Excitation of spin waves by tunneling electrons in ferromagnetic and antiferromagnetic spin-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mfrac><mml:mrow><mml:mn>1</mml:mn></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:mfrac></mml:mrow></mml:math>Heisenberg chains

Gauyacq, J.P.; Lorente, Nicolás

doi:10.1103/physrevb.83.035418

Cited by 19 publications

(63 citation statements)

References 41 publications

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“…The odd Fe chains on Cu 2 N/Cu(100) are described using the same model as for our earlier studies on spin chains 25,35,36 . It assumes that each Fe atom bears a local S=2 spin, with anisotropy terms, coupled by Heisenberg exchange.…”

Section: A Model Description Of the Fe Chainsmentioning

confidence: 99%

Extremely long-lived magnetic excitations in supported Fe chains

Gauyacq

Lorente

2016

Phys. Rev. B

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We report on a theoretical study of the lifetime of the first excited state of spin chains made of an odd number of Fe atoms on Cu 2 N/Cu(100). Yan et al (Nat. Nanotech. 10, 40 (2015)) recently observed very long lifetimes in the case of Fe 3 chains. We consider the decay of the first excited state induced by electron-hole pair creation in the substrate. For a finite magnetic field, the two lowest-lying states in the chain have a quasi-Néel state structure.Decay from one state to the other strongly depends on the degree of entanglement of the local spins in the chain. The entanglement in the chain accounts for the long lifetimes that increase exponentially with chain length. Despite their apparently very different properties, the behaviour of odd and even chains is governed by the same kind of phenomena, in particular entanglement effects. The present results account quite well for the lifetimes recently measured by Yan et al on Fe 3

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Section: A Model Description Of the Fe Chainsmentioning

confidence: 99%

Extremely long-lived magnetic excitations in supported Fe chains

Gauyacq

Lorente

2016

Phys. Rev. B

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“…iÞN i ð2Þ (green diamonds). Many states i are excited by a tunneling electron, although many of them with a small probability that roughly exponentially decreases with the excitation energy [27]. The largest excitation probability corresponds to states i where the spin of the atom under the STM tip changes by ÁM % AE1.…”

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“…The first region, between 6 and 12 meV, corresponds to transitions where M changes in one of the end atoms of the chain; these are very efficient in shorter chains such as Fe 6 . This type of excitation is a quantized spin wave of the finite chain [27]. The second region, beyond 12 meV, corresponds to transitions that mix several configurations with two opposite antiferromagnetic domains (domain-wall formation).…”

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confidence: 99%

“…As a consequence, in a zero-order view of the Néel states, described as chains of atoms with alternating spins, electron-induced switching between pure Néel states does not exist. However, AFM chains described with Heisenberg couplings are strongly correlated [26,27]; i.e., the two Néel-like states, eigenstates of Hamiltonian (2), contain small components over a very large number of different configurations of atomic spins. Direct, quasiresonant electroninduced transitions between Néel-like states are then possible.…”

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confidence: 99%

“…The largest excitation probability corresponds to states i where the spin of the atom under the STM tip changes by ÁM % AE1. All the other states are excited via correlation, i.e., the fact that states 1 and i are not associated to a single configuration of local spins [27] but to a mixing of a large number of them from a configuration interaction point of view. As for the decay of the excited states, i, the lower-energy states decay preferentially toward Néel state 1 or 2, depending on which state they are configurationally closer.…”

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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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Encoding Information on the Excited State of a Molecular Spin Chain

Katcko

Urbain

Ngassam

et al. 2021

Adv Funct Materials

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The quantum states of nano‐objects can drive electrical transport properties across lateral and local‐probe junctions. This raises the prospect, in a solid‐state device, of electrically encoding information at the quantum level using spin‐flip excitations between electron spins. However, this electronic state has no defined magnetic orientation and is short‐lived. Using a novel vertical nanojunction process, these limitations are overcome and this steady‐state capability is experimentally demonstrated in solid‐state spintronic devices. The excited quantum state of a spin chain formed by Co phthalocyanine molecules coupled to a ferromagnetic electrode constitutes a distinct magnetic unit endowed with a coercive field. This generates a specific steady‐state magnetoresistance trace that is tied to the spin‐flip conductance channel, and is opposite in sign to the ground state magnetoresistance term, as expected from spin excitation transition rules. The experimental 5.9 meV thermal energy barrier between the ground and excited spin states is confirmed by density functional theory, in line with macrospin phenomenological modeling of magnetotransport results. This low‐voltage control over a spin chain's quantum state and spintronic contribution lay a path for transmitting spin wave‐encoded information across molecular layers in devices. It should also stimulate quantum prospects for the antiferromagnetic spintronics and oxides electronics communities.

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Excitation of spin waves by tunneling electrons in ferromagnetic and antiferromagnetic spin-12Heisenberg chains

Cited by 19 publications

References 41 publications

Extremely long-lived magnetic excitations in supported Fe chains

Extremely long-lived magnetic excitations in supported Fe chains

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

Encoding Information on the Excited State of a Molecular Spin Chain

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