Structural, magnetic and electronic properties of Cu-Fe nanoclusters by density functional theory calculations

Abstract

We present results from density functional theory calculations referring to the magnetic properties of 13, 55, 147 and 309 atoms Cu-Fe icosahedral nanoclusters. Aiming in finding the nanocluster with the optimum magnetic moment (μΒ) we explored the various sizes considering several compositions and atomic conformations. It came out that configurations with agglomerated Fe atoms inside the Cu-Fe nanoclusters and pure Cu surface shell are energetically favoured as demonstrated e.g. for the Cu49Fe6 with 2.3μΒ compared to 2.1μΒ of the Fe bcc. The highest magnetic moment, 3.6μΒ, was found in the Cu12Fe case with the Fe atom located at the surface cell, while 3.18μΒ was found for the Cu297Fe12 in a similar configuration having Fe atoms surrounded by Cu that occupy the surface shell's edges. The magnetic moment is mainly due to Fe's spin up - down electronic density of states difference close to the Fermi level (EF). In particular, the Spin-up Fe d electronic density of states are fully occupied yielding wavefunctions with homogeneous change distribution while the Spin-down is almost unoccupied exhibiting dangling bonding states close to EF. These results could be used for the design of environmental sustainable smart alloys with superior magnetic properties e.g. by depositing Fe or FeCu on Cu nanoclusters or including new elements that provide the possibility of keeping the Fe Spin up-down electronic occupation difference close to EF.