The 21/3 rule for magnetic susceptibility of gadolinium

The dependences of the magnetization M and the magnetic susceptibility χ = ∂M/∂H of pure gadolinium (the concentration of foreign impurities is lower than 0.1 wt %) on the temperature T and the magnetic field H have been measured using a Quantum Design MPMS-5XL SQUID magnetometer. In this material, inhomogeneities of the atomic structure should not lead to a nonuniform distribution of the magnetic characteristics (including the Curie temperature TC) over the volume of the sample. The obtained dependences of M and χ have been used to investigate the possibility of suppressing magnetic inhomogeneities of other types by magnetic fields with a strength of up to 50 kOe. It has been assumed that these inhomogeneities are suppressed when the specific relationship, namely, the 21/3 rule is fulfilled. The rule relates the portions of the dependence χ(T, H) which at the temperature T = TC and at the maximum in the curve χ(T) (T = Tm) depend on H in accordance with the H2/3 law. It has been shown that the portions separated from the experimental curves χ(TC, H) and χ(Tm, H) obey the 21/3 rule.