Magnetism of two-dimensional defects in Pd: stacking faults, twin boundaries and surfaces

TL;DR

This study uses first-principles calculations to show that two-dimensional stacking defects and surface orientations in Pd can induce or enhance ferromagnetism, contrasting with the paramagnetic bulk face-centered cubic phase.

Contribution

It reveals that local stacking variations and surface orientations in Pd significantly influence its magnetic properties, highlighting the role of defects and surfaces in nanoscale magnetism.

Findings

Hexagonal close-packed Pd is ferromagnetic with 0.35 μB/atom.

Stacking faults and twin boundaries increase magnetic susceptibility.

(111) surface enhances ferromagnetism, while (100) surface reduces it.

Abstract

Careful first-principles density functional calculations reveal the importance of hexagonal versus cubic stacking of closed packed planes of Pd as far as local magnetic properties are concerned. We find that, contrary to the stable face centered cubic phase, which is paramagnetic, the hexagonal close-packed phase of Pd is ferromagnetic with a magnetic moment of 0.35 $\mu_{B}$/atom. Our results show that two-dimensional defects with local hcp stacking, like twin boundaries and stacking faults, in the otherwise fcc Pd structure, increase the magnetic susceptibility. The (111) surface also increases the magnetic susceptibility and it becomes ferromagnetic in combination with an individual stacking fault or twin boundary close to it. On the contrary, we find that the (100) surface decreases the tendency to ferromagnetism. The results are consistent with the magnetic moment recently observed in small Pd nanoparticles, with a large surface area and a high concentration of two-dimensional stacking defects.