Did u perform the analysis it in-situ or after thermal treatment?

Dear Maykel, 

Thanks for your response.  I didn't carry out the measurement by myself.  But the measurement was carried out using SQUID,  usually you just mount the sample on stage and use helium system to regulate the temperature.  

So, basically data for magnetization were collected using the same scan rate at different temperatures.  For example,  the temperature is set at say 1 K and the magnetization versus field is measured by scanning the field over a certain field range (say 0-5T). After the first scan,  the second scan is performed at 2 K, then 3 K etc.  So, it is expected that as you increase the temperature,  the hysteresis loop should start closing up or the area bound by the loop should diminish.  However,  in this case, the hysteresis loop was opening the more with increasing temperature.  This is unusual and so I really can't think of a possible reason that could lead to this.  

I hope you understand the problem now.  

Thank you. 

Dear David, I got the point. It might because of low temperature soft magnetic phase. There'll be a magnetic transition at higher temperature before the coercivity decrease as a function of temperature.

It'll be interesting if u cud perform in-situ neutron diffraction.

Dear Maykel,

Thanks once more. Unfortunately, I do not have access to any one that can help with the neutron diffraction. However, I am wondering on what possible information regarding this phenomenon can one get from neutron diffraction.

You suggested it might be due to low temperature soft magnetic phase. If I get your right, are you suggesting that magnetization curve that shows increasing coercivity with decreasing temperature has a temperature range below which this relationship is not feasible?

With regards to single-molecule magnets, magnetic data are all obtained at helium temperature and they also show the normal relationship with temperature even at an ultra low temperature in milikelvin. 

Hence, it is a bit difficult to comprehend the low temperature soft magnetic phase you talked about. Do you have any reference that I could read on this? I would appreciate if you could send me a link or any material that could help. Thank you very much for your contributions as I await more of it.

I can imagine (but I have never seen it) that such a behavior might happen for ferrimagnetic materials around the so called compensation point, i.e. such temperature (below Neel critical temperature) at which the two sublattices produce null net spontaneous magnetization (in absence of external field).

Dear David,

Sorry for the late reply. Her is one of the article that mentioned about what i stated above.

"Magnetic Characteristics for the Mould-Cast Hard Magnetic Nd70−xFe30Alx (x = 0–10) Alloys" 10.1109/TMAG.2015.2422671

Dear Prof. Marek Wojciech Gutowski,

Thank you so much for your contribution. I think you have a point there because, from the XmT vs T, there seem to be some kinda antiferromagnetic coupling but it is very weak. However, there are numerous compounds that also show such interaction at such low temperature yet they didn't show this phenomenon. I will consider this possibility as I look further. Thank you.

Thank you  Maykel,

You have been indeed helpful. I just accessed the article. I will go through it I really appreciate. Thanks again.