Magnetostriction constants of (110) oriented epitaxially grown FeTaN thin films

The magnetostriction constants, λ₁₀₀ and λ₁₁₁, of FeTaN (10 wt% Ta) were determined in (110) oriented epitaxial thin films (~1500 W) deposited by dc magnetron sputtering onto Cu(001) buffer layers (~2000 Å) which were grown on Si(001) single crystal substrates. The orientation relationship of the films was FeTaN(110)||Cu(001)||Si(001) with FeTaN<111>||Cu<110>||Si<100>, which was satisfied by four different, equally probable in-plane orientations of the crystallites. The magnetostriction measurement was carried out on a cantilever beam measurement system calibrated with (110) oriented epitaxial Fe films with the same morphology as the unknown films assuming the bulk values of λ₁₀₀, and λ₁₁₁ . The magnetostriction of FeTaN films was measured as a function of angle in the sample plane and fitted with the calculated average of the four orientations. In conflict with theoretical predictions, it was found that λ₁₀₀ decreases and λ₁₁₁ increases as a function of lattice dilation which was taken to be proportional to the interstitial concentration. At larger normalized lattice dilation, ~2%, λ₁₁₁ changed sign from negative to positive. The calculated saturation magnetostriction, λ_s , using these values of λ₁₀₀, and λ₁₁₁ agreed with published data on nanocrystalline samples of the same composition with no additional assumptions