Magnetic crystal anisotropy and magnetostriction have been measured in various single crystals of ferrites having compositions represented approximately by $M{\mathrm{Fe}}_2{\mathrm{O}}_4$, where $M$ stands for Mn, Fe, Co, Ni, and Zn in various proportions. Special attention is given to heat-treatment in a magnetic field.

The magnetic anisotropy of cobalt ferrite at room temperature is as high as 4×${10}^6$ ergs/${\mathrm{cm}}^2$. Magnetostriction is as high as 800×${10}^{-6\mathrm{}}$. Magnetic anneal is effective at temperatures as low as 150°C, and causes the hysteresis loop to become square. In polycrystalline material the response to magnetic anneal is a maximum at compositions intermediate between Co${\mathrm{Fe}}_2$${\mathrm{O}}_4$ and ${\mathrm{Fe}}_3$${\mathrm{O}}_4$.

The constants for the various specimens are tabulated. Values of the anisotropy constants of Mn${\mathrm{Fe}}_2$${\mathrm{O}}_4$ at 20°C and -196°C are the same as those determined from ferromagnetic resonance experiments. At -196°C the constant for ${\mathrm{Ni}}_{0.75}$${\mathrm{Fe}}_{2.25}$${\mathrm{O}}_4$ differs markedly from that determined by ferromagnetic resonance; this is to be expected from the relaxation phenomena observed by Galt, Yager, and Merritt.

• Received 12 May 1955

DOI:https://doi.org/10.1103/PhysRev.99.1788