Hyeong-Cheol Ri

Novel 48-membered hexadecanuclear and 60-membered icosanuclear manganese metallamacrocycles.

Either an S 8 symmetrical 48-membered hexadecanuclear or an S 10 symmetrical 60-membered icosanuclear manganese metallamacrocycle was self-assembled using a manganese ion and a ditopic pentadentate ligand. This was either N-4-phenylbenzoylsalicylhydrazide (H 3pbshz) containing a rigid rod-shaped, bulky biphenyl residue as a terminal N-acyl group or N-3,3-diphenylpropionylsalicylhydrazide (H 3dppshz) containing a flexible beta-branched N-acyl group, but with two sterically bulky phenyl residues at the Cbeta position. The backbone of these metal-organic assemblies is a repeating unit consisting of a -[Mn-N-N-] link that extends to complete either the 48-membered cyclic structure involving 16 manganese(III) centers and 16 ditopic linker ligands or the 60-membered cyclic structure involving 20 manganese(III) centers and 20 ditopic linker ligands (depending on the ligand used). Even though the nuclearity of the metallamacrocycles was different, the successive manganese centers were in the same chiral sequence, ...(LambdaLambdaDeltaDelta)(LambdaLambdaDeltaDelta)....

Steric control of the nuclearity of metallamacrocycles: formation of a hexanuclear gallium metalladiazamacrocycle and a hexadecanuclear manganese metalladiazamacrocycle†‡

An S6-symmetric hexanuclear gallium metalladiazamacrocycle, [Ga(III)(6)L2(6)S6] with a -(lamda delta)(lamda delta)-chiral sequence and an S-symmetric hexadecanuclear manganese metalladiazamacrocycle, [Mn(III)(16)L2(16)S16] with a -(lamda lamda delta delta)(lamda lamda delta delta)-chiral sequence were prepared using the same N2-trans-cinnamoyl-2-hydroxy-3-naphthoylhydrazide (H3L2) as a bridging pentadentate ligand between the metal centers for the formation of a macrocyclic system.

The Relation Between Local Hysteresis Losses and Remanent Magnetic Fields in HTSC Films

Various critical state models have been developed to understand the hysteresis loss mechanism of high-temperature superconducting (HTSC) films. The analytic relation between the hysteresis lossx and the remanent field was obtained based on Beans critical state model for thin films in the full-penetration case. Furthermore, numerical calculation of local hysteresis loops was carried out by Kims critical state model. In this paper, we investigated local hysteresis losses for a GdBCO coated conductor by using low-temperature scanning Hall probe microscopy and reproduced the experimental results by applying the critical state model. Because of the demagnetizing effect in thin films, analysis of local hysteresis losses can be useful approach to understand of total hysteresis losses.

Local Magnetization Measurements on GdBCO Coated Conductors With Narrow Strands: A Comparative Study

The local magnetization of the GdBCO coated conductors was investigated with external magnetic fields applied parallel to the c-axis by using low-temperature scanning Hall probe microscopy. The GdBCO coated conductors were patterned to be bridge shapes by photolithography method. The experimental results are in quantitatively good agreement with the modified Beans critical state model. In addition, the normalized local hysteresis loss was justified to be accordant to the normalized remanent field distribution.