| 1. |
- Baljozovic, Milos, et al.
(författare)
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Self-Assembly and Magnetic Order of Bi-Molecular 2D Spin Lattices of M(II,III) Phthalocyanines on Au(111)
- 2021
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Ingår i: MAGNETOCHEMISTRY. - : MDPI. - 2312-7481. ; 7:8
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Tidskriftsartikel (refereegranskat)abstract
- Single layer low-dimensional materials are presently of emerging interest, including in the context of magnetism. In the present report, on-surface supramolecular architecturing was further developed and employed to create surface supported two-dimensional binary spin arrays on atomically clean non-magnetic Au(111). By chemical programming of the modules, different checkerboards were produced combining phthalocyanines containing metals of different oxidation and spin states, diamagnetic zinc, and a metal-free 'spacer'. In an in-depth, spectro-microscopy and theoretical account, we correlate the structure and the magnetic properties of these tunable systems and discuss the emergence of 2D Kondo magnetism from the spin-bearing components and via the physico-chemical bonding to the underlying substrate. The contributions of the individual elements, as well as the role of the electronic surface state in the bottom substrate, are discussed, also looking towards further in-depth investigations.
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| 2. |
- Girovsky, Jan, et al.
(författare)
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Long-range ferrimagnetic order in a two-dimensional supramolecular Kondo lattice
- 2017
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Realization of long-range magnetic order in surface-supported two-dimensional systems has been challenging, mainly due to the competition between fundamental magnetic interactions as the short-range Kondo effect and spin-stabilizing magnetic exchange interactions. Spin-bearing molecules on conducting substrates represent a rich platform to investigate the interplay of these fundamental magnetic interactions. Here we demonstrate the direct observation of long-range ferrimagnetic order emerging in a two-dimensional supramolecular Kondo lattice. The lattice consists of paramagnetic hexadeca-fluorinated iron phthalocyanine (FeFPc) and manganese phthalocyanine (MnPc) molecules co-assembled into a checkerboard pattern on single-crystalline Au(111) substrates. Remarkably, the remanent magnetic moments are oriented in the out-of-plane direction with significant contribution from orbital moments. First-principles calculations reveal that the FeFPc-MnPc antiferromagnetic nearest-neighbour coupling is mediated by the Ruderman-Kittel-Kasuya-Yosida exchange interaction via the Au substrate electronic states. Our findings suggest the use of molecular frameworks to engineer novel low-dimensional magnetically ordered materials and their application in molecular quantum devices.
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| 3. |
- Girovsky, Jan, et al.
(författare)
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Antiferromagnetic coupling of Cr-porphyrin to a bare Co substrate
- 2014
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 90:22, s. 220404-
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of an antiferromagnetic coupling of the magnetic moment of chromium(II) tetraphenylporphyrin (CrTPP) molecules to the magnetization of the clean ferromagnetic Co(001) substrate. We assign this unusual molecule-substrate exchange coupling to the less than half-filled chromium 3d orbitals interacting with Co valence band electrons via porphyrin-ligand molecular orbitals. X-ray magnetic circular dichroism, x-ray photoelectron spectroscopy, and scanning tunneling microscopy are combined with DFT + U calculations and provide evidence for a surprising type of antiferromagnetic 90 degrees indirect magnetic exchange coupling.
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| 4. |
- Girovsky, Jan, et al.
(författare)
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Investigating magneto-chemical interactions at molecule-substrate interfaces by X-ray photo-emission electron microscopy
- 2014
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 50:40, s. 5190-5192
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Tidskriftsartikel (refereegranskat)abstract
- The magneto-chemical interaction of spin-bearing molecules with substrates is interesting from a coordination chemistry point of view and relevant for spintronics. Unprecedented insight is provided by X-ray photo-emission electron microscopy combined with X-ray magnetic circular dichroism spectroscopy. Here the coupling of a Mn-porphyrin ad-layer to the ferromagnetic Co substrate through suitably modified interfaces is analyzed with this technique.
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| 5. |
- Shchyrba, Aneliia, et al.
(författare)
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Controlling the dimensionality of on-surface coordination polymers via endo- or exoligation
- 2014
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 136:26, s. 9355-9363
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Tidskriftsartikel (refereegranskat)abstract
- The formation of on-surface coordination polymers is controlled by the interplay of chemical reactivity and structure of the building blocks, as well as by the orientating role of the substrate registry. Beyond the predetermined patterns of structural assembly, the chemical reactivity of the reactants involved may provide alternative pathways in their aggregation. Organic molecules, which are transformed in a surface reaction, may be subsequently trapped via coordination of homo- or heterometal adatoms, which may also play a role in the molecular transformation. The amino-functionalized perylene derivative, 4,9-diaminoperylene quinone-3,10-diimine (DPDI), undergoes specific levels of dehydrogenation (-1 H-2 or -3 H-2) depending on the nature of the present adatoms (Fe, Co, Ni or Cu). In this way, the molecule is converted to an endo- or an exoligand, possessing a concave or convex arrangement of ligating atoms, which is decisive for the formation of either ID or 2D coordination polymers.
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| 6. |
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| 7. |
- Waeckerlin, Christian, et al.
(författare)
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Magnetic exchange coupling of a synthetic Co(II)-complex to a ferromagnetic Ni substrate
- 2013
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 49:91, s. 10736-10738
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Tidskriftsartikel (refereegranskat)abstract
- On-surface assembly of a spin-bearing and non-aromatic porphyrin-related synthetic Co(II)-complex on a ferromagnetic Ni thin film substrate and subsequent magnetic exchange interaction across the interface were studied by scanning tunnelling microscopy (STM), X-ray absorption spectroscopy (XAS), X-ray magnetic circular dichroism (XMCD) and density functional theory +U (DFT + U) calculations.
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| 8. |
- Waeckerlin, Christian, et al.
(författare)
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Two-Dimensional Supramolecular Electron Spin Arrays
- 2013
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 25:17, s. 2404-2408
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Tidskriftsartikel (refereegranskat)abstract
- A bottom-up approach is introduced to fabricate two-dimensional self-assembled layers of molecular spin-systems containing Mn and Fe ions arranged in a chessboard lattice. We demonstrate that the Mn and Fe spin states can be reversibly operated by their selective response to coordination/decoordination of volatile ligands like ammonia (NH3).
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| 9. |
- Waeckerlin, Christian, et al.
(författare)
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On-surface coordination chemistry of planar molecular spin systems : novel magnetochemical effects induced by axial ligands
- 2012
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Ingår i: CHEMICAL SCIENCE. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 3:11, s. 3154-3160
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Tidskriftsartikel (refereegranskat)abstract
- Paramagnetic transition-metal complexes assembled on surfaces are of great interest for potential applications in organic spintronics. The magnetochemical interactions of the spin of the metal centers with both ferromagnetic surfaces and optional axial ligands are yet to be understood. We use a combination of X-ray magnetic circular dichroism (XMCD) and quantum-chemical simulations based on density functional theory (DFT + U) to investigate these metal-organic interfaces with chemically tunable magnetization. The interplay between an optional axial ligand (NO, spin S = 1/2 or NH3, S = 0) and Ni and Co ferromagnetic surfaces affecting the spin of Co(II) tetraphenylporphyrin (d(7), S = 1/2), Fe(II) tetraphenylporphyrin (d(6), S = 1), Mn(II) tetraphenylporphyrin (d(5), S = 5/2) and Mn(II) phthalocyanine (d(5), S = 3/2) is studied. We find that the structural trans effect on the surface rules the molecular spin state, as well as the sign and strength of the exchange interaction with the substrate. We refer to this observation as the surface spin-trans effect.
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