What can be found in the MT curves of superconductors?

[Andy Huang]

I am confused about the magnetic susceptibility vs. temperature curves (or MT) of superconductors (SCs).

In the normal conduction state (I measured from 4.5K to 300K), the susceptibility curve can obey the Curie-Weiss law. But when I fitted the data via the Curie-Weiss law in a different temperature range, different results (effective magnetic moment) came out.

How should I select the temperature range in the normal state for fitting the curves with the Curie-Weiss law?

Also, I synthesized a series of SC samples with different Tc. How should I compare the susceptibility curves of SCs with different Tc? What physical properties can be concluded form those MT curves?

 

[AssyriaQ]

A quick question: when you fit, how are you plotting the data? You probably already know this, but you should plot the inverse susceptibility versus temperature. The Curie-Weiss behavior is then a linear relation.

Also, what "different temperature range" did you use?

 

[Andy Huang]

I used the fit function χ=χ0 + C/(T-θ), χ0 =χdia +χPauli = temperature independent contribution.
Taking χ0 into account, I only ploted the susceptibility vs. temperature curve. The temperature range selected for fitting is above the superconducting critical temperature, such as from 50K to 140K, resulting the effective magnetic moment 2.048μB (Fe2+). Another range from 100K to 140K gave 1.842μB.
I upload the data file and appreciate your help for checking it again.

Thanks for helping the novice.