Abstract
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.
Highlights
12 March 2015Content from this work Abstract may be used under the A method to calculate the effective spin Hamiltonian for a transition metal impurity in a nonterms of the Creative Commons Attribution 3.0 magnetic insulating host is presented and applied to the paradigmatic case of Fe in MgO
Understanding the electronic properties of magnetic transition metals embedded in diamagnetic hosts plays a central role in several branches of condensed matter physics and materials science
Extraordinary progress in instrumentation techniques makes it possible to probe individual magnetic atoms in a solid state environment [4, 5] using a variety of techniques, such as scanning tunneling microscope (STM) inelastic electron spectroscopy (IETS) [6, 7], and single quantum dot photoluminescence [8, 9]
Summary
Content from this work Abstract may be used under the A method to calculate the effective spin Hamiltonian for a transition metal impurity in a nonterms of the Creative Commons Attribution 3.0 magnetic insulating host is presented and applied to the paradigmatic case of Fe in MgO. Step we calculate the electronic structure employing standard density functional theory (DFT), based. The corresponding attribution to the author(s) and the title of basis of atomic-like maximally localized Wannier functions is derived and used to represent the DFT the work, journal citation Hamiltonian, resulting in a tight-binding model for the atomic orbitals of the magnetic impurity. The low energy sector of this multi-electron Hamiltonian is mapped into effective spin models that, in addition to the spin matrices S, can include the orbital angular momentum L when appropriate.
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