PHYSICS/BK21 Colloquium

Molecular Nanomagnetic Systems Exhibiting Exotic Magnetic Properties

연사: 홍창섭[고려대]

일시: 2007 년 5 월 18 일 오후 3시

장소: 무은재 기념관 307호 (멀티미디어 강의실)

ABSTRACT:

The research on single-molecule magnets (SMMs) and singe-chain magnets (SCMs) has attracted intensive attention due to intriguing physical properties associated with quantum tunnelling of magnetization effects within double energy well and potential applications to high-density information storage. Since the slow magnetization relaxation in [Mn12O12(CH3COO)16(H2O)4] (Mn12ac) was discovered much effort has been made to fabricate metal-oxo clusters with the aim of generating analogous properties to the archetype Mn12 cluster. Recently, a giant Mn84 cluster with a diameter of ~4 nm was characterized structurally and magnetically, exhibiting SMM behaviour. Despite the high nuclearity in the Mn84 supramolecular nanotube its ground state (S) and energy barrier (U) remain relatively small compared with the Mn12ac cluster.

To design such systems it would be beneficial if a bridging ligand has structural and magnetic predictabilities. Cyanide is one of the good candidates as a bridge for magnetic entities since it links paramagnetic centers in a linear fashion and the magnetic nature of compounds bridged by cyanides is dependent on magnetic orbitals of metal constituents. Cyanide-linked magnetic systems have successfully realized a variety of structures from zero-dimensional (0D) to 3D networks with intriguing multifunctional properties. Recently, because of increasing interests in isolated anisotropic systems, main emphasis has been on fabricating discrete or 1D systems to employ molecular precursors with ample coordinating capability, for instance, [M(CN)p]n- (p = 6, 8), and their counterparts having specific vacant sites or labile leaving ligands, [M’LxL’y]m+ (L = polydentate ligand, L’ = labile group). Another reliable strategy to this aim has been launched by engaging blocked cyanide-based building bricks for low-dimensional materials. The molecular building units with the 3d metal ions, [M(CN)pLq]n- (M = CrIII, FeIII), have been thoroughly investigated, while examples, [M(CN)pLq]n- (M = MoIII, ReII), which incorporate 4d or 5d metal ions into molecular precursors are still rare to date although the 4d or 5d magnetic orbitals mediate stronger magnetic couplings because they are more diffuse than the 3d magnetic orbitals. In this talk, new cyanide-based SMMs and SCMs containing diverse spin sources will be introduced in terms of their structures and intriguing magnetic properties.

문의처: 지승훈(054-279-2094, jhish@postech.ac.kr)