Conductance of single-atom magnetic junctions: A first-principles study

Abstract

We present a first-principles investigation to show that the contact conductance of a half conductance quantum ($G_0/2$) found previously does not generally hold for single-atom magnetic junctions composed of a tip and an adatom dsorbed on a surface. The contact conductance of the Ni-Co/Co(111) junction is approximately $G_0/2$, while for the Co-Co/Co(111), Ni-Ni/Ni(111), and Ni-Ni/Ni(001) junctions the contact conductances are 0.80$G_0$, 1.55$G_0$, and 1.77$G_0$, respectively. The deviation from $G_0/2$ is mainly caused by the variation of the spin-down conductance largely determined by the minority $d$ orbitals, as the spin-up one changes little for different junctions.Comment: 4 pages, 4 figure

Conductance of ferro- and antiferro-magnetic single-atom contacts: A first-principles study

“…. We note that the present result is consistent with our previous theoretical finding: For SAMJs with similar atomic geometry but different species, their spin-down conductance is sensitive to the species while the spin-up one is not [11]. In Fig.…”

“…For the Ni-X/Ni(001) junctions, the same trend also exists (see Fig.2(c) vs. (d)). We note that the present result is consistent with our previous theoretical finding: For SAMJs with similar atomic geometry but different species, their spin-down conductance is sensitive to the species while the spin-up one is not [11]. In Fig.2, we can also find that for the Ni-Fe/Ni(001) junction the spin-up conductance is greater than the spin-down one, while for the other junctions the spin-down conductance becomes larger.…”

“…In transport calculations, these atoms construct the scattering region, and four additional (001) layers are added at the two ends of the scattering region, respectively, to mimic the left and right electrodes (leads). This kind of structure model has been proven to be reasonable in describing the spin transport properties of SAMJs in a previous work [11].…”

“…A numerical double zeta plus polarization basis set (DZP) is used for the wavefunction expansion. Other computational details are the same as adopted in our previous work [11]. The spin-polarization ratio (SPR) at Fermi energy is defined as P = (T ↑ − T ↓ )/(T ↑ + T ↓ ), where T ↑ and T ↓ denote the transmission coefficient of the majority and minority spin, respectively.…”