Magnetocrystalline Anisotropy of Low Temperature Phase of Magnetite

概要

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The magnetocrystalline anisotropy of low temperature phase of magnetite (Fe_3O_4) was measured for a monoclinic single phase specimen by using computerized fully-automatic torque magnetometer. The anisotropy is expressed by E_a=K_aα^2_a+K_bα^2_b+K_<aa>α^4_a+K_<bb>α^4_b+K_<ab>α^2_aα^2_b-K_uα^2_<111>, where α_a, α_b and α_<111> 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 calues of the anisotropy constants at 4.2 K arc: K_a=25.5, K_b=3.7, K_u=2.1, K_<aa>=1.8, K_<bb>=2.4 abd K_<ab>=7.0 in 10^5 erg/cm^3. It was found that K_a, K_b and K_u exhibit the temperature dependence of an activation type with the activation energy of about 0.02 eV. It was also found that the constants K_<aa>, K_<bb> and K_<ab> are well expressed in terms of cubic K_1. The mechanism of the anisotropy is also discussed.
社団法人日本物理学会の論文
1976-12-15