Magnetostriction in Nickel Ferrite and Cobalt—Nickel Ferrite

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Abstract
The magnetostriction constants λ100 and λ111 for nickel ferrite have been measured using a ferromagnetic resonance technique which also permits measurements of linewidth, g factor, and anisotropy on the same sample. Our measurements show that all of these parameters are essentially temperature independent from 4° to 300°K in contrast to the behavior of other ferrites. The magnetostriction results are: λ100=−46×10−6, λ111=−22×10−6 at room temperature with less than a 20% variation from these values down to 4°K. The temperature independence of the linewidth and its magnitude (∼20 Oe) both indicate an absence of the ferrous ions which have complicated measurements by some other investigators. Measurements have also been made of the magnetostriction of Co0.05Ni0.95Fe2O4 over the range ∼100° to 300°K. At room temperature both λ100 and λ111 have approximately the same values as in NiFe2O4, but at lower temperatures the cobalt contribution causes |λ111| to increase sharply while |λ100| is relatively unaffected. This behavior is qualitatively in agreement with a theory by Slonczewski for the similar problem of Co2+ in magnetite. The sign of λ111, however, is different in the two materials. Linewidth in the three principal directions in Co0.05Ni0.95Fe2O4 has also been measured.