Molecular dynamics simulation of the formation of Cu-Pt nanocontacts in the mechanically controlled break junction experiments.

The formation of the Cu-Pt nanocontacts has been investigated by means of classical molecular dynamics simulations. The simulations of the mechanically controlled break junction experiment have been performed in wide ranges of temperatures (0-300 K) and at relative Pt concentrations (0-20%). The structure of the breaking area has been studied 2 ns before the final breaking of the nanocontacts. The length of the breaking area increases with the increase of the temperature and decreases with the increase of the relative Pt concentration. The structure of the breaking area has been investigated by means of the radial distribution function method. The breaking area usually has one of the following structures: (i) a bulk-like structure, (ii) a structure consisting of centered icosahedrons rotated 90°, or (iii) an icosahedral structure composed of pentagonal rings. The structure of the breaking area is almost independent of the temperature and the stretching direction due to the strong Cu-Pt interaction.

Emergence of spin-filter states in Pt-Fe nanowires.

Our theoretical study predicts the emergence of a new spin-filter state in one-dimensional Pt-Fe bimetallic nanowires. The results show the existence of two transmission states in contracted "zig-zag" Pt-Fe nanowires with low and high transmission 1G0 and 3G0, correspondingly, and one transmission state in linear stretched nanowires with conductance 2G0. Our first principle calculations revealed the dependence of quantum conductance of Pt-Fe nanowires on their geometry and atomic structure. Thus we found that nanowire stretching up to the interatomic distance of 2.3 Å leads to the transition of the wire from a "zig-zag" to the linear configuration, leading to changes in the conductance properties of the wire, i.e. formation of a new spin-filter state. Our study shows also the emergence of a magnetic transition from ferromagnetic to antiferromagnetic states under wire stretching. We found that the spin-filter state exists only in "zig-zag" Pt-Fe nanowires in the ferromagnetic state. Moreover, the spin-polarization of quantum electron transport through Pt-Fe nanowires vanishes totally in linear stretched nanowires in an antiferromagnetic state. Our electronic structure calculation reveals the emergence of new hybridized states in the band structure of the Pt-Fe nanowire, which causes the formation of a new spin-filter state.

Magnetic properties of Pd atomic chains formed during submonolayer deposition of 3d metals on Pd(110).

Recently, an unusual intermixing-driven scenario for the growth of atomic Pd chains on a Pd(110) surface during deposition of 3d metal atoms has been predicted (Stepanyuk 2009 Phys. Rev. B 79 155410) and confirmed by STM and STS experiments (Wie et al 2009 Phys. Rev. Lett. 103 225504). Performing ab initio calculations we demonstrate that Pd atomic chains grown above embedded Fe atoms exhibit magnetic properties which depend on the substrate mediated exchange interaction between the Fe atoms.