= Extracting magnetic Landau coefficients from an Arrott plot
{title2=$a=\mu_0X_0,\qquad b=\mu_0/S$}
If physical ordinate is $Y=M^2$ and abscissa $X=H/M$, slope $S=dY/dX$ and horizontal intercept $X_0$ give $b=\mu_0/S$ and $a=\mu_0X_0$. Any displayed squared-magnetisation scale must be converted before using S. For example, an ordinate unit $(10^4\,\mathrm{A\,m^{-1}})^2$ equals $10^8\,\mathrm{A^2\,m^{-2}}$, not $10^4$. With a <free-energy density>, the resulting units are $[a]=\mathrm{H\,m^{-1}}$ and $[b]=\mathrm{J\,m\,A^{-4}}$. <Curvature> or differing isotherm slopes limits the accuracy of a constant-coefficient fit.
Back to article page
