Resonant magnetization tunnelling in the half-integer-spin single-molecule magnet [PPh4][Mn12O12(O2CEt)16(H2O)4]

Hendrickson, David N.; Aubin, Sheila M. J.; Spagna, S.; Sager, R. E.; Eppley, Hilary J.; Christou, George

doi:10.1039/a800586i

Cited by 72 publications

(35 citation statements)

References 15 publications

(19 reference statements)

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“…However, external perturbations, such as nuclear hyperfine fields and/or dipolar fields, can remove the degeneracy of the sublevels, [17] and QTM becomes possible even at zero field. This effect has been observed in the half-integer spin systems such as [PPh 4 [18] (S = 19/2) and…”

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confidence: 87%

A Wheel‐Shaped Single‐Molecule Magnet of [Mn^II₃Mn^III₄]: Quantum Tunneling of Magnetization under Static and Pulse Magnetic Fields

Koizumi

Nihei

Shiga

et al. 2007

Chemistry A European J

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The reaction of N-(2-hydroxy-5-nitrobenzyl)iminodiethanol (=H3(5-NO2-hbide)) with Mn(OAc)2* 4 H2O in methanol, followed by recrystallization from 1,2-dichloroethane, yielded a wheel-shaped single-molecule magnet (SMM) of [MnII 3MnIII 4(5-NO2-hbide)6].5 C2H4Cl2 (1). In 1, seven manganese ions are linked by six tri-anionic ligands and form the wheel in which the two manganese ions on the rim and the one in the center are MnII and the other four manganese ions are MnIII ions. Powder magnetic susceptibility measurements showed a gradual increase with chimT values as the temperature was lowered, reaching a maximum value of 53.9 emu mol(-1) K. Analyses of magnetic susceptibility data suggested a spin ground state of S=19/2. The zero-field splitting parameters of D and B 0 4 were estimated to be -0.283(1) K and -1.64(1)x10(-5) K, respectively, by high-field EPR measurements (HF-EPR). The anisotropic parameters agreed with those estimated from magnetization and inelastic neutron scattering experiments. AC magnetic susceptibility measurements showed frequency-dependent in- and out-of-phase signals, characteristic data for an SMM, and an Arrhenius plot of the relaxation time gave a re-orientation energy barrier (DeltaE) of 18.1 K and a pre-exponential factor of 1.63x10(-7) s. Magnetization experiments on aligned single crystals below 0.7 K showed a stepped hysteresis loop, confirming the occurrence of quantum tunneling of the on magnetization (QTM). QTM was, on the other hand, suppressed by rapid sweeps of the magnetic field even at 0.5 K. The sweep-rate dependence of the spin flips can be understood by considering the Landau-Zener-Stückelberg (LZS) model.

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confidence: 87%

A Wheel‐Shaped Single‐Molecule Magnet of [Mn^II₃Mn^III₄]: Quantum Tunneling of Magnetization under Static and Pulse Magnetic Fields

Koizumi

Nihei

Shiga

et al. 2007

Chemistry A European J

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“…These results have now been confirmed, 3,4 and recent experiments have found similar effects in other systems of magnetic molecules. 5,6 The mesoscopic spin-10 magnetic subunits in Mn 12 are each made of 12 strongly superexchange-coupled Mn ions. It would be interesting to observe similar effects in macroscopic systems where the magnetic entities are composed of a larger number ͑thousands͒ of spins.…”

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confidence: 99%

Anomalous magnetic relaxation in ferritin

1997

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We report measurements in natural horse-spleen ferritin that provide a detailed mapping of the blocking temperature, T B , as a function of magnetic field over a broad range up to 20 kOe. Unlike most superparamagnetic materials where it decreases with applied field, T B increases with increasing field at small fields, reaching a maximum at Ϸ3 kOe before exhibiting the expected decrease. The hysteresis loops are anomalously ''pinched'' near zero field. Both observations are consistent with an effective energy barrier that is smaller at zero field than in small finite fields. This may arise from tunneling between pairs of states on opposite sides of the anisotropy barrier that are in resonance in zero magnetic field, regardless of particle size. However, direct measurements of the magnetic viscosity yield ambiguous results, leaving open other possible explanations. ͓S0163-1829͑97͒06441-2͔Quantum tunneling of magnetization has been the focus of renewed interest with the recent discovery 1,2 of resonant tunneling between spin states in the molecular-magnet Mn 12 acetate. The magnetic relaxation rate in Mn 12 was found to increase markedly whenever the applied magnetic field brings spin states on opposite sides of a potential barrier into resonance. These results have now been confirmed, 3,4 and recent experiments have found similar effects in other systems of magnetic molecules. 5,6 The mesoscopic spin-10 magnetic subunits in Mn 12 are each made of 12 strongly superexchange-coupled Mn ions. It would be interesting to observe similar effects in macroscopic systems where the magnetic entities are composed of a larger number ͑thousands͒ of spins. Molecular magnets such as Mn 12 consist of magnetic entities that are nominally identical and, therefore, have resonances at well-defined values of field. This is not the case for most other ensembles of small magnetic particles, which generally have a distribution of moments, anisotropies, and potential barriers. In such systems one expects there to be resonances for some particles at any given field, smearing out the effect and thereby making it unobservable. The only resonance that all particles have in common is the one at zero field, where spin-up and spindown levels are degenerate, and all pairs of states on opposite sides of the anisotropy barrier are in resonance, regardless of particle size. Thus, one expects to observe resonant tunneling effects only near zero applied field in systems containing a distribution of magnetic sizes.Horse-spleen ferritin is in many ways an ideal laboratory for searching for resonant tunneling. It is a superparamagnet that consists of an iron-storage protein with an antiferromagnetic core of diameter Ͻ8 nm such as ͑FeOOH͒ 8 ͑FeOPO 3 H 2 ). Although the magnetic cores are broadly distributed in size in natural ferritin, the maximum cluster size is limited by the volume of the protein cage; moreover, since each is contained within a protein molecule, the interaction between clusters is relatively small. Also, because ferritin is antiferromagn...

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“…[51] [52] [53] Likewise, the chemistry of alkylidynetricobalt nonacarbonyl cluster compounds, (CO) 9 Co(µ 3 -CR), has been extensively investigated since the appearance of the first member of this class of compounds, (CO) 9 Co 3 (µ 3 -CCH 3 ) in 1958.…”

Section: Xinjian Lei: After Graduating With His Ms From the Fujian mentioning

confidence: 99%

Clusters as Ligands – Large Assemblies of Transition Metal Clusters

Lei¹,

Wolf

Fehlner³

1998

Eur. J. Inorg. Chem.

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A strategy of using functionalized clusters as ligands for cationic metal centers facilitates the construction of designed transition metal cluster assemblies. Examples of cluster metal carboxylates with conventional as well as novel structures are given and an application of these large molecular species to the generation of heterogeneous hydrogenation catalysts with unusual activities and selectivities is described.

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Resonant magnetization tunnelling in the half-integer-spin single-molecule magnet [PPh4][Mn12O12(O2CEt)16(H2O)4]

Cited by 72 publications

References 15 publications

A Wheel‐Shaped Single‐Molecule Magnet of [Mn^II₃Mn^III₄]: Quantum Tunneling of Magnetization under Static and Pulse Magnetic Fields

A Wheel‐Shaped Single‐Molecule Magnet of [Mn^II₃Mn^III₄]: Quantum Tunneling of Magnetization under Static and Pulse Magnetic Fields

Anomalous magnetic relaxation in ferritin

Clusters as Ligands – Large Assemblies of Transition Metal Clusters

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Resonant magnetization tunnelling in the half-integer-spin single-molecule magnet [PPh4][Mn12O12(O2CEt)16(H2O)4]

Cited by 72 publications

References 15 publications

A Wheel‐Shaped Single‐Molecule Magnet of [MnII3MnIII4]: Quantum Tunneling of Magnetization under Static and Pulse Magnetic Fields

A Wheel‐Shaped Single‐Molecule Magnet of [MnII3MnIII4]: Quantum Tunneling of Magnetization under Static and Pulse Magnetic Fields

Anomalous magnetic relaxation in ferritin

Clusters as Ligands – Large Assemblies of Transition Metal Clusters

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A Wheel‐Shaped Single‐Molecule Magnet of [Mn^II₃Mn^III₄]: Quantum Tunneling of Magnetization under Static and Pulse Magnetic Fields

A Wheel‐Shaped Single‐Molecule Magnet of [Mn^II₃Mn^III₄]: Quantum Tunneling of Magnetization under Static and Pulse Magnetic Fields