We have measured the ZFC/FC curve under 100Oe, there is splitting happens and there is another turning point happens to around 25K, why it is increased again with decreasing temperature?
Dear Jia Chuang ,
Here, the maxima of ZFC signifies the blocking temperature which is around 100 K in your graph. What happens here is that the thermal energy is able to overcome the energy barrier and this allows the magnetic moments to align with the external magnetic field. Below this temp., the moments are blocked in a particular orientation leading to that peak.
Now, coming to what happens as you see the bifurcation between the ZFC and the FC data as you decreased the temperature. This is widely regarded as the Irreversibility temperature around 60 K in your data, wherein the metastable magnetic states tend to separate from the intrinsic magnetic ordering. This highlights the irreversible magnetic behavior as the metastable states trapped cannot reach equilibrium.
Now, the most general explanation of why are you again getting an increase in susceptibility below the bifurcation can be due to the presence of paramagnetic impurities.
Hope this helps!
Regards,
KP