Shigekazu Otomo

Magnetic properties of multilayered Fe-C film formed by dual ion beam sputtering

The magnetic properties of both single-layered and multilayered Fe-C films formed by dual ion beam sputtering are studied. When the C concentration in Fe-C films increases, the relative permeability of the film increases and the coercivity decreases. The relative permeability of single-layered Fe-9at%C film with a magnetostriction constant nearly zero, is 550 at 5 MHz, even though that of pure Fe is only 150. When a multilayered film is made by alternating 5nm thick permalloy intermediate layers with 95nm thick Fe-C films, the soft magnetic properties of the resulting film show tremendous improvement. Multilayered Fe-9at%C film shows a relative permeability of 1400 and a coercivity of 200A/m. Compressive stress up to -2 × 109N/m2exists in this film. This stress can be relieved by heat treating the film in Ar, which improves the soft magnetic properties. The Fe-9at%C/permalloy multi-layered film annealed for 1 hour at 400°C shows a saturation magnetic flux density of 2.1T, a relative permeability of 3000 and a coercivity of 80 A/m.

Dynamic micromagnetic field measurement by stroboscopic electron beam tomography

A stroboscopic electron beam tomography system for measuring the dynamic micromagnetic field of recording heads is presented. A pulsed electron beam, which is synchronized with the recording head driver, is scanned along the recording head surface from all directions. Integration of the magnetic field intensity along the beam path is calculated from the electron beam deflection angle. Intensity distributions of the dynamic magnetic field are calculated using a tomographic reconstruction algorithm. To obtain enough current even in pulsed electron beam operation, a high-brightness Ti/W thermal field emitter is used. This system was successfully applied in measuring the field distributions of a thin-film recording head, with 0.1 mu m spatial resolution and 1 ns time resolution at an operation frequency of 30 MHz. >

Magnetic properties, aging effects and application potential for magnetic heads of Co‐Fe‐Si‐B amorphous alloys

Zero magnetostrictive alloys (Co0.94Fe0.06)‐Si‐B about 5mm wide and ∼25 μm thick were prepared by the single roller type quenching method. By choosing proper compositions and by annealing at temperatures higher than the Curie temperature, the alloys with saturation magnetic flux density of 0.95 T in which permeabilities are as high as 500 at 5 MHz, were obtained. The permeabilities at frequenceis below about 100 kHz decrease drastically even by aging at temperatures as low as 100°C. At high frequencies above about 500 kHz, no significant changes occur in the permeabilities by similar aging. Therefore, the alloys are suitable for high frequency applications. Recording and reproducing characteristics of a video head made of the amorphous alloy were measured at frequencies from 1 to 6 MHz, using Co‐γ‐Fe2O3 magnetic tapes. The output signals for the head are higher than those for both Mn‐Zn ferrite heads and Sendust alloy heads.

Magnetic properties and corrosion resistance of Fe-based sputtered films

The effects of elements added to Fe-based sputtered films are investigated to obtain magnetic thin films with a high-saturation magnetic flux density, Bs, a zero magnetostriction constant, λs, and high corrosion resistance. The Fe films, sputtered at argon pressures below 10 mTorr, have the same Bs as bulk samples. They also show high corrosion resistance. Although the λs of Fe film has a large absolute value, zero-magnetostriction films are obtained by the addition of 1 to 5at% Si, Cr, Mo, Ni, Ru or Rh. Samples containing Ni or Rh maintain a high Bs, of about 21 kG. However, the addition of Si, Mo and Cr cause a marked deterioration in corrosion resistance, while samples containing Ni, Ru or Rh show high corrosion resistance. The anodic polarization curves show that films with high corrosion resistance have high pitting potentials. This result suggests that the pitting is dominant in the corrosion of Fe-based films.

A study on the field distribution of thin-film heads

The field distribution of a thin-film inductive head and its relationship to pole configurations are examined. Three components of the field distribution at high frequencies are measured using a newly developed electron beam tomography method. Focused ion beam etching is used for the processing of the pole configuration. A comparison between the measured field distribution and the results of three-dimensional computer simulation shows that a sharp field distribution suitable for high-density recording is produced to promote magnetization at the tip region. Furthermore, the optimum design of the pole configuration clarifies the feasibility of 1- mu m track recording. >

Magnetic properties and thermal stability of Co-TM-Zr (TM=Nb, Ta, Mo, W, and Ni) amorphous sputtered films for magnetic heads

The magnetic properties and thermal stability Co-TM-Zr (TM=Nb, Ta, Mo, W, and Ni) amorphous films prepared by rf diode sputtering are investigated. Amorphous films with a homogeneous structure and coercive force Hc of less than 20 A m−1 are obtained at an argon gas pressure of 0.3–1 Pa. The formation range of the amorphous films is broad in the systems containing Ta and Nb, whereas it is limited to the composition range greater than 4–5 at % of Zr in the systems of Mo, W, and Ni. The magnetostriction λs depends on the concentration ratio of Zr and the TM. Films with zero λs are obtained at concentration ratios Czr/CTM ranging from 0.3 for Co-Nb-Zr films to 1.5–1.7 for Co-W-Zr films. The crystallization temperature Tx is highest in Co-Ta-Zr films and lowest in Co-Mo-Zr films when λs is zero and both films have the same saturation magnetic flux density Bs. The anisotropy field Hk is highest in Co-Ni-Zr films and lowest in Co-Nb-Zr films. These results indicate that Co-Ta-Zr and Co-Nb-Zr amorphous films are suitable for use as magnetic head materials because of the Co-Ta-Zr films high Tx and Bs, and the Co-Nb-Zr films small λns and low HK

A cross-type amorphous video head

Abstract A cross-type video head composed of cross-shaped amorphous sputtered films and ferrite that can be used with high coercive tapes is described. A three-dimensional magnetic field calculation shows that the cross-type head has a strong recording field and high reproduction efficiency compared to a conventional metal-in-gap head (MIG) or a plate-type head. No large bumps in the output spectrum are observed during recording and reproduction under normal conditions with the cross-type head. The amorphous sputtered film deposited on the inclined plane of the ferrite substrate used for the cross-type head shows a homogeneous structure and high permeability similar to that of a film deposited on a horizontal plane. A cross-type head using a CoNZr amorphous film annealed in a magnetic field under optimum conditions shows excellent recording and reproduction characteristics when used with a high coercivity metal tape.