Shape-dependent magnetism of bimetallic FeNi nanosystems

Shape-dependent magnetic properties of a bimetallic system have been studied for FeNi nanoparticles with well-defined concave cubic and octahedron shapes. The alloy composition was chosen to be close to that of an Invar FeNi alloy (with 35% Ni content) but with the coexistence of both bcc and fcc phases, in order to investigate the role of phase combinations in controlling the magnetic properties for the first time. Different saturation magnetization and coercivities were observed for the resulting FeNi alloy nanoparticles, and these differences have been correlated with surface anisotropy and formation of different two-phase combinations. The role of two-phase combinations in governing the magnetic properties has also been studied for both bulk and nanoalloys by large-scale Density Function Theory (DFT) calculations using VASP, which provides a new complementary approach to understanding the magnetic properties of alloy materials.