Currently I am working on the magnetic properties of nanocrystalline perovskite type cobaltites. The below attached graph is showing some unusual magnetic behavior. The ferromagnetic to glassy ferromagnetic propertiy is observed with increasing the applied magnetic field. Moreover, I have measured AC susceptibility for this sample and the peak from the AC susceptibility exactly matches with the curie temperature (Tc) obtained dM/dT curve. And also it follows the frequency independent behavior. Hence it certifies that the ferromagnetic but the attached graph clearly shows that there is a glassy behavior at 1000 Oe and 3000 Oe.
what are all the possible reasons for the ferromagnetic- glassy ferromagnetic transition with increasing field?
Kindly provide me your valuable comments and suggestions to improve my research.
Thanks in advance.
Please find the attached graph
You may want to check out the literature on the reentrant spin glass phenomenon.
No, there is not such possibility. Applying a strong magnetic dc field on a ferromagnetic phase you must reach the saturation magnetization as a constant and with ac field the behaviour is different because you have hysteresis loop given you losses, but never reaching a cluster spin glass phase.
The cluster spin glass phases correspond to the mixture of ferromagnetic clusters interactuating with antiferromagnetic phases within frustated configurations. In the case of having these phases you must have two freezing temperatures (that is convenient that you measure) where the magnetization changes drastically.
In any case it is convenient that you look in the literature.
It is known that the reentrant phenomena from ferromagnetic (FM) to spin glass (SG) is possible, such as in Au-Fe alloys, (Coles et al. 1978), EuxSr1-xS (Maletta 1979, 1982), and Ni-Mn alloys (Abdul-Razzaq and Kouvel 1987) or diluetd CuCrZrS4 (see the attached paper here).
But reeentance from SG to FM phases have yet not observed!
Thus, some questions arise :
-are you sure that your sampe is homogeneous and does not contain several crystalline pahses (such composites)?. For example, if the sample contains a FM phase and a SG, your M(T) curves can be easily explained : at low field the FM would dominates and at high field the two phases contribuate to the magnetization!!
- before coolin your sample in ZFC , are you sure that i was in the virgin state before cooling?
I finish by suggesting to you to make complementary measurments such AC susceptibility (X' and X'' with various frequencies) , specific heat, ..resistivity or magnetresistance.
Good luck
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