Intergranular Interactions in Fe-Ti-N Thin Films

This paper investigates the nature of the intergranular (IG) interactions for the Fe-Ti-N thin films as a function of the nitrogen content (x_N). This was done through measurements of isothermal remanence magnetization (IRM) and direct current demagnetization (DCD) and a Stoner-Wohlfarth (S-W) based interaction model for this uniaxial anisotropy system. The data indicate that the IG interactions are strong and predominantly exchange dominated for nitrogen amounts in the 0 -4 at. % range, become predominantly magnetostatic for 4 -8 at. % nitrogen, and switch back to exchange dominated for higher levels. The change in the IG interactions from exchange dominated to magnetostatic dominated and back again can be qualitatively explained by a grain size effect. For low x_N exchange dominates because the grains are large and there are few pores and grain boundaries. As x_N increases, the grain size decreases, there are more pores and grain boundaries, and the magnetostatic interactions become larger. Finally, as the grain size falls below the exchange length, the intergranular exchange coupling again dominates.