Spin Quantum Tunneling via Entangled States in a Dimer of Exchange-Coupled Single-Molecule Magnets

Tiron, Raluca; Wernsdorfer, Wolfgang; Foguet-Albiol, Dolos; Aliaga‐Alcalde, Núria; Christou, George

doi:10.1103/physrevlett.91.227203

Cited by 87 publications

(67 citation statements)

References 24 publications

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“…Until recently, such intermolecular exchange interactions have been assumed to be negligibly small. However, our recent studies on several SMMs suggest that in most SMMs exchange interactions lead to a significant influence on the tunnel process 19,20,21,22,23 . The main difference between dipolar and exchange interactions are: (i) dipolar interactions are long range whereas exchange interactions are usually short range;…”

Section: Intermolecular Dipolar and Exchange Interactionsmentioning

confidence: 99%

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Landau-Zener tunneling in the presence of weak intermolecular interactions in a crystal ofMn4single-molecule magnets

et al. 2005

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A Mn4 single-molecule magnet (SMM), with a well isolated spin ground state of S = 9/2, is used as a model system to study Landau-Zener (LZ) tunneling in the presence of weak intermolecular dipolar and exchange interactions. The anisotropy constants D and B are measured with minor hysteresis loops. A transverse field is used to tune the tunnel splitting over a large range. Using the LZ and inverse LZ method, it is shown that these interactions play an important role in the tunnel rates. Three regions are identified: (i) at small transverse fields, tunneling is dominated by single tunnel transitions; (ii) at intermediate transverse fields, the measured tunnel rates are governed by reshuffling of internal fields, (iii) at larger transverse fields, the magnetization reversal starts to be influenced by the direct relaxation process, and many-body tunnel events may occur. The hole digging method is used to study the next-nearest neighbor interactions. At small external fields, it is shown that magnetic ordering occurs which does not quench tunneling. An applied transverse field can increase the ordering rate. Spin-spin cross-relaxations, mediated by dipolar and weak exchange interactions, are proposed to explain additional quantum steps.

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Section: Intermolecular Dipolar and Exchange Interactionsmentioning

confidence: 99%

“…However, our recent studies on several SMMs suggest that in most SMMs exchange interactions lead to a significant influence on the tunnel process 18 . Recently, this intermolecular exchange interaction was used to couple antiferromagnetically two SMMs, each acting as a bias on its neighbor 19,20,21,22,23 .…”

Section: Introductionmentioning

confidence: 99%

Landau-Zener tunneling in the presence of weak intermolecular interactions in a crystal ofMn4single-molecule magnets

et al. 2005

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“…As far as we know, all other reported experiments for SMM systems start from strongly polarized initial states. 20 Consequently, we decided to do simulations of SMM's in FCC lattices, because Eq. (5) gives then a value, 0.73, for p, which differs significantly from 1/2.…”

Section: B Comparison With Experiments and Simulationsmentioning

confidence: 99%

Time relaxation of interacting single-molecule magnets

Fernández

Alonso

2005

Phys. Rev. B

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We study the relaxation of interacting single-molecule magnets (SMMs) in both spatially ordered and disordered systems. The tunneling window is assumed to be, as in Fe 8 , much narrower than the dipolar field spread. We show that relaxation in disordered systems differs qualitatively from relaxation in fully occupied cubic and Fe 8 lattices. We also study how line shapes that develop in "hole-digging" experiments evolve with time t in these fully occupied lattices. We show (1) that the dipolar field h scales as t p in these hole line shapes and show (2) how p varies with lattice structure. Line shapes are not, in general, Lorentzian. More specifically, in the lower portion of the hole, they behave as (| h | /t p ) (1/p)−1 if h is outside the tunnel window. This is in agreement with experiment and with our own Monte Carlo results.

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“…That is because the system can be better schematized by three interacting SMMs. In the past pairs of weakly coupled Mn 4 clusters have been widely investigated [14,15] and demonstrated to show quantum coherence [16]. However a fascinating new situation is observed in Dy 3 because the two states of the ground doublet are distinguished by a different spin chirality and they cannot be related one to each other by a simple exchange of the magnetic sites.…”

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Spin Chirality in a Molecular Dysprosium Triangle: The Archetype of the Noncollinear Ising Model

et al. 2008

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Single crystal magnetic studies combined with a theoretical analysis show that cancellation of the magnetic moments in the trinuclear Dy 3+ cluster [Dy3(µ3-OH)2L3Cl(H2O)5]Cl3, resulting in a non-magnetic ground doublet, originates from the non-collinearity of the single ion easy axes of magnetization of the Dy 3+ ions that lie in the plane of the triangle at 120 • one from each other. This gives rise to a peculiar chiral nature of the ground non-magnetic doublet and to slow relaxation of the magnetization with abrupt accelerations at the crossings of the discrete energy levels.PACS numbers: 71.79. Ej, 75.10.Jm,75.50.Xx, 75.30.Cr Molecular nanomagnetism has provided benchmark systems to investigate new and fascinating phenomena in magnetism [1,2] like magnetic memory at the molecular level [3], quantum tunneling of the magnetization [4,5], or destructive interferences in the tunneling pathways [6]. In this field rare earth ions like dysprosium(III) are currently investigated because of their large magnetic anisotropy and high magnetic moment [7]. In the course of our synthetic efforts to obtain new molecular nanomagnets based on rare-earth ions we recently obtained the trinuclear(where L is the anion of ortho-vanillin) [8], hence abbreviated as Dy 3 , which possesses an almost trigonal (C 3h ) symmetry (see Figure 1 and EPAPS for more information) [9].Preliminary powder magnetic measurements measure- Figure 1. To the best of our knowledge an experimental realization of this simple but fascinating spin structure is unprecedented.To verify our hypothesis larger crystals (of size ca. 1 mm 3 ) of one of the two compounds were grown according to [8] through very slow evaporation of the solvent. This allowed an accurate face indexing of the crystal on the X-ray diffractometer and the investigation of the magnetic anisotropy by using an horizontal sample rotator in the SQUID magnetometer (see EPAPS for experimental details) [9]. Scans in different crystallographic planes allowed us to determine the three magnetic anisotropy axes, denoted as X, Y and Z. The two structurally equivalent Dy 3 molecules in the unit cell have the Dy 3 planes almost perpendicular to Z and one side of the triangle parallel to Y (see Fig. 1). Magnetization vs. field curves along these axes are given in Figure 2a. Along X and Y a sudden jump around 8 kOe is observed while an almost linear but weaker magnetization is observed along Z. In Figure 2b the temperature dependence of the magnetization along the three axes measured at 1 kOe, and thus before the jump to saturation, are shown. The inplane X and Y directions are very similar and M tends to zero at low temperatures, confirming a non-magnetic ground state, while a weaker signal is observed along Z.The observed behaviour has been modelled using the canonical formalism of the statistical thermodynamics

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Spin Quantum Tunneling via Entangled States in a Dimer of Exchange-Coupled Single-Molecule Magnets

Cited by 87 publications

References 24 publications

Landau-Zener tunneling in the presence of weak intermolecular interactions in a crystal ofMn4single-molecule magnets

Landau-Zener tunneling in the presence of weak intermolecular interactions in a crystal ofMn4single-molecule magnets

Time relaxation of interacting single-molecule magnets

Spin Chirality in a Molecular Dysprosium Triangle: The Archetype of the Noncollinear Ising Model

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