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arXiv · 1710.04199

FeRh groundstate and martensitic transformation

Nikolai A. Zarkevich·Duane D. Johnson
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Abstract

Cubic B2 FeRh exhibits a metamagnetic transition [(111) antiferromagnet (AFM) to ferromagnet (FM)] around 353 K and remains structurally stable at higher temperatures. However, the calculated zero-Kelvin phonons of AFM FeRh exhibit imaginary modes at M-points in the Brillouin zone, indicating a premartensitic instability, which is a precursor to a martensitic transformation at low temperatures. Combining electronic-structure calculations with ab initio molecular dynamics, conjugate gradient relaxation, and the solid-state nudged-elastic band (SSNEB) methods, we predict that AFM B2 FeRh becomes unstable at ambient pressure and transforms without a barrier to an AFM(111) orthorhombic (martensitic) groundstate below 90K. We also consider competing structures, in particular, a tetragonal AFM(100) phase that is not the global groundstate, as proposed [Phys. Rev. B 94, 180407(R) (2016)], but a constrained solution.

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Nikolai A. Zarkevich, Duane D. Johnson. 2017-11-25. FeRh groundstate and martensitic transformation. https://doi.org/10.1103/physrevb.97.014202

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