In future high bit density for perpendicular recording, the conventional single pole head will not be able to record to the medium because the track should become narrow and coercivity of medium should become high. A 2 steps type of single pole head whose main pole has two tips is proposed. The field generated from the 2nd tip adds the recording field beneath the 1st tip. With the soft backlayer of medium, the superposed net field strength can be beyond the saturation flux density of used head material itself. The head has a potential to realize 1 Tbits/in^2 recording proposed by IBM.
We demonstrated the measurement of the high frequency(HF)magnetic field of a write head with the phase detection magnetic force microscope. An amplitude-modulated current was applied to the head coil to detect the force gradient induced by the HF magnetic field. Spatial resolution of this method(AC-phase detection) was higher than that of the deflection detection method previously proposed(AC-deflection detection). By the phase detection method, dynamic HF magnetic fields and the magnetic field leakage were clearly imaged. The frequency dependence of the write head dynamics up to 350MHz was also investigated. Not only magnitude but also contrast(distribution)of the HF magnetic field that was caused by the eddy current was observed.
Effects of sputtering condition, underlayer and intermediate layer on magnetic properties have been studied in the Co-Cr-Pt film with high coercivity(Hc_⊥), large squareness(SQ_⊥)and large nucleation field(H_N). Hc_⊥ as high as 5000 Oe is obtained at low substrate heating temperature, by low power sputtering. An ultra thin Cr intermediate layer is effective in reducing the Co-Cr-Pt film thickness with maintaining high Hc_⊥.
Reduction of initial film-growth layer of CoCrPt based perpendicular recording media was investigated using TiCr, CoCr and Ru seed layers. The initial layer has small perpendicular magnetic anisotropy K_u, and the thickness of the initial layer was about 10〜15 nm with TiCr seed layer, and 1-6nm with CoCr or Ru Seed layers. X-ray diffraction patterns and TEM images indicated that the initial layer contains fcc-like structure. Moreover, a lot of stacking faults exist in the CoCrPt based perpendicular films even with CoCr or Ru seed layers. The improvement of epitaxial film growth by using CoCr or Ru seed layers is very effective to reduce the thickness of the initial layer, while is found to prevent the segregation of Cr from Co, resulting in larger intergranular exchange coupling.
Double layered Co-Cr-Pt-Nb film with high Pt content was investigated for obtaining a large perpendicular magnetic anisotropy. This film suppresses the reduction in H_c⊥ at high temperature atmosphere. A Pt(Pd)(stacked)intermediate layer enlarged perpendicular coedrcivity and squareness. It was found that an initial growing layer of the storage layer was reduced by the Pt/Ti stacked intermediate layer. Auger electron spectroscopy revealed that there was almost no oxygen at the initial stage of the storage layer growth. The Pt(Pd)layer can control the grain size of the storage layer to be small and uniform and improve magnetic characteristics of top layer.
Soft magnetic ferrite thin disk cores were prepared by Spark-Plasma-Sintering(SPS)method, using Mn-Zn or Ni-Zn-Cu ferrite powder as a starting material. In the SPS method, sintering is performed under uni-axial press with the assist of micro plama generated between powder materials. In the conventional method, it is necessary to set the temperature rising rate considerably slow because of indirect heating from the outside of a mold. However, it was proven that SPS method could sinter the ferrite in the short time than conventional method. Using spray-dried Ni-Zn-Cu ferrite powder with high-density, fine grain size and excellent soft magnetic properties were obtained.
Higher resolution mastering source than conventional laser is required to realize higherlensity next generation optical disk. An EBR(Electron Beam Recorder)was developed and satisfactory performance was observed on CD size 25GB capacity disk with it both on 2P disk and on injection molded disk. A possibility of CD size disk with more than 200GB capacity is shown under a certain EBR condition.
Scanning Nonlinear Dielectric Microscopy(SNDM)is the first successful purely electrical method for observing ferroelectric domains. Now its resolution has become to the sub-nanometer order. In this paper fundamental study on applying SNDM system to the ferroelectric reading and writing sistem is performed. At first, to check the performance of the SNDM system as a ferroelectric recording system, we conduct a fundamental study on the writing of domain inversion dot in PZT thin film and succeed have a very small domain dots with the size of 25nm. Next, we form small inverted domain dots in stoichiometric LiTaO_3 single crystal for the purpose of a basic investigation of domain dynamics in a very small area. The relationship between the voltage for domain reversal and the inverted area and the relationship between the inverted domain area and the voltage application time are obtained.