Arrott plot

In condensed matter physics, an Arrott plot is a plot of the square of the magnetization M 2 {displaystyle M^{2}} of a substance, against the ratio of the applied magnetic field to magnetization H / M {displaystyle H/M} at one (or several) fixed temperature(s). Arrott plots are an easy way of determining the presence of ferromagnetic order in a material. They are named after American physicist Anthony Arrott who introduced them as a technique for studying magnetism in 1957. In condensed matter physics, an Arrott plot is a plot of the square of the magnetization M 2 {displaystyle M^{2}} of a substance, against the ratio of the applied magnetic field to magnetization H / M {displaystyle H/M} at one (or several) fixed temperature(s). Arrott plots are an easy way of determining the presence of ferromagnetic order in a material. They are named after American physicist Anthony Arrott who introduced them as a technique for studying magnetism in 1957. According to the Ginzburg-Landau mean field picture for magnetism, the free energy of a ferromagnetic material close to a phase transition can be written as: F ( M ) = − H M + a T − T c T c M 2 + b M 4 + … {displaystyle F(M)=-HM+a{frac {T-T_{c}}{T_{c}}}M^{2}+bM^{4}+ldots } where M {displaystyle M} , the magnetization, is the order parameter, H {displaystyle H} is the applied magnetic field, T c {displaystyle T_{c}} is the critical temperature, and a , b {displaystyle a,b} are material constants.