A relativistic treatment of interacting spin-aligned electron systems: application to ferromagnetic iron, nickel and palladium metal

Current-Driven Magnetization Reversal in Orbital Chern Insulators

Graphene multilayers with flat moiré minibands can exhibit the quantized anomalous Hall effect due to the combined influence of spontaneous valley polarization and topologically nontrivial valley-projected bands. The sign of the Hall effect in these Chern insulators can be reversed either by applying an external magnetic field, or by driving a transport current through the system. We propose a current-driven mechanism whereby reversal occurs along lines in the (current I, magnetic-field B) control parameter space with slope dI/dB=(e/h)MA_{M}(1-γ^{2})/γ, where M is the magnetization, A_{M} is the moiré unit cell area, and γ<1 is the ratio of the chemical potential difference between valleys along a domain wall to the electrical bias eV.

Anomalous transport and possible phase transition in palladium nanojunctions

Many phenomena in condensed matter are thought to result from competition between different ordered phases. Palladium is a paramagnetic metal close to both ferromagnetism and superconductivity and is, therefore, a potentially interesting material to consider. Nanoscale structuring of matter can modify relevant physical energy scales, leading to effects such as locally modified magnetic interactions. We present transport measurements in electromigrated palladium break junction devices showing the emergence at low temperatures of anomalous sharp features in the differential conductance. These features appear symmetrically in applied bias and exhibit a temperature dependence of their characteristic voltages reminiscent of a mean-field phase transition. The systematic variation of these voltages with zero bias conductance, together with density functional theory calculations illustrating the relationship between the magnetization of Pd and atomic coordination, suggests that the features may result from the onset of spontaneous magnetization in the nanojunction electrodes. We propose that the characteristic conductance features are related to inelastic tunneling involving magnetic excitations.

Enhanced magnetic moment in Fe-doped Pd(n) clusters (n = 1-13): a density functional study

Here we report a systematic theoretical study of the equilibrium structures, electronic and magnetic properties of FePd(n-1) clusters with n = 1-13, within the framework of density functional theory. The results show that the doping of a single Fe impurity enhances the binding energies as well as the magnetic moment of the Pd(n) clusters. Interestingly, in the mid-size region (n = 5-7), Fe substitution in Pd(n) clusters results in a three fold enhancement in the magnetic moment. We find that the geometries of the host clusters do not change significantly after the addition of an Fe atom, except for n = 6, 7, 11, 12. In the lowest energy configurations, the Fe atom tries to increase its coordination number by moving from the convex to the interior site as the number of Pd atoms varies from 2 to 12.

Electronic structure and magnetic properties of solids

We review basic computational techniques for simulations of various magnetic properties of solids. Several applications to compute magnetic anisotropy energy, spin wave spectra, magnetic susceptibilities and temperature dependent magnetisations for a number of real systems are presented for illustrative purposes.

Importance of correlation effects on magnetic anisotropy in Fe and Ni

We calculate magnetic anisotropy energy of Fe and Ni by taking into account the effects of strong electronic correlations, spin-orbit coupling, and noncollinearity of intra-atomic magnetization. The LDA+U method is used and its equivalence to dynamical mean-field theory in the static limit is emphasized. Both experimental magnitude of magnetic anisotropy energy and direction of magnetization are predicted correctly near U = 1.9 eV, J = 1.2 eV for Ni and U = 1.2 eV, J = 0.8 eV for Fe. Correlations modify the one-electron spectra which are now in better agreement with experiments.