Arrott-Noakes plots near the Curie temperature of Fe3Pt: Ordered and disordered alloys in high magnetic fields

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Abstract
Arrott and Noakes have proposed the following equation of state for the magnetization near the Curie temperature: M1/β = A(T−TC)+B(H/M)1/γ⋅⋅⋅(1), where 1/β = 2.5 and 1/γ = 0.75. In the present report, the M2.5 vs (H/M)0.75 plots (A‐N plots) for ordered and disordered Fe72Pt28 alloys are examined in order to clarify the relationship between the magnetic homogeneity and the structural order parameter S. The A‐N plots for the alloys with S = 0 and 1 lie on parallel straight lines, being satisfactorily expressed by Eq. (1), since the ideally disordered alloy is magnetically homogeneous as well as the perfectly ordered alloy. On the other hand, the magnetizations of the alloys with 0<S<1 are not fitted to Eq. (1). It is likely that the deviation from the linearity of the A‐N plots is a reliable criterion of the magnetic inhomogeneity.