Ising-Type Magnetic Anisotropy in a Cobalt(II) Nitronyl Nitroxide Compound: A Key to Understanding the Formation of Molecular Magnetic Nanowires

Caneschi, Andréa; Gatteschi, Dante; Lalioti, Nikolia; Sessoli, Roberta; Sorace, Lorenzo; Tangoulis, Vassilis; Vindigni, Alessandro

doi:10.1002/1521-3765(20020104)8:1<286::aid-chem286>3.0.co;2-d

Cited by 108 publications

(67 citation statements)

References 24 publications

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“…The S Ն 1 spin model can be applied to the following magnetic systems: arrays of weakly interacting magnetic nanoparticles, 4,5 nanoscale single-molecule magnets such as Mn 12 and Fe 8 , 6-8 a Mn͑III͒ 2 Ni͑II͒ single-chain magnet, 10,11 and a Co ferrimagnetic compound. 9 To understand spin relaxation in the S Ն 1 spin model, we assume that the spin system is weakly linearly coupled to a surrounding phonon bath in d dimensions. Since the phonon bath has much shorter relaxation time than the spin system, it is assumed that each spin is independently coupled to the bath.…”

Section: Formalism For Phonon-assisted Transition Ratessupporting

confidence: 68%

Transition rates for aS≥1spin model coupled to ad-dimensional phonon bath

Park

2008

Phys. Rev. B

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We consider a S Ն 1 spin model ͑or a generalized Blume-Capel model͒ weakly coupled to a d-dimensional phonon bath and investigate transition rates between different spin configurations. This study is motivated by understanding magnetization relaxation as a function of temperature in diverse magnetic systems such as arrays of magnetic nanoparticles and magnetic molecules. We assume that the magnetization of the spin system relaxes through consecutive emission or absorption of a single phonon. From a weak, linear spin-phonon coupling Hamiltonian, we derive transition rates that would be used to examine dynamic properties of the system in kinetic Monte Carlo simulations. Although the derived phonon-assisted transition rates satisfy detailed balance, in the case of two-and three-dimensional phonon baths, transitions between degenerate states are not allowed. ͑This is a major difference of the phonon-assisted transition rates from the Metropolis and Glauber transition rates.͒ Thus, if there are no alternative paths along which the spin system can relax, the relaxation time diverges. Otherwise, the system finds other paths, which leads to an increase in the relaxation time and energy barrier. However, when higher-order phonon processes are included in the transition rates, it is found that the system can reach the states which were inaccessible due to the forbidden transitions. As a result, the system recovers some of the dynamic properties obtained using the Glauber transition rate.

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Section: Formalism For Phonon-assisted Transition Ratessupporting

confidence: 68%

Transition rates for aS≥1spin model coupled to ad-dimensional phonon bath

Park

2008

Phys. Rev. B

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“…10,23,31 The primitive magnetic cell is made up of three cobalt ions and three radicals. The spins are arranged in a helical structure, with the helix axis coincident with the crystallographic c axis of the chain.…”

Section: The Modelmentioning

confidence: 99%

Finite-size effects on the dynamic susceptibility of CoPhOMe single-chain molecular magnets in presence of a static magnetic field

et al. 2011

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The static and dynamic properties of the single-chain molecular magnet [Co(hfac)2NITPhOMe] are investigated in the framework of the Ising model with Glauber dynamics, in order to take into account both the effect of an applied magnetic field and a finite size of the chains. For static fields of moderate intensity and short chain lengths, the approximation of a mono-exponential decay of the magnetization fluctuations is found to be valid at low temperatures; for strong fields and long chains, a multi-exponential decay should rather be assumed. The effect of an oscillating magnetic field, with intensity much smaller than that of the static one, is included in the theory in order to obtain the dynamic susceptibility χ(ω). We find that, for an open chain with N spins, χ(ω) can be written as a weighted sum of N frequency contributions, with a sum rule relating the frequency weights to the static susceptibility of the chain. Very good agreement is found between the theoretical dynamic susceptibility and the ac susceptibility measured in moderate static fields (H dc ≤ 2 kOe), where the approximation of a single dominating frequency turns out to be valid. For static fields in this range, new data for the relaxation time, τ versus H dc , of the magnetization of CoPhOMe at low temperature are also well reproduced by theory, provided that finite-size effects are included.

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“…Only part of the magnetization curve is known because the exchange energy scale is very high in terms of accessible magnetic fields. Experiments show a metamagnetic jump at low fields, much less than the value expected for full saturation [5,6].…”

Section: Introductionmentioning

confidence: 99%

Field-induced disorder point in noncollinear Ising spin chains

2004

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We perform a theoretical study of a non-collinear Ising ferrimagnetic spin chain inspired by the compound Co(hfac)2NITPhOMe. The basic building block of its structure contains one Cobalt ion and one organic radical each with a spin 1/2. The exchange interaction is strongly anisotropic and the corresponding axes of anisotropy have a period three helical structure. We introduce and solve a model Hamiltonian for this spin chain. We show that the present compound is very close to a so-called disorder point at which there is a massive ground state degeneracy. We predict the equilibrium magnetization process and discuss the impact of the degeneracy on the dynamical properties by using arguments based on the Glauber dynamics.

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Ising-Type Magnetic Anisotropy in a Cobalt(II) Nitronyl Nitroxide Compound: A Key to Understanding the Formation of Molecular Magnetic Nanowires

Cited by 108 publications

References 24 publications

Transition rates for aS≥1spin model coupled to ad-dimensional phonon bath

Transition rates for aS≥1spin model coupled to ad-dimensional phonon bath

Finite-size effects on the dynamic susceptibility of CoPhOMe single-chain molecular magnets in presence of a static magnetic field

Field-induced disorder point in noncollinear Ising spin chains

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