T. Kusuda
Hiroshima University
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Featured researches published by T. Kusuda.
Journal of Applied Physics | 1981
Shin‐ichi Yasugi; S. Honda; M. Ohkoshi; T. Kusuda
Structures and compositions of sputtered GdCo films were carefully investigated using a carbon‐replica technique and Auger electron spectroscopy. In zero‐bias sputtered films, the columns are clearly observed to develop perpendicular to the substrate, and they become fine with increasing Gd content up to near the compensation composition from pure Co film. For negative‐bias sputtered GdCo films having near compensation composition, the film structures become fine with increasing negative bias up to 200 V. The observed increment of perpendicular anisotropy in this negative bias region was explained by the structural change of the columns (shape anisotropy and stress induced anisotropy). Above 200 V negative bias, the column structures are damaged partially by Ar‐ion‐bombardment, and then the anisotropy decreases due to the damage of columns. The change in the saturation magnetization due to negative bias was interpreted by the change in the film composition; Gd‐content and oxygen.
IEEE Transactions on Magnetics | 1985
M. Ohkoshi; M. Harada; T. Tokunaga; S. Honda; T. Kusuda
Effects of Ar pressure and negative substrate bias voltage on magnetic properties and micro-structure in amorphous TbCo sputtered films are investigated. Magnetic properties, especially perpendicular anisotropy, depend strongly on Ar pressure and substrate bias. A perpendicular anisotropy of the order of 106erg/cm3with a rectangular hysteresis loop is induced in the films deposited at 10 mTorr of Ar pressure without bias or in the films deposited with 100-150 V negative bias. In these films, the ordered fiber structure developed perpendicular to the film plane is observed, which is due to the moderate bombardment of energetic species. The large perpendicular anisotropy is associated with the ordered fiber structure.
ieee international magnetics conference | 1990
S. Honda; H. Tanimoto; T. Kusuda
The film structures and magnetic properties of Co/Pt multilayers prepared by magnetron sputtering are examined. The multilayer consists of columns of 50 approximately 100 AA diameter grown vertically to the film plane, and the coercive field becomes smaller with decreasing thickness ratio of Co to Pt layers and with decreasing also total film thickness. The coercivity, however, can be enlarged up to about 3 kOe by a Pt underlayer even in ultrathin Co/Pt films. The magnetization process and the behaviour of the magnetic domains are explained by the mixing mode of the wall motion and the moment rotation. >
Japanese Journal of Applied Physics | 1988
S. Honda; Toshiaki Yamakawa; Kenichi Takahashi; T. Kusuda
Stripe domain patterns were clearly observed in CoCr-sputtered films using the Bitter method. These patterns suggested that wall motion dominates the flux reversal for films having a low coercive field; however, both the wall motion and rotational modes take place in a flux reversal for films having a high coercive field. Therefore, the hysteresis loops and angular dependence of the coercive field for CoCr sputtered films were calculated based on the assumption of a simultaneous occurrence of the rotational and wall motion modes. Good agreements were obtained between the experimental and calculated results.
ieee international magnetics conference | 1989
S. Honda; S. Nishimura; T. Kusuda
The periodicity dependence of the crystallographic structure and saturation magnetization are examined for Dy-Fe and Tb-Fe multilayered films prepared by an evaporation technique. The magnetization of Dy-Fe films changes nonlinearly with the periodic length Lambda , while that of Tb-Fe decreases linearly with shortening of Lambda . The perpendicular anisotropy K/sub u/ increases reciprocally with Lambda owing to the surface anisotropy K/sub s/. The value of K/sub s/ for Tb-Fe is about 1.7 times higher than for Dy-Fe at room temperature. The value of Dy-Fe increases with decreasing temperature; also, K/sub s/ at 80 K is about 1.5 times its value at room temperature. >
IEEE Transactions on Magnetics | 1986
S. Honda; M. Ohkoshi; T. Kusuda
Compositionally and morphologically modulated TbCo films were prepared on glass substrates by changing negative bias voltage between 0 and 100V or 150V alternately using RF sputtering method. The films having 12 - 36 layers (layer thickness of 250 - 80 A) show high magnetic coercivity and high resistivity to oxidation. In these films, small stable bits can be written magneto-optically.
Journal of Magnetism and Magnetic Materials | 1983
M. Ohkoshi; H. Toba; S. Honda; T. Kusuda
Abstract The magnetization curling in the CoCr film is found by a high resolution Lorentz microscopy technique. Several grains assemble to form a column, and it is observed to behave as a magnetic cluster. The magnetization reversal process is performed by the rotational switching in the magnetostatically coupled individual cluster.
Journal of Applied Physics | 1982
T. Kusuda; S. Honda; M. Ohkoshi
Some important information about the structural change of GdCo sputtered film with substrate bias is obtained by using the replica technique. It is found that the increase in perpendicular magnetic anisotropy for increasing substrate bias is related directly with the ultrafine microstructure of the GdCo film. The relative substrate potential with respect to the Ar plasma depends either on Ar pressure during sputtering or on the external substrate bias. When this relative substrate potential becomes negative by a certain amount, sputtering of surface oxygen and resputtering of Gd in the growing film will be initiated, and consequently the structure of sputter‐deposited film will change. The origin of microscopic perpendicular magnetic anistropy with or without substrate bias is described by a model proposed earlier for Permalloy films. The perpendicular magnetic anisotropy based on this microscopic shape anisotropy model is Ku = 2πMs2(δ/a), where δ is the thickness of the nonmagnetic boundary and ’’a’’ is ...
IEEE Transactions on Magnetics | 1984
M. Ohkoshi; K. Tamari; S. Honda; T. Kusuda
The perpendicular magnetization state is realized in Co-CoO film prepared by reactive RF sputtering in argon-oxygen mixture. With increasing the oxygen partial pressure, saturation magnetization of the deposited film decreases monotonically due to the formation of CoO. The film is composed of fine particles of hcp Co and fcc CoO. The perpendicular magnetic anisotropy energy and the coercivity reach to 3 × 106erg/cm3and 2 kOe, respectively. Above a critical partial pressure of oxygen, the deposited film has no spontaneous magnetization with a Co 3 O 4 single phase. The observed columnar structure in the Co-CoO film becomes fine with increasing the oxygen partial pressure. The exchange anisotropy is found in the Co-CoO film. The perpendicular magnetic anisotropy in the film is likely to be originated from an anisotropic assembly of ferromagnetic Co particles and antiferromagnetic CoO particles.
IEEE Transactions on Magnetics | 1984
S. Honda; N. Yamashita; M. Ohkoshi; T. Kusuda
Annealing effects on magnetic properties of CoCr sputtered films were investigated. The anneal in air near 400°C causes the considerable increase of the saturation magnetization M s , the perpendicular coercivity H c ( \perp ) and the perpendicular anisotropy K u . These increments were interpreted by the formation of antiferromagnetic Cr 2 O 3 surrounding column boundaries, which was supported by the depth profiles of AES and the spectrum of ESCA. Furthermore, the variations in magnetic properties are fairly suppressed by coating the film surface with a SiO 2 or AlN layer.