title: Structural tailoring effects on the magnetic behavior of symmetric and asymmetric cubane-type Ni complexes.
abstract: Using two kinds of carboxylate ligands with small but significant differences in steric size, symmetric and asymmetric Fe(II) and Ni(II) cubanes have been synthesized in a controlled fashion. Fast sweeping pulsed field measurements showed magnetization hysteresis loops for two cubane-type molecular complexes, [Ni4(μ-OMe)4(O2CAr(4F-Ph))4(HOMe)8] and [Ni4(μ-OMe)4(O2CAr(Tol))4(HOMe)6], thus suggesting single-molecule magnet behavior. To differentiate the magnetic properties between the symmetric and asymmetric cubanes, detailed electron paramagnetic resonance (EPR) measurements were performed. From the EPR data, taken at various frequencies and temperatures, zero-field splitting parameters D, E, and other higher-order parameters for both cubane samples were extracted. Compared to the symmetric Ni-cubane, the asymmetric one shows an increase in the D and E values by about 20%, thereby suggesting structural engineering effects on the magnetic properties. By using the magnetic parameters determined by EPR, a static magnetization curve at 2 K and a temperature dependence of the magnetic susceptibility were simulated. A good agreement between theoretical and experimental data confirms the validity of the values obtained from EPR measurements.
authors.affiliation: Department of Physics, Chung-Ang University, 221 Huksuk-Dong, Seoul 156-756, Republic of Korea.
authors.forename: Alexey N
authors.initials: AN
authors.lastname: Ponomaryov
authors.forename: Namseok
authors.initials: N
authors.lastname: Kim
authors.forename: Jaewon
authors.initials: J
authors.lastname: Hwang
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nojiri
authors.forename: Johan
authors.initials: J
authors.lastname: van Tol
authors.forename: Andrew
authors.initials: A
authors.lastname: Ozarowski
authors.forename: Jena
authors.initials: J
authors.lastname: Park
authors.forename: Zeehoon
authors.initials: Z
authors.lastname: Jang
authors.forename: Byoungjin
authors.initials: B
authors.lastname: Suh
authors.forename: Sungho
authors.initials: S
authors.lastname: Yoon
authors.forename: Kwang-Yong
authors.initials: KY
authors.lastname: Choi