Graphene as a Reversible Spin Manipulator of Molecular Magnets

Bhandary, Sumanta; Ghosh, Saurabh; Herper, Heike C.; Wende, Heiko; Eriksson, Olle; Sanyal, Biplab

doi:10.1103/physrevlett.107.257202

Cited by 73 publications

(62 citation statements)

References 23 publications

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“…Although the spin moment remains similar in all chemisorbed situations, a deformation in the spin density is expected to be quite high for a low-symmetry structures, leading to a large value of the spin dipole moment T z , 1 where T z is the expectation value of the z component of the spin-dipole operator T . Moreover spin densities differ due to different ligand fields exerted on FeP by different surfaces and their orientations.…”

Section: Spin Dipole Contributionmentioning

confidence: 99%

Manipulation of spin state of iron porphyrin by chemisorption on magnetic substrates

et al. 2013

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One of the key factors behind the rapid evolution of molecular spintronics is the efficient realization of spin manipulation of organic molecules with a magnetic center. The spin state of such molecules may depend crucially on the interaction with the substrate on which they are adsorbed. In this paper we demonstrate, using ab initio density functional calculations, that the stabilization of a high spin state of an iron porphyrin (FeP) molecule can be achieved via chemisorption on magnetic substrates of different species and orientations, viz., Co(001), Ni(001), Ni(110), and Ni(111). The signature of chemisorption of FeP on magnetic substrates is evident from broad features in N K x-ray absorption (XA) and Fe L 2,3 x-ray magnetic circular dichroism (XMCD) measurements. Our theoretical calculations show that the strong covalent interaction with the substrate increases Fe-N bond lengths in FeP and hence a switching to a high spin state (S = 2) from an intermediate spin state (S = 1) is achieved. Due to chemisorption, ferromagnetic exchange interaction is established through a direct exchange between Fe and substrate magnetic atoms as well as through an indirect exchange via the N atoms in FeP. The mechanism of exchange interaction is further analyzed by considering structural models constructed from ab initio calculations. Also, it is found that the exchange interaction between Fe in FeP and a Ni substrate is almost 4 times smaller than with a Co substrate. Finally, we illustrate the possibility of detecting a change in the molecular spin state by XMCD, Raman spectroscopy, and spin-polarized scanning tunneling microscopy.

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Section: Spin Dipole Contributionmentioning

confidence: 99%

Manipulation of spin state of iron porphyrin by chemisorption on magnetic substrates

et al. 2013

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“…This kind of spin transition produced by increasing inplane bond-lengths is feasible by depositing the complex on a substrate (graphene, polymers, etc.) and exerting a mechanical strain on the substrate [47].…”

Section: Ground State Changes and Magnetic Anisotropy Switchingmentioning

confidence: 99%

Mixed configuration ground state in iron(II) phthalocyanine

2015

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We calculate the angular dependence of the x-ray linear and circular dichroism at the L2,3 edges of α-Fe(II) Phthalocyanine (FePc) thin films using a ligand field model with full configuration interaction. We find the best agreement with the experimental spectra for a mixed ground state of 3 Eg(a ) with the two configurations coupled by the spin-orbit interaction. The 3 Eg(b) and 3 B2g states have an easy axis and plane anisotropies, respectively. Our model accounts for an easy-plane magnetic anisotropy and the measured magnitudes of the in-plane orbital and spin moments. The proximity in energy of the two configurations allows a switching of the magnetic anisotropy from easy plane to easy axis with a small change in the crystal field, as recently observed for FePc adsorbed on an oxidized Cu surface. We also discuss the possibility of a quintet ground state ( 5 A1g is 250 meV above the ground state) with planar anisotropy by manipulation of the Fe-C bond length by depositing the complex on a substrate that is subjected to a mechanical strain.

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“…In the present study, we focus on the occupation N ≈ 6, which corresponds to an Fe 2+ impurity, and consider a flat density of states for the bath. The Fe 2+ configuration is very abundant and occurs in various systems including metalorganic molecules like Fe-porpherine [21], Fe impurities embedded in topological insulators [22], and Fe-pnictide and Fe-chalcogenide superconductors [2]. Fe in noble metal hosts is expected to have a d-electron occupation between N = 6 and 7, which is likely closer to N = 6 than to N = 7 at least in the case of Fe on Ag surfaces [11].…”

Section: Introductionmentioning

confidence: 99%

Electronic excitation spectra of the five-orbital Anderson impurity model: From the atomic limit to itinerant atomic magnetism

Wehling

Werner

2014

Phys. Rev. B

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We study the competition of Coulomb interaction and hybridization effects in the five-orbital Anderson impurity model by means of continuous time quantum Monte Carlo, exact diagonalization, and Hartree-Fock calculations. The dependence of the electronic excitation spectra and thermodynamic ground-state properties on the hybridization strength and the form of the Coulomb interaction is systematically investigated for impurity occupation number N ≈ 6. With increasing hybridization strength, a Kondo resonance emerges, broadens and merges with some of the upper and lower Hubbard peaks. Concomitantly, there is an increase of charge fluctuations at the impurity site. In contrast to the single-orbital model, some atomic multiplet peaks and exchange split satellites persist despite strong charge fluctuations. We find that Hund's coupling leads to a state that may be characterized as an itinerant single atom magnet. As the filling is increased, the magnetic moment decreases, but the spin freezing phenomenon persists up to N ≈ 8. When the hybridization is weak, the positions of atomic ionization peaks are rather sensitive to shifts of the impurity on-site energies. This allows to distinguish atomic ionization peaks from quasiparticle peaks or satellites in the electronic excitation spectra. On the methodological side we show that a comparison between the spectra obtained from Monte Carlo and exact diagonalization calculations is possible if the charge fluctuations are properly matched.

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Graphene as a Reversible Spin Manipulator of Molecular Magnets

Cited by 73 publications

References 23 publications

Manipulation of spin state of iron porphyrin by chemisorption on magnetic substrates

Manipulation of spin state of iron porphyrin by chemisorption on magnetic substrates

Mixed configuration ground state in iron(II) phthalocyanine

Electronic excitation spectra of the five-orbital Anderson impurity model: From the atomic limit to itinerant atomic magnetism

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