Electronic structure of a<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi mathvariant="normal">Mn</mml:mi><mml:mn>12</mml:mn></mml:msub></mml:math>molecular magnet: Theory and experiment

Boukhvalov, Danil W.; Al-Saqer, M.; Kurmaev, E.Z.; Moewes, A.; Galakhov, V. R.; Finkelstein, L. D.; Chiuzbăian, S. G.; Neumann, M.; Dobrovitski, V. V.; Katsnelson, M. I.; Lichtenstein, A. I.; Harmon, B. N.; Endo, Kazunaka; North, J. M.; Dalal, Naresh S.

doi:10.1103/physrevb.75.014419

Cited by 46 publications

(51 citation statements)

References 47 publications

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“…This feature of the HOMO and LUMO does not change with inclusion of a proper value of the U term although the HOMO-LUMO energy gap increases with the U term. This was shown in previous DFT+ U calculations, 44,49 in contrast to the result discussed in Ref. 16.…”

Section: B Effect Of Geometry Relaxationcontrasting

confidence: 56%

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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Section: B Effect Of Geometry Relaxationcontrasting

confidence: 56%

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

et al. 2010

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“…Moreover, recent experiments on the electron transport through SMMs [4], and predicted connection between the transport and spin tunneling [5], make SMMs good candidates for interesting spintronics studies. Progress in this area -synthesis of novel SMMs with optimized properties, design and analysis of the transport experiments, possible uses in information processing -demands detailed theoretical investigations of the magnetic and electronic structure of SMMs [6,7,8,9,10]. Among other factors, the many-body correlations caused by the Coulomb repulsion between electrons, may be important.…”

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confidence: 99%

Correlation effects in the electronic structure of theMn4molecular magnet

et al. 2008

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We present joint theoretical-experimental study of the correlation effects in the electronic structure of (pyH)3[Mn4O3Cl7(OAc)3]·2MeCN molecular magnet (Mn4). Describing the many-body effects by cluster dynamical mean-field theory, we find that Mn4 is predominantly Hubbard insulator with strong electron correlations. The calculated electron gap (1.8 eV) agrees well with the results of optical conductivity measurements, while other methods, which neglect many-body effects or treat them in a simplified manner, do not provide such an agreement. Strong electron correlations in Mn4 may have important implications for possible future applications.PACS numbers: 75.50. Xx,71.15.Mb, Single molecule magnets (SMMs), made of exchangecoupled magnetic ions surrounded by large organic ligands, represent a novel interesting class of magnetic materials. They are of fundamental interest as test systems for studying magnetism at nanoscale, and interplay between the structural, electronic, and magnetic properties. SMMs demonstrate fascinating mixture of clasiscal and quantum properties: as classical superparamagnets, they possess large anisotropy and magnetic moment, but also exhibit interesting mesoscopic quantum spin effects [1,2,3]. Moreover, recent experiments on the electron transport through SMMs [4], and predicted connection between the transport and spin tunneling [5], make SMMs good candidates for interesting spintronics studies. Progress in this area -synthesis of novel SMMs with optimized properties, design and analysis of the transport experiments, possible uses in information processing -demands detailed theoretical investigations of the magnetic and electronic structure of SMMs [6,7,8,9,10]. Among other factors, the many-body correlations caused by the Coulomb repulsion between electrons, may be important. E.g., in transition metal-oxide systems [11], which share many similarities with SMMs, strong correlations may form the Mott-Hubbard insulating state [12], where the nature of the charge and spin excitations is drastically different from the predictions of standard band-insulator theory. This affects the basic properties of the system (e.g., exchange interactions), and drastically changes charge and spin transport.In this joint experimental-theoretical work, we present a detailed study of the many-body effects in electronic structure of SMMs (pyH) 3 [Mn 4 O 3 Cl 7 (OAc) 3 ]·2MeCN (denoted below as Mn 4 for brevity) [19]. We use the cluster LDA+DMFT method [13] which combines the realistic ab initio calculations based on the local density approximation (LDA), and the accurate description of the correlation effects within the cluster dynamical mean field theory (CDMFT). Using the electron gap as a most convenient benchmark, we show that the gap value (1.8 eV) calculated within LDA+CDMFT is in good agreement with the optical conductivity measurements (showing the peak corresponding to vertical transitions at ∼1.8 eV). The approaches which neglect the electron correlations (LDA), or treat these correlation in a simplifi...

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“…6(b)], which agrees with previous studies. 40,41 We also find that the HOMO-LUMO gap increases monotonically and then saturates around U = 5-6 eV, and the HOMO-LUMO gap for ligand -CHCl 2 is consistently smaller than that for ligand -CH 3 . The ∼1 eV HOMO-LUMO gap at U = 4 eV for ligand -CH 3 in low-spin state matches the experimental value.…”

Section: Magnetic Anisotropy Barriermentioning

confidence: 60%

“…The ∼1 eV HOMO-LUMO gap at U = 4 eV for ligand -CH 3 in low-spin state matches the experimental value. 40,42 As for the low spin states, GGA+U calculations do not show much difference in the electronic properties discussed in previous sections, since both GGA and GGA+U calculations give a large gap for the spin-down channels. The same conclusion, that DFT+U calculations show results similar to GGA calculations for Mn 12 low spin states, has also been made for Mn 12 adsorption on a Ni(111) surface.…”

Section: Magnetic Anisotropy Barriermentioning

confidence: 96%

Single-molecule magnetMn12on graphene

Fry

Cheng

2014

Phys. Rev. B

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We study energetics, electronic and magnetic structures, and magnetic anisotropy barriers of a monolayer of single-molecule magnets (SMM), [Mn 12 O 12 (COOR) 16 ](H 2 O) 4 (abbreviated as Mn 12 , with R=H, CH 3 , C 6 H 5 and CHCl 2 ), on a graphene surface using spin-polarized density-functional theory with generalized gradient corrections and the inclusion of van der Waals interactions. We find that Mn 12 molecules with ligands -H, -CH 3 , and -C 6 H 5 are physically adsorbed on graphene through weak van der Waals interactions, and a much stronger ionic interaction occurs using a -CHCl 2 ligand. The strength of bonding is closely related to the charge transfer between the molecule and the graphene sheet and can be manipulated by strain in the graphene; specifically, tension enhances n-doping of graphene and compression encourages p-doping. The magnetic anisotropy barrier is computed by including the spin-orbit interaction within density-functional theory. The barriers for the Mn 12 molecules with ligands -H, -CH 3 and -C 6 H 5 on graphene surfaces remain unchanged (within 1 K) from those of isolated molecules because of their weak interaction, and a much larger reduction (10 K) is observed when using the -CHCl 2 ligand on graphene due to a substantial structural deformation as a consequence of the much stronger interaction. Neither strain in graphene nor charge transfer affects the magnetic anisotropy barrier significantly. Finally, we discuss the effect of strong correlation in the high spin state of a Mn 12 SMM and the consequence in SMM-surface adsorption.

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Electronic structure of aMn12molecular magnet: Theory and experiment

Cited by 46 publications

References 47 publications

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

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

Correlation effects in the electronic structure of theMn4molecular magnet

Single-molecule magnetMn12on graphene

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