 Arrott plot

An Arrott plot presents squared magnetisation against field divided by magnetisation. For the uniform SI Landau equation ${\mu }_{0}H=aM+b{M}^3$, it is a straight lineThe critical mean-field isotherm has $a=0$ and passes through the origin. Horizontal intercept $a/{\mu }_0$ changes sign across the transition; a positive vertical intercept estimates spontaneous magnetisation squared. The original criterion concerns internal magnetic field and the molecular-field regime. Demagnetizing fields and non-mean-field critical exponents require additional care.^[ref]

An Arrott plot is a graphical method used in the analysis of magnetic materials, specifically to study the properties of ferromagnets and their phase transitions. It is named after the scientist William Arrott, who contributed significantly to the understanding of magnetic behavior in materials.