STRESS-INDUCED MAGNETIC-ANISOTROPY IN THICK ORIENTED NIZN-FERRITE FILMS ON (100)MGO SUBSTRATES

Thick films (10-12 mu m) of NiZn-ferrite (Ni0.6Zn0.4Fe2O4) were grown on single-crystal (100) magnesium oxide substrates using pulsed laser deposition (PLD). The morphology, phase, orientation, strain, and magn etic properties of the as-deposited films were investigated as a funct ion of substrate temperature (400-700 degrees C) and O-2 background pr essure (50-200 mTorr). Compositional analysis shows that the PLD NiZn- ferrite films are about 45% Zn deficient when grown using a standard p olycrystalline single phase Ni0.4Zn0.6Fe2O4 target regardless of subst rate temperature or O-2 pressure. However, Zn-rich targets were succes sfully used to compensate for the Zn deficiency in the NiZn-ferrite fi lms. PLD NiZn-ferrite films grown at 700 degrees C exhibit the highest degree of crystalline quality and nearly bulk saturation magnetizatio n values (i.e., 5000 G). At low O-2 pressures (<75 mTorr) the films, w hich were grown at 700 degrees C, are under a significant compressive stress. The stress decreases when the PLD NiZn-ferrite films are grown in higher O-2 pressures but the crystalline quality and surface morph ology deteriorate. The compressive stress produces a planar anisotropy field of about 1000-3500 Oe depending on the O-2 pressure, which is c onsistent with the stress results from x-ray diffraction measurements on the NiZn-ferrite films. It is hypothesized that the film stress is largely the result of oxygen loss from the films during deposition. (C ) 1997 American Institute of Physics.