Epitaxial Ni3FeN thin films: A candidate for spintronic devices and magnetic sensors

Abstract

A new type of epitaxial ferromagnetic nitride (Ni3 Fe N = permalloy nitride = “PyN”) compound films were grown on Al2O3(112¯0) substrates using reactive triode magnetron sputtering. The results of electron back-scattering diffraction and x-ray diffraction techniques indicate a high quality epitaxial crystalline structure with growth normal of (100). Magnetization measurements of epitaxial PyN films revealed several unique results. (1) A textbook square hysteresis loop that suggest existence of single magnetic domain in these films. (2) A coercive field is tunable from a few mOe up to a few Oe by changing the film thickness. (3) A magnetization that switches (rotate) over a very small field range of δHC ≤ 0.05 Oe, independent of the film thickness. This small δH indicates a very large resistive sensitivity (δR/δH) of the epitaxial PyN. (4) The epitaxial PyN thermal cycling through several cycles between “2 and 800 K” (−271 °C to +527 °C) shows much less degradation only about 2–5% compared to 40% degradation of a simple Py film. Four-probe transport measurements give an anisotropic magnetoresistance of ≈6%, sufficiently higher than other known ferromagnetic materials. These interesting properties are ideal for a variety of spintronic devices and magnetic sensors.