Thermal dependence of magnetocrystalline anisotropy and magnetostriction constants of single crystal Fe_2,4Ti_0.61O₄

The temperature dependence of the magnetocrystalline anisotropy (K′) and magnetostriction (λ) constants of single crystal Fe_2.4Ti_0.61O₄ (TM61) is measured using torque magnetometry and strain gage techniques in the temperature range between 300 K and T_c. At all temperatures, K′ is positive making the <100> instead of <111> crystal directions the easy axes of magnetization in TM61. The thermal dependence of K′(T) varies as (1‐T/T_c)^2.2. In terms of the saturation magnetization, K′(T)∝M_s(T)ⁿ where n≈6, a much weaker dependence than that found for magnetite (n=8–10). We also observed that K′∝λ^1–2, consistent with K′∝M_s⁶. These results show that the magnetoelastic contribution to the magnetocrystalline anisotropy dominates the anisotropy constant of TM61 at elevated temperature and that the effects of stress cannot be neglected in theories of thermoremanence and micromagnetic models for intermediate titanomagnetites commonly found in oceanic basalts.