A barium hexaferrite (BaFe12O19, magnetoplumbite structure, BaM) multilayered film, with a total thickness of 0.63 μm, was deposited on a Si substrate by stacking several 0.09 μm layers using a rf sputtering technique. Each 0.09 μm layer was ex situ annealed at 800 °C for 10 min prior to deposition of the succeeding layer. A vibrating sample/torque magnetometer was employed to characterize the magnetic properties of both the BaM multilayered and a single layered film of the same thickness. The 0.63 μm thick BaM multilayered and single layered films show a squareness (SQ=Mr/Ms at 7 kOe) of 0.81 and 0.62, respectively. An anisotropy field (HA) was found to be 17 kOe for the BaM multilayered film and 14.5 kOe for the single layered film. A stacking of BaM layers, with ex situ annealing between each layer, improves the c-axis orientation and anisotropy field as compared to a single layered film with the same thickness. This is attributed to limiting the number of nucleation sites for randomly oriented BaM crystallites existing in films thicker than 0.1 μm.

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Thickness, resistivity, and the Gilbert damping constant are estimated using Maxwell and Landau-Lifshitz-Gilbert (LLG) equations to meet operating parameters of ferromagnetic thin film inductors in the gigahertz frequency range. The following properties of soft magnetic film are calculated to satisfy a quality factor of 10 at 3 GHz: 4 = 21 3 kG; = 215 Oe; and = 100. The complex permeability was not influenced by film thickness up to 100 nm. Operation frequency increases with the increase of electrical resistivity and decrease of film thickness. The Gilbert damping constant is found to have a significant effect on the operation frequency. The quality factor can be retained up to 3 GHz for 100-nm-thick film with a damping constant of 0.015 when resistivity is greater than 50 cm. Index Terms-Ferromagnetic resonance, LLG equations, soft magnetic materials, thin film inductor.

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