En-Che Yang

Cobalt single-molecule magnet

A cobalt molecule that functions as a single-molecule magnet, [Co4(hmp)4(MeOH)4Cl4], where hmp− is the anion of hydroxymethylpyridine, is reported. The core of the molecule consists of four Co(II) cations and four hmp− oxygen atom ions at the corners of a cube. Variable-field and variable-temperature magnetization data have been analyzed to establish that the molecule has a S=6 ground state with considerable negative magnetoanisotropy. Single-ion zero-field interactions (DSz2) at each cobalt ion are the origin of the negative magnetoanisotropy. A single crystal of the compound was studied by means of a micro-superconducting quantum interference device magnetometer in the range of 0.040–1.0 K. Hysteresis was found in the magnetization versus magnetic field response of this single crystal.

Exchange bias in Ni4 single-molecule magnets

Abstract The syntheses and physical properties are reported for three single-molecule magnets (SMMs) with the composition [Ni(hmp)(ROH)Cl]4, where R is CH3 (complex 1), CH2CH3 (complex 2) or CH2CH2C(CH3)3 (complex 3) and hmp− is the monoanion of 2-hydroxymethylpyridine. The core of each complex is a distorted cube formed by four NiII ions and four alkoxide hmp− oxygen atoms at alternating corners. Ferromagnetic exchange interactions give a S=4 ground state. Single crystal high-frequency EPR spectra clearly indicate that each of the complexes has a S=4 ground state and that there is negative magnetoanisotropy, where D is negative for the axial zero-field splitting DŜz2. Magnetization versus magnetic field measurements made on single crystals with a micro-SQUID magnetometer indicate these Ni4 complexes are SMMs. Exchange bias is seen in the magnetization hysteresis loops for complexes 1 and 2.

Quantum superposition of high spin states in the single molecule magnet Ni4

Magnetic quantum tunneling in a single molecule magnet (SMM) has been studied in experiments that combine microwave spectroscopy with high sensitivity magnetic measurements. By monitoring spin-state populations in the presence of microwave magnetic fields, the energy splittings between low lying high spin superposition states of SMM Ni

High-frequency electron paramagnetic resonance investigations of tetranuclear nickel-based single-molecule magnets

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Half-Integer Spin Heptanuclear Single-Molecule Magnet with an Unusual MnIII6MnII Exchange-Coupled Core

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Origin of the fast magnetization tunneling in the single-molecule magnet [Ni(hmp)(t-BuEtOH)Cl]4

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Electronic structure and magnetic anisotropy for nickel-based molecular magnets

= 4) have been measured. Absorption linewidths give an upper bound on the rate of decoherence. Pulsed microwave experiments provide a direct measure of the spin-lattice relaxation time, which is found to be remarkably long (

Inhomogeneous broadening of single photon transitions in molecular magnets

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Structural, Spectroscopic, and Theoretical Investigation of a T-Shaped [Fe3(μ3-O)] Cluster

sec) and to increase with the energy splitting.

Fast Magnetization Tunneling in Tetranickel(II) Single-Molecule Magnets

We report preliminary high-frequency electron paramagnetic resonance (EPR) investigations for several tetranuclear nickel complexes which exhibit single-molecule magnetism, including low-temperature (below ∼1 K) hysteresis loops and resonant magnetic quantum tunneling. The combination of a cavity perturbation technique and a split-coil magnet facilitates high-sensitivity, multifrequency (40 to 200+ GHz), angle dependent single-crystal EPR measurements. The data confirm the expected S=4 ground states, and a negative magnetocrystalline anisotropy for each member in the series. An unusual splitting of the easy-axis EPR peaks is observed, which may be interpreted in terms of distinct Ni4 species within the crystals. Overall, however, the trends associated with the splitting, as well as the EPR linewidths and shapes, suggest that intermolecular exchange interactions are important. Indeed, differences between the EPR spectra obtained for different complexes correlate nicely with the expected strength of exchang...