spectra shows that Rh uniformly substitutes for Pt in L1{sub 0} FePt. A model of antiferromagnetic defects caused by controlled Rh substitution of the Pt site, reducing the T{sub C,} is proposed to interpret this phenomenon and its validity is further examined by ab initio density functional calculations.« less
  • The structure and behavior of the cementite phase has a profound effect on the properties of steels and cast irons. For example, the size and distribution of cementite particles is known to influence the fracture and fatigue behavior of steels. Cementite plays a critical role in various phase transformations in the system, for example the pearlite and bainite reactions. Recently, it has been shown that cementite plays an important role in the process of austenite formation which occurs when the eutectoid temperature is exceeded. Despite the importance of the cementite phase in the context of ferrous metallurgy, it appears thatmore » little emphasis has been placed on determining the dependence of the lattice parameters on temperature. The results which are available have been determined using X-ray diffractometry, which can be subject to systematic errors arising from (i) specimen height misalignments, and (ii) temperature inhomogeneities. The purpose of the present paper is to report data from a high purity Fe-C hypereutectoid steel, which were obtained using high-resolution neutron diffractometry. The cementite is thus in equilibrium with the matrix phase, even above the eutectoid temperature, and this allows measurements to be obtained with a considerable degree of precision.« less
  • Deciphering the origin of seismic heterogeneity has been one of the major challenges in understanding the geochemistry and geodynamics of the deep mantle. Fully anisotropic elastic properties of constituent minerals at relevant pressure-temperature conditions of the lower mantle can be used to calculate seismic heterogeneity parameters in order to better understand chemically and thermally induced seismic heterogeneities. In this study, the single-crystal elastic properties of ferropericlase (Mg0.94Fe0.06)O were measured using Brillouin spectroscopy and X-ray diffraction at conditions up to 50 GPa and 900 K. The velocity-density results were modeled using third-order finite-strain theory and thermoelastic equations along a representative geothermmore » to investigate high pressure-temperature and compositional effects on the seismic heterogeneity parameters. Our results demonstrate that from 660 to 2000 km, compressional wave anisotropy of ferropericlase increased from 4% to 9.7%, while shear wave anisotropy increased from 9% to as high as 22.5%. The thermally induced lateral heterogeneity ratio (RS/P = ∂lnVS/∂lnVP) of ferropericlase was calculated to be 1.48 at ambient pressure but decreased to 1.43 at 40 GPa along a representative geotherm. The RS/P of a simplified pyrolite model consisting of 80% bridgmanite and 20% ferropericlase was approximately 1.5, consistent with seismic models at depths from 670 to 1500 km, but showed an increased mismatch at lower mantle depths below ~1500 km. This discrepancy below mid-lower mantle could be due to either a contribution from chemically induced heterogeneity or the effects of the Fe spin transition in the deeper parts of the Earth's lower mantle.« less