Variation of the Magnetic Properties of Barium with Temperature

A discontinuity in the resistivity-temperature curve for pure barium at about 370°C has led to the suggestion that two modifications of the crystal structure ($\alpha$ and $\beta$-barium) exist, below and above this temperature respectively. Further, the similarity of the curve to that for the ferromagnetics makes it reasonable to suppose that a discontinuity in the susceptibility-temperature curve (i.e., a Curie point) may exist. The susceptibility has been measured over a range of 400°C and such a discontinuity is found to exist at about 350°C. The experimental results are completely at variance with the current theory for paramagnetics.