Theory of Tunneling Spectroscopy in a<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>Mn</mml:mi><mml:mn>12</mml:mn></mml:msub></mml:math>Single-Electron Transistor by Density-Functional Theory Methods

Michalak, Lukasz; Canali, Carlo M.; Pederson, Mark R.; Paulsson, Magnus; Benza, V.

doi:10.1103/physrevlett.104.017202

Cited by 27 publications

(35 citation statements)

References 30 publications

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“…[3] Challenged by the promising molecular spintronics and quantum computing applications sophisticated SMMs based not only on 3d transition metals but also on the 4d and even on the lanthanide and actinide elements were developed. [4][5][6][7] The theoretical studies have mostly concentrated on the description of the resonant tunneling experiments, [8,9] ab initio simulations, [10][11][12] and investigation of the role of the correlation effects. [13] The single-molecule magnets consist of a core and bridging polynuclear complexes.…”

Section: Introductionmentioning

confidence: 99%

Nature of the ferromagnetic ground state in the Mn4molecular magnet

et al. 2014

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Using ab initio band structure and model calculations we studied magnetic properties of one of the Mn4 molecular magnets (Mn4(hmp)6), where two types of the Mn ions exist: Mn 3+ and Mn 2+ . The direct calculation of the exchange constants in the GGA+U approximation shows that in contrast to a common belief the strongest exchange coupling is not between two Mn 3+ ions (J bb ), but along two out of four exchange paths connecting Mn 3+ and Mn 2+ ions (J wb ). Within the perturbation theory we performed the microscopic analysis of different contributions to the exchange constants, which allows us to establish the mechanism for the largest ferromagnetic exchange. In the presence of the charge order the lowest in energy virtual excitations, contributing to the superexchange, will be not those across the Hubbard gap ∼ U , but will be those between the Mn 3+ and Mn 4+ ions, which cost much smaller energy V (≪ U ). Together with strong Hund's rule coupling and specific orbital order this leads to large ferromagnetic exchange interaction for two out of four Mn 2+ -Mn 3+pairs.

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Section: Introductionmentioning

confidence: 99%

Nature of the ferromagnetic ground state in the Mn4molecular magnet

et al. 2014

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“…Even though the Mn 12 is chemically bonded to the Au electrodes, the broadening of the relevant molecular orbitals is so small compared to its charging energy that the Kondo temperature is expected to be extremely low. In addition, these 14,15 and other calculations 16,17 demonstrate the importance of the internal magnetic degrees of freedom of the Mn 12 in electron transport, in contrast to typical quantum dots, regardless of the specific details of the coupling of the molecule to the electrodes.…”

Section: Introductionmentioning

confidence: 99%

Effects of bonding type and interface geometry on coherent transport through the single-molecule magnetMn12

et al. 2010

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We examine theoretically coherent electron transport through the single-molecule magnet Mn 12 , bridged between Au͑111͒ electrodes, using the nonequilibrium Green's function method and the density-functional theory. We analyze the effects of bonding type, molecular orientation, and geometry relaxation on the electronic properties and charge and spin transport across the single-molecule junction. We consider nine interface geometries leading to five bonding mechanisms and two molecular orientations: ͑i͒ Au-C bonding, ͑ii͒ Au-Au bonding, ͑iii͒ Au-S bonding, ͑iv͒ Au-H bonding, and ͑v͒ physisorption via van der Waals forces. The two molecular orientations of Mn 12 correspond to the magnetic easy axis of the molecule aligned perpendicular ͓hereafter denoted as orientation ͑1͔͒ or parallel ͓orientation ͑2͔͒ to the direction of electron transport. We find that the electron transport is carried by the lowest unoccupied molecular orbital ͑LUMO͒ level in all the cases that we have simulated. Relaxation of the junction geometries mainly shifts the relevant occupied molecular levels toward the Fermi energy as well as slightly reduces the broadening of the LUMO level. As a result, the current slightly decreases at low bias voltage. Our calculations also show that placing the molecule in the orientation ͑1͒ broadens the LUMO level much more than in the orientation ͑2͒ due to the internal structure of the Mn 12 . Consequently, junctions with the former orientation yield a higher current than those with the latter. Among all of the bonding types considered, the Au-C bonding gives rise to the highest current ͑about one order of magnitude higher than the Au-S bonding͒, for a given distance between the electrodes. The current through the junction with other bonding types decreases in the order of Au-Au, Au-S, and Au-H. Importantly, the spin-filtering effect in all the nine geometries stays robust and their ratios of the majority-spin to the minorityspin transmission coefficients are in the range of 10 3 -10 8 . The general trend in transport among the different bonding types and molecular orientations obtained from this study may be applicable to other single-molecule magnets.

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“…(46) was later extended and generalized by Michalak et al (2010) to describe collective magnetic excitations of Mn 12 -acetate SMMs, which can be detected in the tunneling conductance of spin SET experiments (Heersche et al, 2006;Jo et al, 2006). As mentioned above, the neutral Mn 12 -acetate molecule is a SMM characterized by a ground-state spin S ¼ 10 and a uniaxial anisotropy barrier of order of 5 meV.…”

Section: Many-body Description Of Ground-state and Low-lying Excitationsmentioning

confidence: 95%

“…In the following sections, we will review some recent work in this direction (Michalak et al, 2010;Nossa et al, 2013) based on DFT, emphasizing the theoretical and computational problems encountered along the way.…”

Section: Mn 12mentioning

confidence: 99%

“…Here, Q is the excess charge of molecule being Q ¼ 0 for the neutral molecule, and Q ¼ AE1 is the excess charge for the cation and anion respectively. Within the formalism developed by Pederson and Khanna (1999), it is possible to use DFT to compute the total spin and anisotropy barrier of the three contiguous charge states Q ¼ 0,AE1 (Michalak et al, 2010). Then the effective spin Hamiltonian of Eq.…”

Section: Many-body Description Of Ground-state and Low-lying Excitationsmentioning

confidence: 99%

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