Memory effect and magnetic relaxation in Ca3Co2O6 and the doped compounds

We report memory effect and magnetic relaxation in spin-chain compounds Ca3Co2O6, Ca3Co2−xTxO6 (T=Mn, Fe, Al, and Mg) with x=0.02 and 0.04, and Ca3−xAxCo2O6 (A=Sr and Na) with x=0.06 and 0.12. The memory effect serves as an evidence of spin-glass-like freezing at low temperatures. The time-dependent magnetization exhibits a nearly exponential variation with time for initial relaxation and is not much influenced by chemical doping. With time goes on, the magnetization follows the stretched exponential function and doping effect gradually appears with uncertainty. In comparison, the influence from Fe-doping is dramatic and possible reason is proposed within the geometrical frustration scenario.