Formation of oriented nitrides by N+ ion implantation in iron single crystals

Iron single crystals were implanted with nitrogen at room temperature, with a fluence of 5×1017 cm−2 and 50 keV energy, to produce iron nitride phases and characterize the influence of the crystal orientation. The stability and evolution of the nitride phases and diffusion of implanted nitrogen were studied as a function of successive annealing treatments at 250 °C in vacuum. The composition, structure and magnetic properties were characterized using RBS/channeling, X-Ray Diffraction, Magnetic Force Microscopy, Magneto-optical Kerr Effect and Conversion Electron Mössbauer Spectroscopy. In the as-implanted state the formation of Fe2N phase was clearly identified in all single crystals. This phase is not stable at 250 °C and annealing at this temperature promotes the formation of ε-Fe3N, or γ′-Fe4N, depending on the orientation of the substrate. - Highlights: • Oriented magnetic iron nitrides were obtained by nitrogen implantation into iron single crystals. • The stable magnetic nitride phase at 250 °C depends on the orientation of the host single crystal, being γ'-Fe4N or ε-Fe3N. • The easy magnetization axis was found to lay in the (100) plane for cubic γ'-Fe4N and out of (100) plane for hexagonal ε-Fe3N