Magnetic properties of high-nuclearity spin clusters. Fourteen- and fifteen-oxovanadium(IV) clusters

Barra, Anne Laure; Gatteschi, Dante; Pardi, Luca; Mueller, A.; Doering, Joachim

doi:10.1021/ja00048a023

Cited by 148 publications

(84 citation statements)

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“…In the absence of anisotropy the ground state is four-fold degenerate, and it is made up of two doublets. The lowest lying excited states form a quartet which is separated from the ground state doublets by ≈ 3.7 K. The splitting between the lowest energy multiplets from the rest of the spectrum has been found from EPR spectra to be ∼ 500 K [35]. Magnetic anisotropy leads to tunnel splittings between the two doublets, which are ∼ 10 −2 K [36], in contrast with the very small values for the other two molecules (∼ 10 −7 − 10 −11 K).…”

Section: V15mentioning

confidence: 95%

Magnetic anisotropy in the molecular complexV15

Konstantinidis

Coffey

2002

Phys. Rev. B

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We apply degenerate perturbation theory to investigate the effects of magnetic anisotropy in the magnetic molecule V15. Magnetic anisotropy is introduced via Dzyaloshinskii-Moriya (DM) interaction in the full Hilbert space of the system. Our model provides an explanation for the rounding of transitions in the magnetization as a function of applied field at low temperature, from which an estimate for the DM interaction is found. We find that the calculated energy differences of the lowest energy states are consistent with the available data. Our model also offers a novel explanation for the hysteretic nature of the time-dependent magnetization data.

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Section: V15mentioning

confidence: 95%

Magnetic anisotropy in the molecular complexV15

Konstantinidis

Coffey

2002

Phys. Rev. B

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“…[1][2][3][4][5] It is the complex of formula K 6 V Different experiments on the magnetization process have shown that the magnetization changed adiabatically in a fast sweeping field, and a magnetic plateau appeared in a slow sweeping field due to thermal bath attached to the molecule. [6][7][8] The latter phenomenon, which is called the phonon bottleneck effect, is theoretically analyzed from a general point of view of the magnetic Foehn effect.…”

Section: Introductionmentioning

confidence: 99%

ESR intensity and the Dzyaloshinsky-Moriya interaction of the nanoscale molecular magnet V15

2012

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The intensity of electron spin resonance (ESR) of the nanoscale molecular magnet V 15 is studied. We calculate the temperature dependence of the intensity at temperatures from high to low. In particular, we find that the low-temperature ESR intensity is significantly affected by the Dzyaloshinsky-Moriya interaction. I. INTRODUCTIONThe V 15 molecule has been one of promising nanometer-scale molecular magnets since it was first synthesized. Different experiments on the magnetization process have shown that the magnetization changed adiabatically in a fast sweeping field, and a magnetic plateau appeared in a slow sweeping field due to thermal bath attached to the molecule. are not yet fully understood.In this paper, first we numerically calculate the temperature dependence of the ESR intensity of V 15 using a new numerical method (the double Chebyshev polynomial method) of calculating the Kubo formula. We find that the model Hamiltonian for V 15 including the DMI successfully reproduces the experimental temperature dependence of the ESR intensity.Second we investigate the ESR at very low temperatures. We find that the intensity ratio (the intensity of V 15 divided by that of a spin 1/2) is affected by the DMI at small fields.We propose that experimental observation of the intensity ratio enables us to estimate the DMI in V 15 . Finally, we analyze the ESR at low temperatures using a triangle model whose 2 energy levels model the low-lying levels of V 15 . Figure 1 shows the structure of vanadium ions in V 15 . We consider the following spin II. MODEL AND FORMULATIONHamiltonian for V 15 . 17-19The first term on the right-hand side of Eq. (1) describes the Heisenberg interaction. Coefficients J ij take three values J, J 1 , and J 2 (|J| > |J 2 | > |J 1 |) depending on the bonds on the upper and lower hexagons. Three spins between two hexagons interact with the hexagons by J 1 and J 2 . There is no interaction among these three spins 3 . We set J = −800K, J 2 = −350K, and J 1 = −225K. 20 The second term describes the DMI. We assume the existence of DM vectors {D ij } at the bonds of J. In the third term, H denotes the static magnetic field applied to the molecule. We will ignore other effects such as dipolar fields, hyperfine interactions, and the crystal field, which are considered to be negligibly small.Indeed, the dipolar and hyperfine fields are estimated as 1 mK and 50 mK, respectively 7 .

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“…Among the vanadium-oxygen clusters [NHEt3] [henceforth, V 12(6 : 6)] have attracted attention as mixed valent systems situated at the crossroads between well-coupled materials such as K6[V15As6O42(H2O)] 8H2O (V15 for short) and smaller clusters where the magnetic exchange interaction is rela tively weak. [1][2][3][4][5][6][7] Figure 1(a) shows the molecular structure of the [ v 8X A s 8O40(H2O)]4-cluster anion, the building block of V 12(8:4). It consists of a V4+ central square capped by slightly distorted, mixed-valent squares, with an effective formal 4.5+ oxidation state.1,5-7 The vanadium squares are bridged by diarsenite (As2O^-) groups, and there is a slight asymmetry to the structure due to the displacement of one of the octahedral vanadium centers toward the encapsulated wa ter molecule.7 The anionic building block of the V 12(6 : 6) material is slightly different [ Fig.1(b)].…”

Section: Introductionmentioning

confidence: 99%