Magnetic ordering in amorphous Bi2O3-ZnO-Fe2O3 films sputtered at high temperatures

The onset of a long-range magnetic order is reported in amorphous Bi2O3-ZnO-Fe2O3 films sputtered at high substrate temperatures. Samples of 0.1 Bi2O3-0.4 ZnO-0.5 Fe2O3 were deposited in a mixed oxygen-argon atmosphere at substrate temperatures Ts=450–875 K. Films are found to be x-ray amorphous for Ts≤675 K. For higher Ts values, nonmagnetic crystalline phases are precipitated in the sample. The samples are paramagnetic at room temperature for substrate temperatures below 475 K. A spontaneous magnetic moment is observed in films deposited at higher Ts. The saturation-induction 4πM at 77 K is in the range 800–3600 G and 4πM increases with increase in Ts. The Curie temperature is found to decrease with Ts. A uniaxial anisotropy character in the films is evident from ferromagnetic resonance studies. Thus, data on structural and magnetic parameters indicate the possible presence of ordered clusters in films sputtered at high temperatures. The presence of ordered clusters need to be independently confirmed with techniques such as transmission electron microscopy.