Derivation of the spin Hamiltonians for Fe in MgO

A method to calculate the effective spin Hamiltonian for a transition metal impurity in a non-magnetic insulating host is presented and applied to the paradigmatic case of Fe in MgO. In the first step we calculate the electronic structure employing standard density functional theory (DFT), based on generalized gradient approximation (GGA), using plane waves as a basis set. The corresponding basis of atomic-like maximally localized Wannier functions is derived and used to represent the DFT Hamiltonian, resulting in a tight-binding model for the atomic orbitals of the magnetic impurity. The third step is to solve, by exact numerical diagonalization, the N electron problem in the open shell of the magnetic atom, including both effects of spin–orbit and Coulomb repulsion. Finally, the low energy sector of this multi-electron Hamiltonian is mapped into effective spin models that, in addition to the spin matrices S, can also include the orbital angular momentum L when appropriate. We successfully apply the method to Fe in MgO, considering both the undistorted and Jahn–Teller (JT) distorted cases. Implications for the influence of Fe impurities on the performance of magnetic tunnel junctions based on MgO are discussed.

Controlled Complete Suppression of Single-Atom Inelastic Spin and Orbital Cotunneling

The inelastic portion of the tunnel current through an individual magnetic atom grants unique access to read out and change the atom’s spin state, but it also provides a path for spontaneous relaxation and decoherence. Controlled closure of the inelastic channel would allow for the latter to be switched off at will, paving the way to coherent spin manipulation in single atoms. Here, we demonstrate complete closure of the inelastic channels for both spin and orbital transitions due to a controlled geometric modification of the atom’s environment, using scanning tunneling microscopy (STM). The observed suppression of the excitation signal, which occurs for Co atoms assembled into chains on a Cu2N substrate, indicates a structural transition affecting the dz2 orbital, effectively cutting off the STM tip from the spin-flip cotunneling path.

Topological spin waves in the atomic-scale magnetic skyrmion crystal

We study the spin waves of the triangular skyrmion crystal that emerges in a two-dimensional spin lattice model as a result of the competition between Heisenberg exchange, Dzyalonshinkii–Moriya interactions, Zeeman coupling and uniaxial anisotropy. The calculated spin wave bands have a finite Berry curvature that, in some cases, leads to non-zero Chern numbers, making this system topologically distinct from conventional magnonic systems. We compute the edge spin-waves, expected from the bulk-boundary correspondence principle, and show that they are chiral, which makes them immune to elastic backscattering. Our results illustrate how topological phases can occur in self-generated emergent superlattices at the mesoscale.

Diplomatic Spin: EU3+3 talks on Iran’s nuclear file. CEPS Commentary, 21 November 2014

The Joint Plan of Action agreed upon with Iran on 24 November 2013 gave negotiators one year to forge a comprehensive agreement that restricts the country’s ability to militarise its nuclear programme. That deadline will lapse in the next few days and diplomats involved in the talks have been trying to rein in expectations that a deal will be struck on time. Satisfying domestic constituencies in Iran and the US is what makes the politics of dealing with the nuclear file so much harder than the physics of slowing down the nuclear programme. Any future deal will have to stand on its own merits, enabling Iran and the EU3+3 to cooperate on the other geopolitical challenges they face. Both parties should therefore balance their demands with what they can realistically offer and make concessions to reach a compromise. The author of this CEPS Commentary argues that if no deal is reached on November 24th, then diplomacy should be allowed to keep on spinning for a few more months.

Spin dependence of slow neutron scattering by deuterons /

Work performed at the Argonne National Laboratory.

Effects of stray magnetic fields and RF coupler asymmetry in the two-mile accelerator with sector focusing /

"AEC Contract AT(04-3)-400."

The dynamics of fields of higher spin /

Mode of access: Internet.

G-factor and donor spin-lattice relaxation for electrons in germanium and silicon.

"This group report is based on an article submitted to the Physical review."

Sportsman's digest of spin-fishing /

Includes index.

Organizational maintenance manual (including repair parts and special tools lists) : 2.75-inch low spin, folding fin aircraft rockets, 66-mm light antitank weapon systems, 3.5-inch rockets, and M3A2E1 rocket motor (JATO).

"June 1973."

Direct support and general support maintenance manual (including repair parts and special tools list) for 2.75-inch low spin, folding fin aircraft rockets, 66-mm light antitank weapon systems, 3.5-inch rockets and M3A2E1 rocket motor (JATO).

"August 1974."