Theoretical study of magnetostriction in FeTaN thin films

Single layer films of FeTaN have been deposited by dc magnetron sputtering, and the relationships between the magnetostriction and film composition have been studied. A linear increase in magnetostriction with nitrogen content has been explained by the dependence of λ100 on nitrogen concentration. The form of this dependence has been derived based on a theory developed by De Vries for describing the magnetic after effect in iron films with interstitial nitrogen. At room temperature, the best fit for the experimental magnetostriction data was found for an interstitial interaction constant of D=4.18×106 J/m3. The total magnetic anisotropy energy per grain, U110, has also been calculated as a function of the strain for FeN films with a (110) orientation under a tetragonal deformation. This calculation used the results derived for the dependence of the magnetostriction constant, λ100, on nitrogen concentration. The calculated U110 value shows a minimum at a lattice strain value of ε11=0.0029, in close agreement with a maximum in permeability at Δd110/d110=0.0028 previously reported for FeN films.