INFLUENCE OF COMPOSITION AND OXYGEN PARTIAL-PRESSURE IN SINTERING ATMOSPHERE ON MICROSTRUCTURE AND MAGNETIC-PROPERTIES OF NI-ZN FERRITE FORTHIN-FILM MAGNETIC RECORDING-HEADS

Ni-Zn ferrite is a promising material as the substrate for thin film m agnetic recording heads. The influence of specimen composition and par tial oxygen pressure (P-O2) in sintering atmosphere (N-2+O-2) on the m icrostructure and magnetic properties of Ni-Zn ferrite has been invest igated by SEM and XPS. The results obtained are summarized as follows. (1) ZnO precipitates were observed at the grain boundaries, especiall y at the triple points of the Ni-Zn ferrite specimen sintered al 1453 K for 10.8 ks under 20% P-O2. Such precipitates, however, were not det ected in the specimen sintered in the atmosphere whose P-O2 was 25%. ( 2) Although the permeability (mu) and the resistivity (rho) of the Ni- Zn specimens sintered at 1453 K for 10.8 ks under 10 to 100% P-O2 incr eased with increasing P-O2, both the loss coefficient (Q) and the rela tive loss coefficient (tan delta/mu) showed an optimum value under 20% , P-O2. (3) The 0.3 mol% increment of ZnO and the 0.3 mol% decrement o f NiO than the conventional composition (Fe2O3: 49.7 mol%, ZnO: 32.6 m ol%, NiO: 17.7 mol%) prevented ZnO precipitation on the Ni-Zn ferrite specimen sintered at 1453 K for 10.8 ks in air. (4) The HIP'ed specime n after sintered at 1423 K, 30 K lower than the conventional sintering temperature of 1453 K, in air showed neither ZnO precipitation nor po res.