FORMATION OF HEXAGONAL, PLATE-LIKE BA-FERRITE PARTICLES WITH LOW-TEMPERATURE DEPENDENCE OF COERCIVITY

Ba ferrite (Ba-Fe) has been prepared with a temperature coefficient of coercivity (d H(c)/dT) of 0 approximately -1 Oe/degrees-C, in the temperature range 0-80-degrees-C and coercivity range 500-1500 Oe. Superfine and platelike Ba-Fe particles containing Ti (IV), Ni (II) and Zn (II) were prepared by a wet method to examine their properties, using X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating-sample magnetometry (VSM). A magnetically oriented sheet was prepared in order to examine SFD (SFD(r)), SQ, S* (S(r)*) and the easy magnetization axis. It was found that Ni-Ti-Zn substituted Ba-Fe retains the characteristics of Co-Ti-substituted Ba-Fe. An environmental aging test of the particles also showed evidence of excellent stability. We conclude that Ni-Ti-Zn substituted Ba-Fe is suitable not only for existing magnetic recording media but also for future applications.