The temperature dependence of magnetization has been determined for sputter-deposited Fe-Cr-N films with perpendicular magnetic anisotropy. Decomposition and phase transformation with heating have been determined by X-ray diffraction, differential scanning calorimetry, and thermomagnetometry. There are three magnetic transformation stages in the temperature-rising thermomagnetic curves. The first stage which occurs below 350 degrees C corresponds to the paramagnetic transition of the ferromagnetic alpha-Fe-Cr phase. The second stage (350-550 degrees C) is the decomposition of the alpha-Fe-Cr and nonmagnetic gamma'-(Fe,Cr)(4)N-x phases into the pure alpha-Fe and sigma-FeCr phases, leading to an increase of the magnetization and the disappearance of the perpendicular magnetic anisotropy. The final magnetic transformation stage is the paramagnetic transition (T-c=735 degrees C) of the pure alpha-Fe phase. Since there is no rapid magnetization change between liquid helium temperature and room temperature, the gamma'-(Fe,Cr)(4)N-x phase is nonmagnetic at low temperatures. (C) 1998 Elsevier Science S.A
