An investigation of the “frequency effect” has been made for several nickel ferrous ferrites ([Nix2+ Fe1−x2+ Fe23+]O4, 0.28 ≤ x ≤ 1) by making torque measurements for magnetocrystalline anisotropy on the same arc‐image furnace crystals that were used in the microwave work reported earlier. A plot of &Dgr;k1(k1(torque)‐k1(microwave)) versus the mole fraction of Fe2+shows a curve with maximum occuring for low Fe2+at 170°K. This maximum gradually shifts to higher Fe2+until the variation approaches linearity at 77°K. The &Dgr;k1for these crystals in the temperature range77°K ≤ T ≤ 300°Kare in relatively good agreement with those calculated from Clogston's slow relaxation theory. The calculated relaxation time (&tgr;) was plotted as a function of the mole fraction of Fe2+for several temperatures between 170°K and 77°K. This shows that higher Fe2+yields a lower temperature at which the relaxation process begins and is consistent with the observed &Dgr;k1vs. Fe2+curves.