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Notes: As-deposited, magnetically soft nanocrystalline FeTaN films are successfully grown by dc-magnetron reactive sputtering. Growth conditions are instrumental in extending the solubility limit of Ta in the bcc FeTa alloy. Nitrogen incorporation in FeTa films is found to be much higher than in Fe films and can be explained in terms of thermochemistry using a large Ta-N interaction coefficient. The influence of different alloying elements is discussed theoretically, with regard to the metal-nitrogen affinity. A "typical columnar microstructure'' associated with the sputtering process is identified and its evolution versus the extent of nitrogenation is described in detail. Stress, magnetostriction, resistivity, and magnetic properties are respectively described as a function of both Ta and N contents of the films. The magnetic behavior of as-deposited nanocrystalline FeTaN is found to be very sensitive to both the dimension of the grains, their morphology and the nature of the grain boundary material which represents a non-negligible volume fraction in nanocrystalline films. It is proposed that the columnar structure plays the key role in promoting a large perpendicular anisotropy component (K⊥) and controls a "Stripe Domain''-like behavior observed at high N contents, which cannot be explained in terms of film stress in this material. The contribution of the magnetoelastic anisotropy is also described. In summary, by breaking the columnar structure, the incorporation of nitrogen first decreases K⊥ below the critical limit for formation of stripe domains. In these conditions, N acts as a "grain refiner'' and excellent soft magnetic behavior is reported and explained in terms of "vanishing magnetocrystalline anisotropy.'' The good thermal stability of such soft films is confirmed. By contrast, higher nitrogen incorporation increases K⊥ above the critical limit, leading to a stable stripe domain-like structure which does not allow for soft magnetic properties. This phenomenon has been found to be reversible at low temperature where a complete restoration of the soft magnetic behavior has been observed. This anomalous result is explained by the transformation of the grain boundary material into a "low Curie temperature phase'' for large N contents. © 1996 American Institute of Physics.

Notes: Domain structures in thin-film heads can be significantly influenced by magnetoelastic anisotropy. In this study we have undertaken systematic measurements of magnetostriction and stress in as-deposited and annealed states in FeN and FeTaN single-layer thin films with varying nitrogen contents. Magnetostriction was positive for FeN films, increased with increasing nitrogen content, and shifted toward negative values after annealing. Stress in as-deposited FeN films was tensile and decreased (became more compressive) with increasing nitrogen content. Annealing the FeN films resulted in significant stress relief. By contrast, magnetostriction was found to be negative for simple FeTa (zero nitrogen) and increased linearly with increasing nitrogen content to positive values. The magnetostriction in FeTaN did not change significantly after annealing at 200 and 250 °C. FeTaN film stresses were compressive in the as-deposited state and increased in magnitude (became more compressive) with increasing nitrogen content. After annealing these stresses were relieved slightly. Ta has been found to be very effective in enhancing the thermal stability of the FeN films. © 1996 American Institute of Physics.

Notes: 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. © 1997 American Institute of Physics.