The phonon softening due to melting of the ferromagnetic order in elemental iron
ORAL
Abstract
We study the fundamental question of the lattice dynamics of a metallic ferromagnet in the regime where the static long range magnetic order is replaced by the fluctuating local moments embedded in a metallic host.
We use the \textit{ab initio} Density Functional Theory(DFT)+embedded Dynamical Mean-Field Theory(eDMFT) functional approach,
to address the dynamic stability of iron polymorphs and the phonon softening with increased temperature.
We show that the non-harmonic and inhomogeneous phonon softening measured in iron is a result of the melting of the long range ferromagnetic order, and is unrelated to the first order structural transition from the BCC to the FCC phase, as is usually assumed. We predict that the BCC structure is dynamically stable at all temperatures at normal pressure, and is only thermodynamically unstable between the BCC-$\alpha$ and the BCC-$\delta$ phase of iron.
We use the \textit{ab initio} Density Functional Theory(DFT)+embedded Dynamical Mean-Field Theory(eDMFT) functional approach,
to address the dynamic stability of iron polymorphs and the phonon softening with increased temperature.
We show that the non-harmonic and inhomogeneous phonon softening measured in iron is a result of the melting of the long range ferromagnetic order, and is unrelated to the first order structural transition from the BCC to the FCC phase, as is usually assumed. We predict that the BCC structure is dynamically stable at all temperatures at normal pressure, and is only thermodynamically unstable between the BCC-$\alpha$ and the BCC-$\delta$ phase of iron.
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Presenters
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Qiang Han
Rutgers Univ, Rutgers University
Authors
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Qiang Han
Rutgers Univ, Rutgers University
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Turan Birol
Chemical Engineering and Materials Science, University of Minnesota, Chemical Engineering and Material Science, University of Minnesota, CEMS, University of Minnesota, Department of chemical engineering and materials science,University of Minnesota, Department of Chemical Engineering and Materials Science, University of Minnesota, Univ of Minnesota - Twin Cities, Chemical Engineering and Materials Science, university of minnesota
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Kristjan Haule
Physics and Astronomy, Rutgers Univ, Dept of Physics and Astronomy, Rutgers Univ, Rutgers Univ, Rutgers University