Magnetic reversal of a quantum nanoferromagnet

Gauyacq, J.P.; Lorente, Nicolás

doi:10.1103/physrevb.87.195402

Cited by 13 publications

(14 citation statements)

References 60 publications

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“…The skyrmion state is then stable when it is the ground stable but also when it is an excited state. However, the system described by equation (1) is not alone in space; the spin structure in Fig.1 is adsorbed on a metal surface and the inelastic collision of an electron from the substrate on one of the structure sites can induce a transition from the upper state to the lower state (electron-hole pair creation) and is responsible for the finite lifetime of the excited state (see a discussion of the decay rate induced by electron-hole pair creation in 49,51 and the application to spin decay in 52,53,54,55 ). This process can involve thermally excited electrons but the decay is already present at vanishing temperature.…”

Section: Stability Of the Skyrmion And Ferromagnetic Structuresmentioning

confidence: 99%

“…However, as discussed below, highly excited states Transition between FM and Sk states is only possible via correlation. The various spins in the system are entangled, so that by touching one site in the structure, all the spins in the system can be modified (see similar situations in 54,58,59,60 ). In the present system, correlation between FM-type and Sk-type states exists but is weak and so is the probability for an electron to induce FM-Sk transitions by collision on one of the sites in the crown.…”

Section: Stability Of the Skyrmion And Ferromagnetic Structuresmentioning

confidence: 99%

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A model for individual quantal nano-skyrmions

Gauyacq

Lorente

2019

J. Phys.: Condens. Matter

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A quantal model description of a discrete localized skyrmion singularity embedded in a ferromagnetic environment is proposed. It allows discussing the importance of various parameters in the appearance of a quantal skyrmion singularity. Analysis of the skyrmion reveals a few specific quantal properties: presence of a whole series of skyrmion states, nonclassical nature of the local spins, presence of superposition states and presence of extraskyrmion states due to the quantization of the central spin of the singularity. The interaction of an electron, tunneling or substrate, with the skyrmion is also described allowing a new view at the origin of the skyrmion stability as well as the possibility to discriminate between ferromagnetic and skyrmion phase in an Inelastic Electron Tunneling Spectroscopy (IETS) experiment, based on the skyrmion quantal properties.

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Section: Stability Of the Skyrmion And Ferromagnetic Structuresmentioning

confidence: 99%

Section: Stability Of the Skyrmion And Ferromagnetic Structuresmentioning

confidence: 99%

A model for individual quantal nano-skyrmions

Gauyacq

Lorente

2019

J. Phys.: Condens. Matter

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“…The Hamilton operator in (1) includes the standard spin operatorsŜ i , uniaxial onsite anisotropy K and a magnetic field =  ( ) B B 0, 0, z . This Hamiltonian models an effective quantum spin representing a nanoparticle, a molecule or an atomic cluster [20,24,31] = --…”

Section: Time Evolution Of Expectation Valuesmentioning

confidence: 99%

“…i with n-number of harmonics. Hence, the spin value s is not at all present in the analytical expression (20). As i is an integer and s is an integer or half-integer in (19) the fundamental frequency corresponds to the very specific choices of…”

Section: Non-harmonic Revival Of Expectation Valuesmentioning

confidence: 99%

“…Meanwhile, the quantum dynamical phenomena become increasingly important also in solid state physics. Particularly, quantum mechanical tunneling or the non-classical field dependence of magnetization has been reported for nano-magnets [20], molecules [21,22] and single atoms [23]. Therefore, instead of studies of timeaveraged properties like, e.g., magnetization curves [23,24], nowadays the emphasis is put on the time dependent behavior of magnetization [25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

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Quantum revivals and magnetization tunneling in effective spin systems

et al. 2016

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Quantum mechanical objects or nano-objects have been proposed as bits for information storage. While time-averaged properties of magnetic, quantum-mechanical particles have been extensively studied experimentally and theoretically, experimental investigations of the real time evolution of magnetization in the quantum regime were not possible until recent developments in pump-probe techniques. Here we investigate the quantum dynamics of effective spin systems by means of analytical and numerical treatments. Particular attention is paid to the quantum revival time and its relation to the magnetization tunneling. The quantum revival time has been initially defined as the recurrence time of a total wave-function. Here we show that the quantum revivals of wave-functions and expectation values in spin systems may be quite different which gives rise to a more sophisticated definition of the quantum revival within the realm of experimental research. Particularly, the revival times for integer spins coincide which is not the case for half-integer spins. Furthermore, the quantum revival is found to be shortest for integer ratios between the on-site anisotropy and an external magnetic field paving the way to novel methods of anisotropy measurements. We show that the quantum tunneling of magnetization at avoided level crossing is coherent to the quantum revival time of expectation values, leading to a connection between these two fundamental properties of quantum mechanical spins.

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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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Magnetic reversal of a quantum nanoferromagnet

Cited by 13 publications

References 60 publications

A model for individual quantal nano-skyrmions

A model for individual quantal nano-skyrmions

Quantum revivals and magnetization tunneling in effective spin systems

Encoding Information on the Excited State of a Molecular Spin Chain

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