- #1

- 19

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I'm slightly confused about how to prove that:

[tex]\chi[/tex]=[tex]\vartheta[/tex]<M>/[tex]\vartheta[/tex]H

is equal to...

[tex]\chi[/tex]=(<M

^{2}>-<M>

^{2})/ T

I've expressed <M> as [tex]\sum[/tex]M

_{s}exp(-E/k

_{B}T) /

[tex]\sum[/tex]exp(-E/k

_{B}T)

and know that E=-J[tex]\sum[/tex]S

_{i}S

_{j}-H[tex]\sum[/tex]S

_{i}

But seem to get lost in the differentiation. I am going aobut this the correct way?