It is my understanding that the observed magnetic susceptibility (Xobs) of a material from SQUID magnetomtery data (MvT) is composed of several components
Xobs = Xpara + Xdia + Xtip
Where the paramagentic contribution (Xpara) is the key part to Curie/Curie Weiss law and for calculating the effective magnetic moment of a material. Thus the Diamagnetic contribution (Xdia) and Temperature independent paramagnetism contribution (Xtip) must be accounted for and subtracted from the Xobs in order to have an accurate description of the unpaired electrons.
The diamagnetic contribution (Xdia) from the electrons in the core orbitals can subtracted from the observed molar susceptibility by calculating from Pascals constants.
It my understanding plotting Xobs vs 1/T of a paramagnetic material will give Xtip as the intercept of the Y-axis i.e. X = C*1/T + Xtip, and thus one can easily subtract and get a nice curie plot and further calculate the effective magnetic moment.
However, I am unsure how to find/subtract the Xtip from an antiferromagnetic (or ferromagnetic for that matter) material without loosing the Weiss Constant (W). Surely if one subtracts the Y intercept then W=0 when we plot 1/Xp vs T.... what is the usual procedure for subtracting this so that one can accurately calculate W and more importantly the effective magnetic moment.....
Well, you would have first to think about whether your sample does actually possess a temperature independent paramagnetic contribution and where that derives from. If for example you had a thin film on a substrate which contains paramagnetic impurities, then you are likely to have an undesired paramagnetic contribution to your magnetometer signal but that will usually not be temperature independent!!
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