Real-space observation of spin-split molecular orbitals of adsorbed single-molecule magnets

Schwöbel, Jörg; Fu, Ying-Shuang; Brede, Jens; DiLullo, Andrew; Hoffmann, Germar; Klyatskaya, Svetlana; Rüben, Mario; Wiesendanger, R.

doi:10.1038/ncomms1953

Cited by 140 publications

(121 citation statements)

References 26 publications

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“…Also, we have demonstrated an unprecedented level of spectroscopic information combining spin, orbital, and energy resolution. High spatial resolution of spin-split molecular orbitals has been obtained in some small metal-organic compounds exhibiting spin-dependent contrast [31,32] with magnetic tips. However, this study presents results of spin-resolved orbital imaging of single-atom wave functions.…”

Section: (D) and 2(e) Provided That P T = 0 And Aφ/w < 90mentioning

confidence: 99%

Spin-sensitive shape asymmetry of adatoms on noncollinear magnetic substrates

et al. 2016

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The spin-resolved density of states of Co atoms on a noncollinear magnetic support displays a distinct shape contrast, which is superimposed on the regular height contrast in spin-polarized scanning tunneling microscopy. The apparent atom height follows the well-known cosine dependence on the angle formed by the tip and adatom local magnetization directions, whereas the shape contrast exhibits a sine dependence. We explain this effect in terms of a noncollinear spin density induced by the substrate, which in our case is the spin spiral of the Mn monolayer on W(110). The two independent contrast channels, apparent height and shape, are identified with the Co magnetization projections onto two orthogonal axes. As a result, all components of the overall atom magnetic moment vector can be determined with a single spin-sensitive tip in the absence of an external magnetic field. This result should be general for any atom deposited on noncollinear magnetic layers. DOI: 10.1103/PhysRevB.93.125424The control of the spin degree of freedom down to the single-atom limit is nowadays a central research issue [1][2][3][4][5][6][7], fostered by the increasing need for miniaturization and lowering power consumption in communication technologies. The most suitable technique to address the problem is spinpolarized scanning tunneling microscopy (SP-STM) [8], which has proven to be an excellent tool to perform single-atom magnetometry [1,6]. The design of magnetic structures with a given functionality calls for atomic-scale engineering by means of atomic manipulation or self-assembly of lowdimensional structures. Both of them can be combined with SP-STM [6,7,9,10]. For that reason, getting insight into the underlying physics of SP-STM and extending its range of applications is of crucial relevance. The SP-STM principle is the magneto-conductance effect in magnetic tunnel junctions [8,[11][12][13][14], and relies on probing the imbalance between majority and minority spins in the local density of states (LDOS) with respect to a particular magnetic quantization axis. Following the same notation as in Ref. [15], the spinpolarized tunneling current at sample bias V readswhere ρ T and P T are the tip's density of states and spin polarization,ρ s andm s the integrated sample total density of states and magnetization at r (tip position), and θ the angle formed between the tip and local sample magnetization. As a consequence, a SP-STM tip is only sensitive to the projection onto its magnetization direction, m s cos θ , and not to all other components ofm s . Here we show that the situation is radically different if the substrate's magnetic ground state is noncollinear within the spatial extent of an atomic wave function. Owing to the breaking of translational symmetry in spin space associated with the noncollinearity, the atoms' apparent shapes become distorted in spin-resolved STM images. We find that the strength of such distortion provides a quantitative measurement of the total spin component orthogonal to the default sensitivity direct...

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Section: (D) and 2(e) Provided That P T = 0 And Aφ/w < 90mentioning

confidence: 99%

Spin-sensitive shape asymmetry of adatoms on noncollinear magnetic substrates

et al. 2016

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“…For this reason it is vital to choose molecules with maximum structural robustness upon adsorption [1][2][3]. To this end, the phthalocyanine and porphyrin families are popular choices due to their planar geometry [4][5][6][7][8][9]. However, in some cases, the strong interaction between the metal ion of such flat molecules and the substrate can modify its electronic states and even quench its magnetic moment [10].…”

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confidence: 99%

Graphene-mediated exchange coupling between a molecular spin and magnetic substrates

et al. 2013

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Using first-principles calculations we demonstrate sizable exchange coupling between a magnetic molecule and a magnetic substrate via a graphene layer. As a model system we consider cobaltocene (CoCp2) adsorbed on graphene deposited on Ni(111). We find that the magnetic coupling between the molecule and the substrate is antiferromagnetic and varies considerably depending on the molecule structure, the adsorption geometry, and the stacking of graphene on Ni(111). We show how this coupling can be tuned by intercalating a magnetic monolayer, e.g. Fe or Co, between graphene and Ni(111). We identify the leading mechanism responsible for the coupling to be the spatial and energy matching of the frontier orbitals of CoCp2 and graphene close to the Fermi level, and we demonstrate the role of graphene as an electronic decoupling layer, yet allowing spin communication between molecule and substrate.PACS numbers: 71.15. Mb, 75.50.Xx, 81.05.ue The emerging field of organic spintronics capitalizes on the novel functionalities achieved when organic molecules are adsorbed on magnetic substrates. The ability to manipulate and tune these functionalities is an important goal. Several problems remain however, before such systems can be incorporated into new technological devices. One in particular is the capability to adsorb molecules on surfaces without any detrimental effects being caused to either the structural or magnetic properties of the molecule. For this reason it is vital to choose molecules with maximum structural robustness upon adsorption [1][2][3]. To this end, the phthalocyanine and porphyrin families are popular choices due to their planar geometry [4][5][6][7][8][9]. However, in some cases, the strong interaction between the metal ion of such flat molecules and the substrate can modify its electronic states and even quench its magnetic moment [10].The use of non-planer molecules, such as metallocenes, can minimize this effect. Metallocenes are composed of a 3d transition-metal ion sandwiched between two cyclopentadienyls (Cp). Depending on the metal ion species, both non-magnetic and paramagnetic behavior can be found [11]. The spin of the metal ion is shielded from the surface by the cage formed by the two Cp rings, reducing the possibility that it will be modified substantially after adsorption. Unfortunately, the deposition of metallocenes on metallic surfaces is a difficult process [12] and, in some cases, complete dissociation of the molecule occurs [13,14].The intercalation of a graphene spacer layer between the reactive surface and the metallocene can reduce the possibility of molecular dissociation during deposition. Additionally, evidence of charge transfer at moleculegraphene-Ni(111) interfaces [15,16] and the theoretical prediction of large charge transfer from cobaltocene (CoCp 2 ) to graphene [17] would suggest that a magnetic coupling between cobaltocene and the Ni(111) surface through the graphene layer is still achievable.In this Letter, we predict, by first principles electronic structure metho...

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“…In contrast to the Tb 3+ ion in the previously studied late-Lanthanide analogue TbPc 2 [15,18], the Nd 3+ ion has a larger ionic radius with more delocalized 4f -electrons. As a consequence, the 4f -electrons undergo a stronger hybridization with the Pc ligands.…”

Section: Electronic Structure Inmentioning

confidence: 77%

“…The late-lanthanide phthalocyanines, for example, TbPc 2 have been investigated quite extensively in the past and have been found to be stable on many surfaces [14][15][16][17][18]. This is not necessarily true for the early-lanthanide phthalocyanines.…”

Section: Stability Of Chemisorbed Moleculesmentioning

confidence: 99%

Spin-Hybrids: A Single-Molecule Approach to Spintronics

Bürgler

Heß

Esat

et al. 2016

e-J. Surf. Sci. Nanotech.

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Molecular spintronics aims at exploiting and controlling spin-dependent transport processes at the molecular level. Achieving this aim requires not only appropriate molecules, molecular structures and preparation procedures. Equally important is the understanding and engineering of the electronic and spin-dependent interactions between different molecular species, molecule and substrate, as well as molecule and electrodes. These interactions may not only determine the spin-dependent functionality of the molecular structures, but also their integrity on the substrate. Likewise, there may be also a modification of the surface properties below and in the vicinity of a molecule. We have investigated several molecules on different metallic surfaces, among them magnetic Nd doubledecker phthalocyanines, a cubane-type {Ni4} complex with single-molecule magnet properties, and a nonmagnetic triazine-based molecule. For NdPc2 molecules adsorbed on a Cu(100) surface, our scanning tunneling microscopy and spectroscopy studies show specific electronic states of the molecule-substrate complex. We find that the electric field between STM tip and sample must be taken into account to properly describe the electronic states associated with the upper Pc ligand.

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Real-space observation of spin-split molecular orbitals of adsorbed single-molecule magnets

Cited by 140 publications

References 26 publications

Spin-sensitive shape asymmetry of adatoms on noncollinear magnetic substrates

Spin-sensitive shape asymmetry of adatoms on noncollinear magnetic substrates

Graphene-mediated exchange coupling between a molecular spin and magnetic substrates

Spin-Hybrids: A Single-Molecule Approach to Spintronics

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