Electronic Structures and Magnetic Properties of Single-Molecule Magnets (SMMs)

Ishii, Tomohiko; Yamaoka, Yuya: Kudo, Daisuke; Sakane, Genta; Mizuno, Masataka

Single-Molecule Magnet
Study on molecular magnetism has established an important research field in chemistry and physics.  Mono-dispersed superparamagnets, the so-called Single-Molecule Magnets (SMMs), are target materials and they are made of as poly-metal molecular cluster possessing a high spin ground state and a uni-axial anisotropy.  In this paper the molecular structures and the electronic structures of the SMMs are reported.  Of course the SMM materials exhibit not only magnetic properties such as hysteresis of the magnetization but also the quantum effect such as the quantum spin tunneling and the quantum phase interference.  The energy level structures of the SMMs can be explained by means of the double-well potential where two wells correspond respectively to ""spin-up"" and ""spin-down"" states.  The energy barrier is originated from the combination of high spin ground state and an Ising type of magnetic anisotropy.  To date, many examples of SMMs are known: poly-manganese systems such as Mn2, Mn4, Mn8, Mn9, Mn12, Mn16, Mn18, Mn21, Mn22, Mn25, Mn30, and Mn84 clusters, and ones with other metals such as Fe4, Fe8, Fe10, Fe19, V4, Co4, Ni4, Ni12, Ni21, Mn2Cr, Mn2Fe, Mn11Cr, Mn4Re4, MnMo6, Dy6Mn6, CuTb, CuDy, and Mn11Dy4 clusters.  The most important SMM would be [Mn12O12OOAc)16(H2O)4], which is the first molecule to be a SMM and is commonly called ""Mn12-acetate"" or even simple ""Mn12"".  We investigated the ground state and/or excitation states of tetra-nuclear Ni cubane-type complex by DV-Xα molecular orbital calculation, in order to discuss the energy level structures ad the spin states of the SMMs.  As a consequence the SMMs are strongly expected to be applied to high-density information storage devices and the quantum computing elements in near future.
The 4th International Conference on DV-Xα Method, Jeju, South Korea, 3-5 August 2006.
Electronic Structures and Magnetic Properties of Single-Molecule Magnets (SMMs)

Bulletin of the Society for Discrete Variational Xα

Society for Discrete Variational Xα

19

1&2

71

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