Reentrant Spin-Glass Behavior in Cobalt(II) Based Coordination Polymers

Correlation of molecular structure and its magnetic property gives a better understanding toward the design of magnetic materials with long-range magnetic order. Here we report two new cobalt-based coordination polymers that exhibited coexistence of long-range ferromagnetic (FM) order and spin-glass (SG) transition at below T_c. Different orientation of magnetic moments, arrangements, and variation in connectivity with the ligands might be responsible for the SG transition. The SG transition was characterized by bifurcation of zero-field-cooled and field-cooled splitting at T_f ≈ 9.9 K (for both compounds) and AC susceptibility measurements. DC magnetization revealed the FM transition at high temperature, followed by a low-temperature SG transition. Moreover, the peculiarity found in low-temperature χ′′(T) can be attributed to the complex interplay between antiferromagnetic and ferromagnetic interactions and the coexistence of the long-range FM order and SG phase. Optical bandgap and temperature-dependent resistivity measurements showed that these compounds are semiconducting in nature.