High-temperature critical susceptibility of gadolinium

Low-field ac critical magnetic susceptibility measurements on a variety of toroidal samples of polycrystalline gadolinium are reported. The use of transient enhancement and temperature modulation of the ac susceptibility in bulk studies of critical magnetic behavior is discussed. Consistent values of $\gamma =1.24\mathrm{}\pm 0.02$ and ${\chi }_0=0.0105\mathrm{}\pm 0.0005$ (relative susceptibility) are obtained for samples of varying purities and using different analytical techniques. The observation of a well-defined temperature range of ∼7 K for critical behavior in ∼99-wt.% pure samples and in low (<130 A ${\mathrm{m}}^{-1\mathrm{}}$) magnetic fields is consistent with recent theoretical studies of the effects upon critical magnetic susceptibility of a distribution in ordering temperature and demagnetizing fields.