This paper report the simulated results of modified anhysteretic remanence(MAR)process in rotating vectorial AC bias field by a two-axis VSM. Using a macroscopically isotropic small disk sample made of VHS tape couons, the effects of perpendicular component and rotation of the head field on the MAR have been clarified, comparing with the conventional scalar VSM simulation. It was found that rotating vectorial AC bias head field needs about 1.2 times smaller magnitude than scalar AC bias head field to acquire the same level of MAR, and that MAR in vectorial field has large perpendicular component, suggesting significant effect on MAR of the sample orientation and the direction of the measurement with respect to the sample shape.

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Amorphous Co-Zr(-Ta) films which have larger saturation magnetization than Ni-Fe ones were deposited by using the facing targets sputtering (FTS) apparatus for the applications as backlayer in perpendicular magnetic recording media. Co-Zr films revealed good soft magnetism when films were prepared at low Kr gas pressure and at low substrate temperature. Ta was added to Co-Zr to enhance fine granulation and to decrease the magnetostriction constant. The minimum H_c of 0.75 Oe and the maximum μ_r of 580 were obtained for the films with composition of Co_85.2Zr_3.6Ta_11.2

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In a double layered CoCrTa film separated by a thin flash Cr interlayer, coercivity and coercivity squareness drastically change with increasing the Cr interlayer thickness. There was some coercivity increase in double layered films compared to single layer when the flash Cr interlayer thickness were around 8 to 10A and coercivity decreased with further increase of the Cr interlayer thickness up to 50A. A micromagnetic simulationt technique was employed to understand the coerdvity changes as a function of the interlayer thickness. The simulation results showed fluctuation of coercivity at a thin interlayer thickness range and coercivity becomes a constant value with further increase of the interlayer thickness. These will be discussed.

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Magnetic properties of CoCrTa/Cr thin films deposited with DC bias voltage ranging from 0 to -500V were studied. Three different kinds of biasing schemes were used ; Cr layer bias, Co layer bias, Cr and Co layers bias. In all cases, coercivity increased to a maximum value at -300V bias and decreased with further increasing bias voltage. When Cr layers were biased the cause of coercivity increase could not be interpreted by accounting the intensity change of Co (1011), (1010) and (1120) planes only and it is concluded contribution of Cr morphology change on CoCrTa grain separation must be substantial. The increase of coercivity in the CoCrTa biased specimens is understood as enhanced segregation of Cr with the increasing bias voltage. These and other contributions on the coercivity increment will be discussed in detail.

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The effect of additional element Cu and Ni into Cr underlayer on a CoCrTa/Cr sputterd thin films was investigated. Cu ad Ni contents effects on the magnetic and structural properties of CoCrTa/Cr was also investigated. The addition of Ni into Cr underlayer made a XRD peak shift to higher 20 indicating the decrease of interplanar distance. It has been shown that the intensity and d-value of Cr(110) peak revealed the different tendency for the increase of the content of Cu and Ni. The increase in coercivity may be resulted from the change of Cr underlayer microstructure, leading to the change of CoCrTa magnetic layer microstructure.

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Elemental segregations of CoCrTa thin films for longitudinal and perpendicular media are investigated using high spacial resolution transmission electron microscopes equipped with compositional analysis facilities. Strong Cr segregations exceeding 25 at% are observed at grain boundaries for both types of CoCrTa films prepared at elevated substrate temperatures. The thickness of the Cr-enriched layer is estimated to be 1.5 -2nm. The Cr segregation at bi-crystalline boundary observed for a longitudinal CoCrTa film is lower than that observed at normal grain boundary. The Cr concentraion inside the magnetic crystal grain is ranging between 6 and 12 at.% which is lower than the average Cr composition. The strong Cr segregations are correlated with the high coercivity of CoCrTa perpendicular medium.

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A deposition of a perpendicular double layer medium with a sputtering apparatus equipped an aluminum chamber is discussed. High speed pumping and clean atmosphere of little H_2O is obtained associated with a liquid nitrogen shroud. Relatively low coercivity and smooth film surface are obtained for an underlayer of the medium. Mainly as this morphological result high output at high linear density is attained.

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The effect of the under layer on surface smoothness of a simultaneously double coated MP tape was investigated. A smooth surface of the under layer could be obtained by highly dispersing particles in the under layer. The pore volume of the under layer decreases with an increase in the degree of dispersion of the particles. The double-layer coatings showed approximately the same storage modulus, E' values over 100℃ independent of binder resins used, which suggests that they indicate the same viscoelastic behavior at calendering temperature. The surface of the double coated tape with the under layer having a good dispersion of particles was smoother than that of the single magnetic layer. The improvement of electromagnetic characteristics was due to both the reduction of surface roughness and the thinner thickness of the magnetic layer.

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An 8mm wide Co-Cr-Ta/Ni-Fe perpendicular magnetic recording tape has been developd for digital vdeo recording. Digital video recording at about 4 times the area density of a D-3 VTR was achieved using the digital signal processing circuit of the D-3 VTR and an improved tape transport system based on the 8mm VTR. An SN ratio of 34.7dBp-p/rms was obtained using a ring head with a 10μm track width when the 27.7MHz rectangular signal, equivalent to the shortest recording wavelength, was recorded and reproduced.

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Co/Pd multilayers have been studied for their application as perpendicular magnetic recording media. Cover glasses were used for substrates and Co/Pd multilayers were prepared by means of a vacuum evaporation deposition method. A perpendicular magnetic anisotropy was obtained when the Co layer thickness was about 0.4 nm. In order to prepare Co/Pd multilayers with high coerecivity, various kinds of buffer layers have been investigated. A perpendicular coercivity as high as 2400 Oe was obtained with a Ti(100nm/Pd(25nm) buffer layer prepared at a substrate temperature of 200℃. The adhesion strength between the multilayer films and the glass substrates has been significantly improved with the buffer layer. Finally, a high recording performance was confirmed for the Co/Pd multilayer disk medium by a read/write test using a ring head.

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Co/Cr and Co/Mo multilayer thin films deposited by the e-beam evaporating method have an alternating layered structure. The structure of film with thicker Co layers than Cr and Mo layers are found to be a hcp structure with the c-axis normal to the film plane. The direction of the film plane is the easy magnetization one. There is a no significant difference in shape of hysteresis loops between Co/Cr and Co/Mo multilayer films. Mo layer is more effective than Cr for preparing Co layer with c-axis normal to the film plane.

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Co/Pd and Co/Pt multilayers wilt Pd or Pt base layers were prepared by rf magnetron sputtering and the effects of sputtering pressure during the formation of base layers on the magneto-optical properties of multilayers were investigated. It has been found that coercivity of Co/Pd multilayers was strongly dependent on the sputtering pressure of base layer and could be enhanced to a great extent without noticeable change of Kerr rotation angle by increasing the sputtering pressure of base layer. On the contrary, it turned out that the deposition pressure of base layer gave a little effect on the coercivity of Co/Pt multilayers. For the both multilayers, rectangularity of M-H curves became bad as the deposition pressure of base layer increased.

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