Structure and magnetic properties of Fe-Cr-N ternary films prepared by DC magnetron facing-target sputtering have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM) and Mössbauer effect. These films exhibit perpendicular magnetic anisotropy. We found that N2-to-Ar flow ratio, Fe-Cr target area ratio and substrate temperature during film preparation are the factors influencing the anisotropy. Adjusting the chemical composition and deposition parameters, we obtained saturation magnetization of 300-400 emu/cm3 and perpendicular coercivity of 800-1100 Oe. XRD measurements show that the films generally consist of the α-Fe(Cr) and γ′-(Fe,Cr)4Nx(x < 1) phases, and that the enhancement of perpendicular anisotropy is always accompanied by a decrease in the grain size of α-Fe(Cr) phase and growth of the γ′-(Fe,Cr)4Nx phase with a pronounced (2 0 0) texture. The Mössbauer spectra show that the γ′-(Fe, Cr)4Nx phase is nonmagnetic at room temperature. Using the SEM and TEM, we found that the nonmagnetic γ′-(Fe,Cr)4Nx phase displays columnar growth and that the small ferromagnetic α-Fe(Cr) grains of about 2-20 nm in diameter are located at grain boundaries of γ′-(Fe,Cr)4Nx grains. Shape anisotropy seems to play an important part in the perpendicular magnetic anisotropy in these Fe-Cr-N films.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics