Contribution of Fe²⁺ ions to the magnetocrystalline anisotropy constant K₁ of Fe_3-xTi_xO₄ (0<x<0.1)

The magnetocrystalline anisotropy constant K₁ of Fe₃O₄, Fe_2.96Ti_0.04O₄ and Fe_2.9Ti_0.1O₄ has been measured between room temperature and the Curie point using the torque method. The Fe³⁺ contribution to the anisotropy in this temperature range has been calculated using the theory of Wolf (1957) and the relative sublattice magnetizations determined from Mossbauer-effect spectra. The specific Fe²⁺ contribution, K^2B₁ is then found to vary with composition x and temperature T as K₁^2B(x,T)= (0.2-3.5X) * 10^-2-(0.24+3.0x)(T_c-T)^10/3 * 10^-8 cm^-1/ion.