Current-Driven Spin Dynamics of Artificially Constructed Quantum Magnets

Khajetoorians, Alexander A.; Baxevanis, B.; Hübner, Christoph; Schlenk, T.; Krause, Stefan; Wehling, T. O.; Lounis, Samir; Lichtenstein, A. I.; Pfannkuche, Daniela; Wiebe, Jens; Wiesendanger, R.

doi:10.1126/science.1228519

Cited by 202 publications

(227 citation statements)

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“…Dimers of transition metals, as the small-size end point of SMMs, have been theoretically proposed to be promising candidates for novel information storage devices 6 . An alternative approach for the design of magnetic materials based on a few or even single atoms as magnetic units is ad-atoms on metallic surfaces 7,8 . The key property among these actually very different examples, and of any nanoscale magnetic system, is a large magnetic anisotropy energy.…”

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confidence: 99%

Giant magnetic anisotropy and tunnelling of the magnetization in Li2(Li1−xFex)N

et al. 2014

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Large magnetic anisotropy and coercivity are key properties of functional magnetic materials and are generally associated with rare earth elements. Here we show an extreme, uniaxial magnetic anisotropy and the emergence of magnetic hysteresis in Li 2 (Li 1 À x Fe x )N. An extrapolated, magnetic anisotropy field of 220 T and a coercivity field of over 11 T at 2 K outperform all known hard ferromagnets and single-molecular magnets. Steps in the hysteresis loops and relaxation phenomena in striking similarity to single-molecular magnets are particularly pronounced for xo o1 and indicate the presence of nanoscale magnetic centres. Quantum tunnelling, in the form of temperature-independent relaxation and coercivity, deviation from Arrhenius behaviour and blocking of the relaxation, dominates the magnetic properties up to 10 K. The simple crystal structure, the availability of large single crystals and the ability to vary the Fe concentration make Li 2 (Li 1 À x Fe x )N an ideal model system to study macroscopic quantum effects at elevated temperatures and also a basis for novel functional magnetic materials.

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confidence: 99%

Giant magnetic anisotropy and tunnelling of the magnetization in Li2(Li1−xFex)N

et al. 2014

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“…Long wave-length excitations of complex magnets such as yttrium iron garnet (YIG) can be treated by such a model by coarse graining, i.e., letting each spin represents the magnetization of a unit cell. Artificially fabricated exchangecoupled atomic spins on a substrate [17] is another physical realization of this model. The magnetization dynamics can be described by the so-called Landau-Lifshitz-Miyazaki-Seki (LLMS) equations [11]:…”

Section: Modelmentioning

confidence: 99%

“…The memory kernel with relaxation time τ c does not affect the repartition. Although we consider an exponential memory kernel here, we envision that the obtained energy repartition principle (17) should be robust to the specific form of the kernels. The generalization to two spins in the unit cell leads to acoustic and optical magnon branches and can be used to study ferrimagnets and antiferromagnets [27].…”

Section: A Linear Spin-wave Theorymentioning

confidence: 99%

Energy repartition in the nonequilibrium steady state

2017

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The concept of temperature in nonequilibrium thermodynamics is an outstanding theoretical issue. We propose an energy repartition principle that leads to a spectral (mode-dependent) temperature in steady-state nonequilibrium systems. The general concepts are illustrated by analytic solutions of the classical Heisenberg spin chain connected to Langevin heat reservoirs with arbitrary temperature profiles. Gradients of external magnetic fields are shown to localize spin waves in a Wannier-Zeemann fashion, while magnon interactions renormalize the spectral temperature. Our generic results are applicable to other thermodynamic systems such as Newtonian liquids, elastic solids, and Josephson junctions.

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“…Particularly recent advances in scanning tunneling microscopy lead to enormous progress in the probing and manipulation of these systems including writing, reading, and processing of information from atomic scale bits via e.g. spintransfer torques [14,15] and spin-polarized spectroscopy techniques [16,17].In all of these cases, the coupling between adatom and substrate is central to determine the magnetic properties of the system. Thus, changes in the quantum state of the substrate can directly affect the adatom magnetism, as studies of superconducting substrates demonstrated [18,19].…”

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confidence: 99%

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Optically and Electrically Controllable Adatom Spin–orbital Dynamics in Transition Metal Dichalcogenides

et al. 2017

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We analyze the interplay of spin-valley coupling, orbital physics and magnetic anisotropy taking place at single magnetic atoms adsorbed on semiconducting transition metal dichalcogenides, MX2 (M = Mo, W; X = S, Se). Orbital selection rules turn out to govern the kinetic exchange coupling between the adatom and charge carriers in the MX2 and lead to highly orbitally dependent spin-flip scattering rates, as we illustrate for the example of transition metal adatoms with d 9 configuration. Our ab initio calculations suggest that d 9 configurations are realizable by single Co, Rh, or Ir adatoms on MoS2, which additionally exhibit a sizable magnetic anisotropy. We find that the interaction of the adatom with carriers in the MX2 allows to tune its behavior from a quantum regime with full Kondo screening to a regime of "Ising spintronics" where its spin-orbital moment acts as classical bit, which can be erased and written electronically and optically.Transition metal adatoms on surfaces provide ideal model systems for fundamental studies of quantum many-body phenomena ranging from magnetism [1][2][3] and Kondo physics [4][5][6][7] to topological states of matter [8][9][10] and Majorana modes [11][12][13]. Moreover, these systems are promising as ultimately miniaturized building blocks of spintronic devices and logic gates. Particularly recent advances in scanning tunneling microscopy lead to enormous progress in the probing and manipulation of these systems including writing, reading, and processing of information from atomic scale bits via e.g. spintransfer torques [14,15] and spin-polarized spectroscopy techniques [16,17].In all of these cases, the coupling between adatom and substrate is central to determine the magnetic properties of the system. Thus, changes in the quantum state of the substrate can directly affect the adatom magnetism, as studies of superconducting substrates demonstrated [18,19]. In the light of time-dependent phenomena, substrates which allow for ultrafast manipulation of their electronic states by electronic or optical means are particularly interesting but actual realizations have been lacking so far.In this letter, we show that strong spin-valley coupling and peculiar orbital physics make monolayers of transition metal dichalcogenides (TMDCs), MX 2 (M = Mo, W; X = S, Se) ideal substrates in this context. MX 2 materials allow for ultrafast optical control of their electronic states and for charge doping by external gates, which turn out to provide control over spin-flip scattering of transition metal (TM) adatoms on a monolayer MX 2 . We illustrate this result based on ab initio simulations of single Co, Rh, or Ir adatoms on MoS 2 and a generic model Hamiltonian description. Our calculations show, that these magnetic adatoms exhibit a dou- * bin.shao@uni-bremen.de blet ground state which is separated from excited states by a sizable magnetic anisotropy > 10 meV and realizes an "Ising" spin-orbital moment. We analyze the kinetic exchange scattering of adatom and substrate electrons, and demons...

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Current-Driven Spin Dynamics of Artificially Constructed Quantum Magnets

Cited by 202 publications

References 48 publications

Giant magnetic anisotropy and tunnelling of the magnetization in Li2(Li1−xFex)N

Giant magnetic anisotropy and tunnelling of the magnetization in Li2(Li1−xFex)N

Energy repartition in the nonequilibrium steady state

Optically and Electrically Controllable Adatom Spin–orbital Dynamics in Transition Metal Dichalcogenides

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