= Tricritical heat-capacity amplitude in a sextic Landau expansion
{title2=$C_{\mathrm{sing}}=Tb^{3/2}(T_c-T)^{-1/2}/(2\sqrt{3d'})$}
For $F=F_0+b(T-T_c)M^2+d'M^6$ with $b,d'>0$, the ordered minimum has $M^4=b(T_c-T)/(3d')$. Its singular <free energy> is $-2b^{3/2}(T_c-T)^{3/2}/\sqrt{27d'}$. Twice differentiating in <temperature> gives the displayed ordered-side <heat capacity> singularity, with mean-field <critical exponent> $\alpha=1/2$. This path keeps the quartic coefficient tuned to zero; a generic path with a positive quartic term instead crosses over to the ordinary quartic result.
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