Orientation Effects of Barium Ferrite Media

Abstract

Abstract---A simple method for estimating the remanent magnetization vector angle (e) is introduced. By using this method, the orientation effects of Ba-ferrite FDs on the effective vector angle for the remanent magnetization and on recording characteristics were investigated. The resul ts show that the angle e depends on perpendicular squareness ratio (S~) and is independent from Hc. Also, the larger the S~ becomes, the higher the D50 becomes. The results also show that the higher the recording density becomes, the more perpendicularly the remanent magnetization vector becomes for the Ba-ferrite FD with a relatively low squareness ratio. INTRODUCTI ONBa-ferrite particulate media have been developed and utilized as high density recording media. Figure 1 shows typical density response curve for a commercialized Ba-ferrite FD (2ED type), compared with that for a conventional Co-y -Fe203 FD (2HD type). This figure shows that the Ba-ferrite FD provides much higher short wavelength output than the Co-y -Fe203 FD. However, Hc and Ms values for those two FDs are almost the same: Le., Hc = 750 Oe, Ms = 120 emu/cc for the Ba-ferrite FD and Hc = 730 Oe, Ms = 105 emu/cc for the Co-y -Fe203 FD. Moreover, the Co-y -Fe203 FD has less coating thickness than the Ba-ferrite FD: Le., 0.9p.m and 2.5p.m, respectively. Therefore, there seems to be no reason tha t the Ba-ferrite FD provides superior response at short wavelengths, as long as conventional longitudinal recording theory is applied. The main reason why the Baferrite media possess such fine short wavelength recording characteristics is believed to be owing to the fact that the remanent magnetization for Ba-ferrite FD comprises a rather large perpendicular component, even if the orientation of the Ba-ferrite media is not so high [11 [21. The purpose of this paper is as follows:(1) To estimate effective vector angle for the remanent magnetization in the Ba-ferrite media.(2) To investigate the effects dicular orientation on short characteristics.of perpenwavelength