Realizing All-Spin–Based Logic Operations Atom by Atom

Khajetoorians, Alexander A.; Wiebe, Jens; Chilian, Bruno; Wiesendanger, R.

doi:10.1126/science.1201725

Cited by 392 publications

(367 citation statements)

References 24 publications

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“…Spin-bearing ad-atoms can be arranged in a specific manner on a surface by atom-positioning techniques, and moreover, those atoms can be individually probed by STM/STS. 29,30 However, this piece-by-piece assembly of the atoms is a very timeconsuming process and is inherently difficult to scale up toward larger functional structures. Also, the current lithographic technology does not allow for atomic precision.…”

Section: The Journal Of Physical Chemistry Lettersmentioning

confidence: 99%

Emergence of On-Surface Magnetochemistry

Ballav

Wäckerlin

Siewert

et al. 2013

J. Phys. Chem. Lett.

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The control of exchange coupling across the molecule−substrate interface is a key feature in molecular spintronics. This Perspective reviews the emerging field of on-surface magnetochemistry, where coordination chemistry is applied to surface-supported metal porphyrins and metal phthalocyanines to control their magnetic properties. The particularities of the surface as a multiatomic ligand or "surface ligand" are introduced. The asymmetry involved in the action of a chemical ligand and a surface ligand on the same planar complexes modifies the well-established "trans effect" to the notion of the "surface-trans effect". As ad-complexes on ferromagnetic substrates are usually exchange-coupled, the magnetochemical implications of the surface-trans effect are of particular interest. The combined action of the different ligands allows for the reproducible control of spin states in on-surface supramolecular architectures and opens up new ways toward building and operating spin systems at interfaces. Notably, spin-switching has been demonstrated to be controlled collectively via the interaction with a ligand (chemical selectivity) and individually via local addressing at the interface.A century ago, Alfred Werner laid the foundation of modern coordination chemistry, an achievement for which he was awarded the Nobel Prize in Chemistry in 1913. The innovative concept of primary and secondary valences in coordination complexes that he introduced has since then developed into oxidation states and coordination numbers and become textbook knowledge for introductory chemistry. 1 Briefly, the transition-metal ion in a given coordination complex with a fixed oxidation state can be either diamagnetic or paramagnetic, depending on the number of the ligands as well as their nature. It is the ligands that are responsible for the splitting of the d orbitals of the metal ion into t 2g and e g levels, which are at the heart of ligand field theory (LFT). 1 Thereby, ligand coordination directly alters the magnetic properties. Among the existing coordination complexes, particularly spin-bearing four-coordinated square-planar porphyrins and phthalocyanines have received much attention during the last six decades. Here, the coordination number of the metal ion and hence its magnetic properties can be easily modified by coordination with external axial ligands leading to five/six-fold coordination complexes. 2 Recently, on-surface coordination chemistry of metal porphyrins and metal phthalocyanines has raised increasing attention. 3−5 In this field of research, coordination chemistry of the planar molecules is studied in the presence of a surface ligand and an optional axial ligand binding to the free on-top site. A central issue is whether the known gas-phase coordination chemistry concepts remain valid for ligand coordination of spin-bearing planar metal−organic molecules assembled on (magnetic) surfaces. Emerging evidence shows that due to the surface−molecule interaction, novel magnetochemical effects arise beyond those known...

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Section: The Journal Of Physical Chemistry Lettersmentioning

confidence: 99%

Emergence of On-Surface Magnetochemistry

Ballav

Wäckerlin

Siewert

et al. 2013

J. Phys. Chem. Lett.

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“…Arrays of magnetic molecules inserted between conducting leads, moreover, provide an important forum to investigate fundamental magnetic properties of finite one-dimensional Ising or Heisenberg chains [14][15][16] as well as potential for electrical and thermal control of the magnetic state. Certain classes of molecules, e.g., metal-phthalocyanines (MPc) and metal-porhyrins (MP) present chemical stability with specific optical and electrical properties make them highly appreciated for technological applications including organic field effect transistors [17,18], light emitting devices [19,20] and photovoltaic cells [21], and for fundamental studies [7,[22][23][24][25][26][27].While incorporation of magnetic elements in molecular compounds can have a significant effect on the overall molecular transport properties [7], the main established route to spintronics manipulations entails external magnetic fields [2] or ferromagnetic electrodes [28,29], often exploiting spin transfer torques from spin-polarized scattering [30] or Coulomb interaction [31]. Here, we propose a different route to molecular spintronics based on voltage induced control of magnetic interactions that allows for all electrical control of the transport properties.…”

mentioning

confidence: 99%

Voltage-Induced Switching Dynamics of a Coupled Spin Pair in a Molecular Junction

et al. 2016

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Molecular spintronics is made possible by the coupling between electronic configuration and magnetic polarization of the molecules. For control and application of the individual molecular states it is necessary to both read and write their spin states. Conventionally, this is achieved by means of external magnetic fields or ferromagnetic contacts, which may change the intentional spin state and may present additional challenges when downsizing devices. Here, we predict that coupling magnetic molecules together opens up possibilities for all electrical control of both the molecular spin states as well as the current flow through the system. Tuning between the regimes of ferromagnetic and anti-ferromagnetic exchange interaction, the current can be, at least, an order of magnitude enhanced or reduced. The effect is susceptible to the tunnel coupling and molecular level alignment which can be used to achieve current rectification. Molecular spintronics is a field which aims to merge the flexibility of synthetic design of molecular compounds with novel functionalities offered by magnetic properties in conjunction with electronics circuits [1]. Magnetically active molecules have been used to demonstrate spin valve effect using external magnetic fields [2], stochastic switching between high and low conductive states by transitions between spin singlet and triplet ground states [3][4][5][6], controlled transport properties via paramagnetic atoms [7], as well as their potential for quantum based computation [8][9][10][11][12][13]. Arrays of magnetic molecules inserted between conducting leads, moreover, provide an important forum to investigate fundamental magnetic properties of finite one-dimensional Ising or Heisenberg chains [14][15][16] as well as potential for electrical and thermal control of the magnetic state. Certain classes of molecules, e.g., metal-phthalocyanines (MPc) and metal-porhyrins (MP) present chemical stability with specific optical and electrical properties make them highly appreciated for technological applications including organic field effect transistors [17,18], light emitting devices [19,20] and photovoltaic cells [21], and for fundamental studies [7,[22][23][24][25][26][27].While incorporation of magnetic elements in molecular compounds can have a significant effect on the overall molecular transport properties [7], the main established route to spintronics manipulations entails external magnetic fields [2] or ferromagnetic electrodes [28,29], often exploiting spin transfer torques from spin-polarized scattering [30] or Coulomb interaction [31]. Here, we propose a different route to molecular spintronics based on voltage induced control of magnetic interactions that allows for all electrical control of the transport properties. Deriving from local exchange interactions between the localized spin moments and the electrons in paramagnetic molecules, an indirect effective spinspin interaction is generated between the molecular spin moments through the electron tunneling between the molecules [32...

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“…The use of spin as the information conveying entity has stirred much excitement due to its extraordinary properties of information storage, speed, and low-energy consumption [1][2][3]. Miniaturization is quickly proceeding, reaching very small domain-wall devices [4], atomic-size devices [5], and the realm of molecular devices [2,[6][7][8][9]. Among all these possibilities, antiferromagnetically (AFM) coupled devices have recently received a lot of attention.…”

mentioning

confidence: 99%

Correlation-Mediated Processes for Electron-Induced Switching between Néel States of Fe Antiferromagnetic Chains

et al. 2013

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The controlled switching between two quasistable Néel states in adsorbed antiferromagnetic Fe chains has recently been achieved by Loth et al. [Science 335, 196 (2012)] using tunneling electrons from an STM tip. In order to rationalize their data, we evaluate the rate of tunneling electron-induced switching between the Néel states. Good agreement is found with the experiment, permitting us to identify three switching mechanisms: (i) The search for nanoscale electronic devices has prompted intense research in the field of nanomagnetism. The use of spin as the information conveying entity has stirred much excitement due to its extraordinary properties of information storage, speed, and low-energy consumption [1][2][3]. Miniaturization is quickly proceeding, reaching very small domain-wall devices [4], atomic-size devices [5], and the realm of molecular devices [2,[6][7][8][9]. Among all these possibilities, antiferromagnetically (AFM) coupled devices have recently received a lot of attention. The AFM characteristics make these devices very well fitted for quantum computation since they naturally involved entangled states [10,11]. Moreover, the storage in AFM devices is particularly robust due to the lack of a total magnetic moment. However, this robustness has deterred their use because changing their magnetic state becomes difficult [12].Recently, Loth and co-workers succeeded in controllably switching the spin states of AFM atomic chains [12]. Two quasistable Néel states, exhibiting alternating spin directions on the atoms along the chain, were evidenced in Fe chains adsorbed on a CuN=Cuð100Þ surface. Loth and co-workers showed that the Néel states can be switched by tunneling electrons injected from a polarized scanning tunneling microscope (STM) tip into one of the atoms of the chain. This demonstrated the possibility of storing information on the atomic-scale antiferromagnet. Theoretical predictions show that writing and reading spin states entail fundamental problems associated with the quantum nature of the process [13]. Spin manipulation by tunneling electrons has been pictured as due to a spintorque mechanism where spin angular momentum from the electron is transferred into the atomic spin system [14][15][16]. However, due to the lack of magnetic moment in AFM systems, spin manipulation must follow a different mechanism. Unavoidably, spin manipulations and excitations are closely related [17]. Indeed, switching between Néel states has been experimentally associated with overcoming an activation energy [12]. However, in the case of degenerate Néel states, resonant transitions should be expected. Hence, the experimental data raise many questions regarding the possibility of resonant switching, the efficiency of activated switching, the nature of the involved excitations, and the physics at play in AFM spin torque. In summary, a complete view of the switching process is missing.In this Letter, we reveal the switching mechanisms at play in the experiment of Ref. [12]. The mechanisms turn out to be rich and ...

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Realizing All-Spin–Based Logic Operations Atom by Atom

Cited by 392 publications

References 24 publications

Emergence of On-Surface Magnetochemistry

Emergence of On-Surface Magnetochemistry

Voltage-Induced Switching Dynamics of a Coupled Spin Pair in a Molecular Junction

Correlation-Mediated Processes for Electron-Induced Switching between Néel States of Fe Antiferromagnetic Chains

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