Effect of Pd alloying on structural, electronic and magnetic properties of L10Fe-Ni.

We present a systematic study of the effect of Pd-alloying on phase stability, electronic structure, and elastic properties in L1$_{0}$ Fe-Ni using density-functional theory. Being from the same group of the periodic table, Pd is the best candidate for chemical alloying . The Fe-Ni/Fe-Pd/Ni-Pd bond-length increases with increasing Pd-concentration, which weakens the hybridization between low lying energy states below Fermi-level. The reduced hybridization decreases the relative thermodynamic stability of L1$_{0}$ Fe(Ni$_{1-x}$Pd$_{x}$) until $x$=0.75. Beyond this concentration, the relative stability gets enhanced, which is attributed to a unique change in the lattice distortion (c/a). The elastic properties show a non-monotonous behavior as a function of $x$, which is again due to a specific change-over in the uniaxial strain. We found that Pd alloying increases the local Fe moment and structural anisotropy of L1$_{0}$ FeNi, which are important for applications such as microwave absorption, refrigeration systems, recording devices, imaging and sensors. We believe that the present study for the chemical alloying effect can provide critical insights towards the understanding of electronic-structure and elastic behavior of other technologically important materials.