Effect of magnetic annealing on the behavior of FeTaN films

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Abstract
A study of the effect of field annealing on soft magnetism in FeTaN films is presented. Changes with temperature (Ta) for longitudinal field annealing (LFA) and with time (ta) for transverse field annealing (TFA) are described. For LFA of 60 min, film properties are essentially unchanged up to 300 °C. Higher Ta leads to grain growth and TaN precipitation, along with substantial reduction of the magnetization and poorer soft magnetism. Changes in stress and magnetostriction are also observed. LFA also leads to an increase of the structure constant S. Consequently, lower μi and higher Hc are reported; Hk is gradually reduced. TFA has been performed at 150 °C, as a function of ta. A drastic change in Hk is observed, decreasing with increasing ta, switching from positive to negative values after 60 min and finally stabilizing after 120 min. The sign change of Hk indicates a complete rotation (90°) of the easy axis (EA). μi is highly sensitive to the change in Hk and can be significantly increased by lowering Hk. It is concluded that TFA can be instrumental in improving the softness of FeTaN films, but such treatment can also lead to a rotation of the EA, raising some concerns about the thermal stability of such materials.