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Origin of the fast magnetization tunneling in tetranuclear nickel single-molecule magnets |
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| Affiliation: | 1. Department of Chemistry and Biochemistry-0358, University of California at San Diego, La Jolla, CA 92093-0358, USA;2. Department of Physics, University of Florida, Gainesville, FL 32611, USA;3. Institute of Solid State Physics, The University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8581, Japan;4. Laboratoire Louis Néel-CNRS, 25 Avenue des Martyrs, 38042 Grenoble Cedex 9, France;5. Department of Chemistry, Florida State University, Tallahassee, FL 32606, USA;6. Department of Chemistry, One Shields Avenue, University of California at Davis, Davis, CA 95616, USA;1. INSERM U1148, Laboratory for Vascular Translational Science (LVTS), Institut Galilée, Université Paris 13, Sorbonne Paris Cité, 99 Avenue Jean-Baptiste Clément, Villetaneuse, F-93430, France;2. Inserm U1148, Laboratory for Vascular Translational Science, UFR SMBH, Université Paris 13, Sorbonne Paris Cité, Groupe Biothérapies et Glycoconjugués, Bobigny, F-93430, France;1. School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore;2. PVD Department of Plating Division, Singapore Epson Industrial Pte Ltd, Singapore 628162, Singapore;3. Department of Materials Engineering, Ming Chi University of Technology, Taipei 24301, Taiwan, ROC;4. Center for Thin Film Technologies and Applications, Ming Chi University of Technology, Taipei 24301, Taiwan, ROC;5. Analysis and Testing Center, Soochow University, Suzhou 215123, China;6. School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore;7. Central Iron and Steel Research institute, 76 South Xueyuanlu Road, Haidan District, Beijing 100081, China;1. Department of Inorganic Chemistry, Chemical Faculty, Gdańsk University of Technology, Narutowicza 11/12, 80-233 Gdańsk, Poland;2. Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland |
| Abstract: | Several tetranuclear nickel(II) single-molecule magnets (SMMs) have been prepared with the general composition of [Ni(hmp)(ROH)X]4 · S, where hmp− is the monoanion of 2-hydroxymethylpyridine, X− is either Cl− or Br− and S is the solvate molecule. Magnetization versus magnetic field hysteresis loops for these Ni4 SMMs show that there is a relatively fast rate of magnetization tunneling (small coercive field) and, in certain cases, an exchange bias present. Detailed measurements have been carried out in order to determine the origin of the fast magnetization tunneling. High-field electron paramagnetic resonance (HFEPR) data were collected on a single crystal of [Zn(hmp)(dmb)Cl]4 doped with a small amount of Ni(II), where, dmb is 3,3-dimethyl-1-butanol. These variable-frequency/temperature data give values of the single-ion zero-field splitting parameters Di and Ei, and the orientations of these interactions, for the single NiII ions in a Zn3Ni complex doped into a Zn4 crystal. HFEPR data were also obtained at many frequencies and temperatures for a single crystal of isostructural [Ni(hmp)(dmb)Cl]4. Rotation of the single crystal such that the external field is positioned in the hard plane clearly establishes that the transverse zero-field interaction is the cause of the fast magnetization tunneling in the S = 4 ground state of this SMM. The magnitude of and the Ni4 D value can be related to the directionality and magnitude of the Di and Ei interactions at the individual NiII ions, determined for the doped crystal. The microenvironments and ligand dynamics were probed by means of a single-crystal X-ray structure at 12 K and by heat capacity data. |
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