The magnetocrystalline anisotropy constant $K_1$ of iron was determined from static torque measurements on a {001} single-crystal disk at fields between 3000 and 18 000 Oe, and at temperatures between 77 and 900°K. It was found that (i) $\frac{\left(\frac{\partial K_1}{\partial T}\right)}{K_1}\simeq 10\frac{\left(\frac{\partial M}{\partial T}\right)}{M}$ above 300°K, in agreement with Zener; (ii) $\frac{\left(\frac{\partial K_1}{\partial H}\right)}{K_1}\simeq 22\frac{\left(\frac{\partial M}{\partial H}\right)}{M}$ below 600°K, and at $H\simeq 10$ KOe; and (iii) $\frac{\left(\frac{\partial K_1}{\partial H}\right)}{\left(\frac{\partial K_1}{\partial T}\right)}\simeq -1.25\mathrm{}\times {10}^{-3\mathrm{}}°$K/Oe over the whole temperature range of this investigation.

• Received 18 October 1965

DOI:https://doi.org/10.1103/PhysRev.144.372