1976 年 41 巻 6 号 p. 1894-1902
The magnetocrystalline anisotropy of low temperature phase of magnetite (Fe3O4) was measured for a monoclinic single phase specimen by using computerized fully-automatic torque magnetometer. The anisotropy is expressed by
Ea=Kaαa2+Kbαb2+Kaaαa4+Kbbαb4+Kabαa2αb2−Kuα1112,
where αa, αb and α111 are direction cosines of the magnetization with respect to the monoclinic a-, b- and cubic [111] axes, respectively, the last of which coincides with the longest cube diagonal. The values of the anisotropy constants at 4.2 K are: Ka=25.5, Kb=3.7, Ku=2.1, Kaa=1.8, Kbb=2.4 and Kab=7.0 in 105 erg/cm3. It was found that Ka, Kb and Ku exhibit the temperature dependence of an activation type with the activation energy of about 0.02 eV. It was also found that the constants Kaa, Kbb and Kab are well expressed in terms of cubic K1. The mechanism of the anisotropy is also discussed.
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