Low temperature relaxation crossover in one dimensional chain-like molecular magnet [Fe$^{II}(\Delta)$Fe$^{II}(\Lambda)$(ox)$_{2}$(phen)$_{2}$]$_{n}$

The frequency-dependent ac susceptibility, thermoremanent magnetization relaxation (TRM) and magnetic field dependent magnetization have performed on a hand-aligned partially orientated molecular magnet compound [Fe$^{II}(\Delta )$Fe$^{II}(\Lambda )$(ox)$_{2}$(phen)$_{2}$]$_{n}$,[1] which exhibits one dimension chain like structure. The ac susceptibility shows spin glass-like relaxation at temperatures between 7.8 and 8.2 K. In addition, the TRM results show various relaxation behaviors below T$_{m}$ $\sim $ 8.6 K, indicating that there is a remnant instability at low temperature. It might be caused by the complex interaction within and/or between the chains and the stacked layers. With slowly sweeping the magnetic field, a step-like behavior in the magnetic hysteresis loop was observed below T$_{m}$. The possible origins for these properties are discussed. \newline [1] L. L. Li, K. J. Lin, C. J. Ho, C. P. Sun, and H. D. Yang, Chem. Commun. \textbf{12}, 1286 (2006).