Surface morphology, structure, magnetic and electrical transport properties of reactive sputtered polycrystalline Ti1−xFexN films

Polycrystalline Ti1−xFexN films with different Fe atomic fractions (x) were fabricated by reactive facing-target sputtering. The lattice orientation changes from (2 0 0) to (1 1 1) with the increase of x, which makes the surface morphology evolve from spherical, triangular-pyramid-like islands to random-leafs-like ones. The films are ferromagnetic with a Curie temperature of higher than 305 K, and the saturation magnetization (Ms) is very small. Obvious asymmetric M–H curves are observed at low temperatures, and the shift of M–H curves decreases with the increasing temperature because of the relaxation of the pinned moments at low temperatures. All of the samples show semiconducting-like behavior with a mechanism of variable-range hopping at low-temperature range. Magnetoresistance (MR) is very small. The small Ms and MR can be explained by the facts that the interaction between Fe3+–N3−–Fe3+ is antiferromagnetic superexchange coupling, and no double exchange exists in Fe3+–N3−–Ti3+, which is different from that in the Cr-doped TiN films.