Magnetic Susceptibility of Metallic Europium

Abstract

The susceptibility of europium is measured from 1.3 to 300°K in fields up to 12 000 oersteds. This metal is found not to be ferromagnetic, but to have at low temperatures a very high paramagnetic susceptibility, about forty times higher than for the free ion or hydrated salts. Variation of susceptibility with field strength is observed below 100°K. The saturation curvature at low temperatures is very large, and practically independent of temperature. The susceptibility at high temperatures is consistent with a divalent model. The magnetic behavior at low temperatures is hard to interpret on the basis of a divalent ion and can be more readily explained with a trivalent one for which the theory is developed. Metallurgical evidence, however, indicates that metallic europium is divalent even at low temperatures. On the other hand, it is generally believed that europium is trivalent in Eu${\mathrm{Ir}}_2$, but if one uses the conventional molecular field theory the reported ferromagnetism of Eu${\mathrm{Ir}}_2$ cannot be ascribed to ${\mathrm{Eu}}^{+++}$ with a value of the exchange field consistent with that in Gd${\mathrm{Ir}}_2$.