Spin-orbit effect and magnetic anisotropy in Pt clusters

Based on the non-collinear (NCL) and spinorbit coupling (SOC) implementation of the density-functional theory (DFT) calculations, isomeric structures, spin and orbital moments, magnetic anisotropies, as well as magnetic anisotropy energy (MAE) are investigated for Pt-n clusters (n=28, 13). Our studies show that the planar structures are superior to the three-dimensional structures in stabilizing Pt clusters up to n=7, favored by both scalar relativistic calculations and SOC calculations. For each cluster size, relative stabilities of different low-lying energy isomers are not alternated by the SOC effects. Strong magnetic anisotropies and remarkable orbital moments (0.1-0.4 mu(B/)atom) are found in Pt clusters. The easy axes usually prefer the orientations that are in the basal planes of the structures and parallel to the principal axes of symmetry. There is always collinearity between total spin moments and total orbital moments, favoring a strict ferromagnetic coupling. It is revealed that small Pt clusters mostly exhibit large MAEs. (C) 2012 Elsevier B.V. All rights reserved.