Controlling the Magnetization Direction in Molecules via Their Oxidation State

Atodiresei, Nicolae; Dederichs, P. H.; Mokrousov, Yuriy; Bergqvist, Lars; Bihlmayer, Gustav; Blügel, Stefan

doi:10.1103/physrevlett.100.117207

Cited by 46 publications

(75 citation statements)

References 24 publications

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“…With respect to bulk molecular crystals, the planar and open coordination structure of the self-assembled Fe array makes such a system extremely sensitive to chemisorption, providing straightforward control of the preferred Fe spin orientation. Through the analysis of the XAS and XMCD spectra, we can further identify the cause for the easy-axis switch in the metal-organic complexes, revealing a different mechanism from the one proposed by Atodiresei and co-workers 18 based on the control of the metal oxidation state. Our calculations show that only the ligand field is affected by O 2 adsorption, whereas the formal Fe oxidation does not change.…”

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confidence: 79%

“…Recent studies showed that the magnetization direction of surface-supported paramagnetic molecules can be controlled through exchange coupling with a magnetic film, which provides robust ferromagnetic properties but does not enable each molecule to be switched independently from the substrate or its neighbours 16,17 . Alternatively, theoretical work suggested that the sign of magnetic anisotropy could be reversed in metal-organic complexes by exploiting oxidation processes that affect the hybridization of molecular orbitals with metal states carrying non-zero orbital magnetization 18 . Here, we investigate supramolecular self-assembly on a non-magnetic Cu surface as a means to produce two-dimensional (2D) arrays of regularly spaced Fe spins, the magnitude and magnetic anisotropy of which are manipulated by lateral and axial molecular ligands.…”

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confidence: 99%

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Supramolecular control of the magnetic anisotropy in two-dimensional high-spin Fe arrays at a metal interface

et al. 2009

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. The control of magnetic anisotropy is a key issue in the development of molecule-metal interfaces for magnetic applications, both at the single-molecule 12 and extended-film level 13 . In metallic multilayers used as storage media or spin-valve devices at present, tuning of the magnetic anisotropy is achieved either by a careful choice of the overlayer/substrate composition and thickness or by oxidation of the magnetic elements 11,14,15 . Recent studies showed that the magnetization direction of surface-supported paramagnetic molecules can be controlled through exchange coupling with a magnetic film, which provides robust ferromagnetic properties but does not enable each molecule to be switched independently from the substrate or its neighbours 16,17 . Alternatively, theoretical work suggested that the sign of magnetic anisotropy could be reversed in metal-organic complexes by exploiting oxidation processes that affect the hybridization of molecular orbitals with metal states carrying non-zero orbital magnetization 18 . Here, we investigate supramolecular self-assembly on a non-magnetic Cu surface as a means to produce two-dimensional

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Supramolecular control of the magnetic anisotropy in two-dimensional high-spin Fe arrays at a metal interface

et al. 2009

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“…The ultimate goal of this approach is to construct devices in which the adsorbed organic molecules on surfaces are the main functional units. 1 Among the advantages of using molecules in future electronic devices, it is worth mentioning the possibility of designing such devices at a molecular scale to construct organic field-effect transistors [2][3][4] or ultrahigh-density memory circuits. 5 A promising way to manufacture a molecular electronic device is to use self-assembled monolayers ͑SAM͒ 6 adsorbed on a specific substrate.…”

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confidence: 99%

Role of the van der Waals interactions on the bonding mechanism of pyridine on Cu(110) and Ag(110) surface: First-principles study

et al. 2008

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We performed density-functional calculations aimed to investigate the adsorption mechanism of a single pyridine ͑C 5 H 5 N͒ molecule on Cu͑110͒ and Ag͑110͒ surfaces. Our ab initio simulations show that, in the ground state, the pyridine molecule adsorbs with its molecular plane perpendicular to these substrates and is oriented along the ͓001͔ direction. In this case, the bonding mechanism involves a bond through the lone-pair electrons of the nitrogen atom. When the heterocyclic ring is parallel to the surface, the bonding takes place via -like molecular orbitals. However, depending on the position of the N atom on the surface, the planar adsorption configuration can relax to a perpendicular geometry. The role of the long-range van der Waals interactions on the adsorption geometries and energies was analyzed in the framework of the semiempirical method proposed by Grimme ͓J. Comput. Chem. 27, 1787 ͑2006͔͒. We demonstrate that these dispersion effects are very important for geometry and electronic structure of flat adsorption configurations.

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“…The choice of the calculated moleculeferromagnetic surface systems can be understood as following: (i) although having a low reactivity, Bz (C 6 H 6 ) is an aromatic 6π-electron system [13] that can form sandwich type compounds with d-metals [14] and chemisorbs on reactive surfaces [15,16]; (ii) a high-reactive 5π-electron system, Cp (C 5 H 5 ) strongly interacts with dmetals and forms an aromatic 6π-electron system in sandwich type molecules like ferrocene [13]. However, Cp can be brought on the surface by decomposition of the ferrocene molecule which occurs after its adsorption on metallic surfaces [17]; (iii) an 8π-electron system, Cot (C 8 H 8 ), binds strongly the metal atoms by forming an aromatic 10π-electron system [13] and is well known to react even with f -electrons of rare earth metals [18,19] forming sandwich type molecules and long nanowires [20].…”

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Design of the Local Spin Polarization at the Organic-Ferromagnetic Interface

Brede²,

et al. 2010

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By means of ab initio calculations and spin-polarized scanning tunneling microscopy experiments we show how to manipulate the local spin-polarization of a ferromagnetic surface by creating a complex energy dependent magnetic structure. We demonstrate this novel effect by adsorbing organic molecules containing π(pz)-electrons onto a ferromagnetic surface, in which the hybridization of the out-of-plane pz atomic type orbitals with the d-states of the metal leads to the inversion of the spin-polarization at the organic site due to a pz − d Zener exchange type mechanism. As a key result, we demonstrate that it is possible to selectively inject spin-up and spin-down electrons from the same ferromagnetic surface, an effect which can be exploited in future spintronic devices.PACS numbers: 68.43.Bc,71.15.Mb Combining molecular electronics with spintronics represents one of the most exciting avenues in building future nanoelectronic devices [1][2][3]. For example, widely used in spintronic applications, the spin valve [4] is a layered structure of two ferromagnetic electrodes separated by a nonmagnetic spacer to decouple the two electrodes and allows spin-polarized electrons to travel through it. The efficiency of a spin valve depends crucially on the spin injection into and spin transport throughout the nonmagnetic spacer. On one side, since organic molecules are made of light elements with weak spin-orbit coupling as C and H, their use as spacer materials is very promising for transport properties since the spin coherence over time and distance is much larger than in the conventional semiconductors present in today's devices [5][6][7]. On the other side, the spin injection is mostly controlled by the ferromagnetic-organic layer interface [8,9] which is responsible for the significant spin loss in devices [10]. Therefore, a large effort is made to control the electronic properties at the organic-magnetic interfaces and, in this context, the theoretical first-principles calculations represent an indispensable tool to understand and guide experiments toward more efficient devices.In this Letter we propose a simple way to manipulate the local spin-polarization of a ferromagnetic surface by flat adsorbing organic molecules containing π(p z )-electrons onto it. As a consequence, around the Fermi level an inversion of the local spin-polarization at the organic site occurs with respect to the ferromagnetic surface due to a complex energy-and spin-dependent electronic structure of the organic-metal interface. The interaction between the molecule and the ferromagnetic surface reveals a mechanism similar to the p z − d Zener exchange [11] and enables a selective control of electron injection with different spins [i.e. up(↑) or down(↓)] from the same ferromagnetic surface within a specific energy The pz atomic orbitals in the spin-up channel hybridize with the majority (spin-up) states of the Fe atoms forming bonding (at lower energies) and antibonding (at higher energies) states some of them being pushed above the Fermi level...

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Controlling the Magnetization Direction in Molecules via Their Oxidation State

Cited by 46 publications

References 24 publications

Supramolecular control of the magnetic anisotropy in two-dimensional high-spin Fe arrays at a metal interface

Supramolecular control of the magnetic anisotropy in two-dimensional high-spin Fe arrays at a metal interface

Role of the van der Waals interactions on the bonding mechanism of pyridine on Cu(110) and Ag(110) surface: First-principles study

Design of the Local Spin Polarization at the Organic-Ferromagnetic Interface

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