Thermal stability of FeTaN as a function of N and Ta content

FeTaN thin films promise to be a good candidate for inductive head pole materials. FeTaN thin films which are nanocrystalline and possess the required magnetic properties in the as-deposited state are advantageous because they do not require a high temperature processing anneal. However, FeTaN films must possess sufficient thermal stability in order to maintain their magnetic properties while being processed into inductive heads. In this study we have undertaken systematic microstructural and magnetic measurements on nanocrystalline, single-layer FeTaN thin films as a function of N and Ta content and annealing temperature. The annealing temperatures used are less than 300°C and are meant to simulate head processing conditions. The addition of Ta was found to enhance thermal stability. By stabilizing the microstructure, Ta also stabilizes magnetic properties such as coercivity and magnetostriction (structure determines properties). The optimum amount of Ta for thermal stability while maintaining good magnetic properties was 10 weight percent. In the highest N content Fe-10TaN thin films, soft magnetic properties were found to be controlled by the magnetic domain structures which are governed by magnetoelastic anisotropy. These films which exhibited a magnetoelastic anisotropy less than -2×10⁴ ergs/cm³ also exhibited stripe domains which resulted in relatively high coercivities