2 research outputs found
Strain-induced structural instability in FeRh
We perform density functional calculations to investigate the structure of
the inter-metallic alloy FeRh under epitaxial strain. Bulk FeRh exhibits a
metamagnetic transition from a low-temperature antiferromagnetic (AFM) phase to
a ferromagnetic (FM) phase at 350K, and its strain dependence is of interest
for tuning the transition temperature to the room-temperature operating
conditions of typical memory devices. We find an unusually strong dependence of
the structural energetics on the choice of exchange-correlation functional,
with the usual local density approximation (LDA) yielding the wrong
ground-state structure, and generalized gradient (GGA) extensions being in
better agreement with the bulk experimental structure. Using the GGA we show
the existence of a metastable face-centered-cubic (fcc)-like AFM structure that
is reached from the ground state body-centered-cubic (bcc) AFM structure by
following the epitaxial Bain path. We predict that this metastable fcc-like
structure has a significantly higher conductivity than the bcc AFM phase. We
show that the behavior is well described using non-linear elasticity theory,
which captures the softening and eventual sign change of the orthorhombic shear
modulus under compressive strain, consistent with this structural instability.
Finally, we predict the existence of an additional unit-cell-doubling lattice
instability, which should be observable at low temperature.Comment: 10 pages, 7 figure