Magnetostriction constants of [110] oriented epitaxially grown FeTaN thin films

The magnetostriction constants, /spl lambda//sub 100/ and /spl lambda//sub 111/, of FeTaN (10 wt% Ta) were determined in [110] oriented epitaxial thin films (/spl sim/1500 W) deposited by dc magnetron sputtering onto Cu[001] buffer layers (/spl sim/2000 /spl Aring/) which were grown on Si[001] single crystal substrates. The orientation relationship of the films was FeTaN[110]/spl par/Cu[001]/spl par/Si[001] with FeTaN<111>/spl par/Cu<110>/spl par/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 /spl lambda//sub 100/, and /spl lambda//sub 111/. 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 /spl lambda//sub 100/ decreases and /spl lambda//sub 111/ increases as a function of lattice dilation which was taken to be proportional to the interstitial concentration. At larger normalized lattice dilation, /spl sim/2%, /spl lambda//sub 111/ changed sign from negative to positive. The calculated saturation magnetostriction, /spl lambda//sub s/, using these values of /spl lambda//sub 100/, and /spl lambda//sub 111/ agreed with published data on nanocrystalline samples of the same composition with no additional assumptions.