Phonon densities of states of face-centered-cubic Ni-Fe alloys

Lucas, M. S.; Mauger, L.; Muñoz, J. A.; Halevy, I.; Horwath, J.; Semiatin, S. L.; Leontsev, S. O.; Stone, M. B.; Abernathy, D. L.; Xiao, Yuming; Chow, Paul; Fultz, B.

doi:10.1063/1.4794354

Cited by 14 publications

(11 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figure 5 compares our heat capacities with those found in the literature. Our measured heat capacity for the control sample is similar to the heat capacity measured on fcc Ni [73] and in good agreement with the heat capacity of A complete L1 2 ordering transition in this material would reduce the heat capacity by approximately 0.1 k B /atom (0.8 J/mol K) at 300 K [44], with most of this from phonons [67]. However, the L1 2 ordering in Ni 3 Fe is very sluggish.…”

Section: B Heat Capacitysupporting

confidence: 84%

“…There is evidence for some L1 2 chemical order in a few of the annealed control samples, seen as superlattice peaks in the XRD pattern. This, however, should not alter the phonon DOS significantly [44,66,67]. Other control samples did not show this L1 2 chemical order and all control samples gave very similar curves of C p (T ) as shown below in Fig.…”

Section: A Materialsmentioning

confidence: 69%

See 1 more Smart Citation

Thermodynamic stability and contributions to the Gibbs free energy of nanocrystalline Ni3Fe

Lohaus

Johnson

Ahnn

et al. 2020

Phys. Rev. Materials

View full text Add to dashboard Cite

The heat capacities of nanocrystalline Ni 3 Fe and control materials with larger crystallites were measured from 0.4-300 K. The heat capacities were integrated to obtain the enthalpy, entropy, and Gibbs free energy and to quantify how these thermodynamic functions are altered by nanocrystallinity. From the phonon density of states (DOS) measured by inelastic neutron scattering, we find that the Gibbs free energy is dominated by phonons and that the larger heat capacity of the nanomaterial below 100 K is attributable to its enhanced phonon DOS at low energies. Besides electronic and magnetic contributions, the nanocrystalline material has an additional contribution at higher temperatures, consistent with phonon anharmonicity. The nanocrystalline material shows a stronger increase with temperature of both the enthalpy and entropy compared to the bulk sample. Its entropy exceeds that of the bulk material by 0.4 k B /atom at 300 K. This is insufficient to overcome the enthalpy of grain boundaries and defects in the nanocrystalline material, making it thermodynamically unstable with respect to the bulk control material.

show abstract

Section: B Heat Capacitysupporting

confidence: 84%

Section: A Materialsmentioning

confidence: 69%

Thermodynamic stability and contributions to the Gibbs free energy of nanocrystalline Ni3Fe

Lohaus

Johnson

Ahnn

et al. 2020

Phys. Rev. Materials

View full text Add to dashboard Cite

show abstract

“…Recently, Lucas et al [54] obtained the partial phonon densities of states (DOS) of Fe and Ni, defined as the contribution from the given species to the total phonon DOS, at 300 K in fcc Fe-Ni samples through inelastic neutron scattering and nuclear resonant inelastic x-ray scattering. The experimentally derived partial and total vibrational entropies are compared to the DFT values in Fig.…”

Section: A Vibrational Entropymentioning

confidence: 99%

Ground-state properties and lattice-vibration effects of disordered Fe-Ni systems for phase stability predictions

2020

Phys. Rev. Materials

View full text Add to dashboard Cite

By means of density functional theory, we perform a focused study of both body-centered-cubic (bcc) and face-centered-cubic (fcc) Fe-Ni random solid solutions, represented by special quasirandom structures. The whole concentration range and various magnetic configurations are considered. Excellent agreement on the concentration dependence of magnetization is found between our results and experimental data, except in the Invar region. Some locally antiferromagnetic fcc structures are proposed to approach experimental values of magnetization. Vibrational entropies of ordered and disordered systems are calculated for various concentrations, showing an overall good agreement with available experimental data. The vibrational entropy systematically contributes to stabilize disordered rather than ordered structures and is not negligible compared to the configurational entropy. Free energy of mixing is estimated by including the vibrational and ideal configurational entropies. From them, low-and intermediate-temperature Fe-Ni phase diagrams are constructed, showing a better agreement with experimental data than the one from a recent thermodynamic assessment for some phase boundaries below 700 K. The determined order-disorder transition temperatures for the L1 0 and L1 2 phases are in good agreement with the experimental values, suggesting an important contribution of vibrational entropy.

show abstract

“… is the mean phonon energy and is very similar for different stoichiometries. We used the reported mean value of the phonon density of states in the iron nickel alloys meV measured with nuclear resonant inelastic x-ray scattering 34 . Following the Elliott-Yafet scenario, we assumed el-ph scattering as a driving mechanism for the spin relaxation.…”

Section: Resultsmentioning

confidence: 99%

Thresholding of the Elliott-Yafet spin-flip scattering in multi-sublattice magnets by the respective exchange energies

Born

Decker

Büchner

et al. 2021

Sci Rep

View full text Add to dashboard Cite

How different microscopic mechanisms of ultrafast spin dynamics coexist and interplay is not only relevant for the development of spintronics but also for the thorough description of physical systems out-of-equilibrium. In pure crystalline ferromagnets, one of the main microscopic mechanism of spin relaxation is the electron-phonon (el-ph) driven spin-flip, or Elliott-Yafet, scattering. Unexpectedly, recent experiments with ferro- and ferrimagnetic alloys have shown different dynamics for the different sublattices. These distinct sublattice dynamics are contradictory to the Elliott-Yafet scenario. In order to rationalize this discrepancy, it has been proposed that the intra- and intersublattice exchange interaction energies must be considered in the microscopic demagnetization mechanism, too. Here, using a temperature-dependent x-ray emission spectroscopy (XES) method, we address experimentally the element specific el-ph angular momentum transfer rates, responsible for the spin-flips in the respective (sub)lattices of Fe$$_{20}$$ 20 Ni$$_{80}$$ 80 , Fe$$_{50}$$ 50 Ni$$_{50}$$ 50 and pure nickel single crystals. We establish how the deduced rate evolution with the temperature is linked to the exchange coupling constants reported for different alloy stoichiometries and how sublattice exchange energies threshold the related el-ph spin-flip channels. Thus, these results evidence that the Elliott-Yafet spin-flip scattering, thresholded by sublattice exchange energies, is the relevant microscopic process to describe sublattice dynamics in alloys and elemental magnetic systems.

show abstract

Phonon densities of states of face-centered-cubic Ni-Fe alloys

Cited by 14 publications

References 18 publications

Thermodynamic stability and contributions to the Gibbs free energy of nanocrystalline Ni3Fe

Thermodynamic stability and contributions to the Gibbs free energy of nanocrystalline Ni3Fe

Ground-state properties and lattice-vibration effects of disordered Fe-Ni systems for phase stability predictions

Thresholding of the Elliott-Yafet spin-flip scattering in multi-sublattice magnets by the respective exchange energies

Contact Info

Product

Resources

About