The Absolute Saturation of Cubic Cobalt

With an ellipsoid of cobalt, quenched so as to be in the cubic state, and Weiss' method of extracting the ellipsoid from the field of a powerful electromagnet, the magnetization was measured for a given temperature but increasing field strengths. With Weiss' formula for the approach to saturation the magnetization for infinite field was calculated. The Weiss formula fitted the upper half of the experimental curve within 0.03 percent. When the saturation magnetizations, ${\mathrm{J}}_{\mathrm{ST}}$, obtained for 13 temperatures were plotted against the square of the absolute temperature a straight line was obtained. When this was extrapolated to absolute zero the saturation intensity (${\mathrm{J}}_{\mathrm{SO}}$) was found to be 1418. By plotting $\frac{{\mathrm{J}}_{\mathrm{ST}}}{{\mathrm{J}}_{\mathrm{SO}}}$ against ${\left(\frac{\mathrm{T}}{\theta }\right)}^2$, $\theta$ being the Curie point, the line obtained coincided with that for iron and nickel, but not with the curve for hexagonal cobalt nor the line found for orthorhombic crystals. It is indicated that crystal structure plays an important part in ferromagnetism.