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N Hiratsuka, M. Nozawa, K. Kakizaki
1996 Volume 20 Issue 2 Pages
53-56
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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Cobalt ferrite films with perpendicular magnetic anisotropy were prepared by facing-targets sputtering, and their magnetic properties and structure were investigated. A film deposited at
Po2=0 mTorr and post-annealed at 300°C had
Hc⊥ = 1.5 kOe,
Hcr=3.5, and
Sq⊥=0.46. The film deposited at
Po2=0 mTorr and post-annealed at 300°C had outstanding squareness ratio (
Sq⊥) compared with that of a CoFe
2O
4 single-phase film. When the binding energies of the Co
2p and Fe
2p electrons of the film were measured by XPS, the film was found to be made up of a (CoFe
2O
4)-(Co-CoO) composite.
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K. Sato, S. Yamamoto, H. Kurisu, M. Matsuura
1996 Volume 20 Issue 2 Pages
57-60
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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Co-Cr single-layer perpendicular anisotropy films were prepared on polyimide films by sputtering using electron cyclotron resonance (ECR) microwave plasma. The dependence of the crystallographic and magnetic properties of the Co-Cr films on the Ar gas pressure,
PAr, and the target-to-substrate distance,
DT-S, was investigated. An 0.09,μm thick Co-Cr film with excellent
c-axis orientation—namely,
Δθ50 of 3.35°—, a high perpendicular magnetic anisotropy field of 4.5 kOe, and a high perpendicular coercivity
Hc⊥ of 1530 Oe was achieved at a relatively high
PAr of 8×10
-2 Pa and a large
DT-S of 230 mm. It may be surmised that ion bombardment with moderate energy in the
PAr and
DT-S conditions described above is suitable for the deposition of Co-Cr perpendicular anisotropy films.
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H. Momiji, K. Adachi, K. Akagi, M. Futamoto
1996 Volume 20 Issue 2 Pages
61-64
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The structures and magnetic properties of CoCrPt/Cr thin-film media prepared at low temperatures are studied with a view to using the media on pre-embossed plastic disk substrates. Increasing the underlayer thickness causes isolation of the magnetic grains, which are epitaxially grown on the Cr grains. This isolation increases both the coercivity and the fluctuation field, which is reported to be inversely related to the medium noise. Decreasing the magnetic layer thickness from 40 nm to l 0 nm also increases the fluctuation field without significantly decreasing the coercivity. A film with an isolation-enhanced structure and with a thin magnetic layer of 20 nm prepared on a glass substrate shows a signal-to-noise ratio of 30 dB in 50kFCI recording. A linear density resolution (
D50) of 72 kFCI is also observed.
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I. Kobayashi, K. Uchida, K. Ohashi, K. Yamaguchi, Y. Sano, T. Ishii
1996 Volume 20 Issue 2 Pages
65-68
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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Thin film texturing of magnetic recording media is necessary for good stiction characteristics. This paper investigates the effect of a thin film texture on the medium noise.Thin film textured samples, Tex E (
Ra=6.8 nm) and Tex J(
Ra= 16.1 nm), and a non-textured sample, non-Tex (
Ra= 1.1nm), were fabricated by sputtering. The medium noise of Tex E was nearly equal to that of non Tex, but the noise of Tex J was much higher than that of Tex E at 50 kFCI. The magnetic domains in the transition region were observed by using MFM. The resulting MFM image of Tex J shows that there were more irregular magnetic domains in the region than in non Tex and Tex E. This irregularity caused the large medium noise in Tex J. TEM images show that the magnetic layers on the micro-bumps are physically separated from each other. Therefore, the magnetic clusters correspond to the micro-bumps. Tex J has big magnetic clusters, while Tex E has smaller ones.
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M. Sato, K. Yoshikawa
1996 Volume 20 Issue 2 Pages
69-72
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The magnetic properties of Zr/CoNiCr alloy/Cr heattreated media using a NiCuP electroless plated aluminum alloy (NiCuP/Al) substrate, which is non-magnetic before and after heat treatment, were investigated in comparison with those of similar media using a carbon substrate. The coercivity increased with increasing heat treatment temperature and heat treatment time, and a high coercivity of 3000 Oe was obtained after heating at 440°C for l0 minutes.From the results of Auger electron spectroscopy analysis, it was found that Cr diffused from the Cr underlayer into the CoNiCr alloy layer as the heat treatment temperature and heat treatment time increased, as in the carbon substrate. Both before and after heat treatment, the coercivity of the media using a NiCuP/Al substrate was higher than that of the media using a carbon substrate.
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T. Doi, K. Tamari
1996 Volume 20 Issue 2 Pages
73-76
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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NiO underlayer with a <100> orientation were prepared on a glass substrate by reactive rf sputtering at ambient temperature. Fe
3O
4 and CoO multilayers were grown epitaxially on the underlayer at 200°C; the Fe
3O
4 and CoO on the NiO underlayer grew along the <100> axis irrespective of the bilayer thickness. <100> oriented Co-γFe
2O
3 films [Co-γFe
2O
3/NiO] with perpendicular magnetic anisotropy were obtained after annealing of the multilayers in air at 280-350°C. The squareness ratio compensated by a demagnetization coefficient and the anisotropy energy of Co-γFe
2O
3/NiO were 0.94 and 1.4 × 10
6erg/cm
3, respectively; these values were larger than those of the CoγFe
2O
3 on the glass substrate (0.85 and 1.1 × 10
6erg/cm
3, respectively). The coercivity of CoγFe
2O
3/NiO increased with the Co content and could be controlled in the region of 0.8-5.0 kOe.
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K. Saito, N. Honda, K. Ouchi
1996 Volume 20 Issue 2 Pages
77-80
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The magnetic domain structures of Co-Cr films for per- pendicular recording media sputter-deposited at high Ar pressures (70 Pa) were investigated and compared with those of films deposited at low Ar pressures (0.2 Pa). The relationship between the magnetic domain structures and the medium noise was also studied. Co-Cr films deposited at high Ar pressures and at room temperature have a cluster-like magnetic domain structure, while those deposited at low Ar pressures and at room temperature have a maze-like magnetic domain structure. The magnetic domain size is much larger than the grain size in low- temperature-deposited films, whereas the sizes are comparable in high-temperature-deposited films. With increasing deposition temperature, the domain size becomes smaller, approaching the grain size. It was found that low medium noise corresponds not to smaller domain size, but to the strength of the longer wavelength component of the mag- netic domain in the dc remanent state.
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K. Harada, N. Honda, K. Ouchi
1996 Volume 20 Issue 2 Pages
81-84
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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Etching modes obtained by immersion in diluted acid were studied for Co-Cr films deposited under various sputtering conditions. It was found that the films deposited at a higt Ar pressure of 70 Pa exhibited a much lower etching rate than films deposited at a lower pressure. The lowest etching rate was obtained for films deposited at 70 Pa and at room temperature. The origins of etching modes are discussed in terms of the microstructure and Cr micro- segregation in the films, along with the changes in the magnetic properties of the films.
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K. Tan, I. Tagawa, Y. Nakamura
1996 Volume 20 Issue 2 Pages
85-88
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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We have already reported that the domain structures of soft-magnetic thin films can be simulated by using a pro- gram based on the Monte Carlo method. However, to match the simulated results with those obtained experimentally, the domain wall energies were assumed to be larger than those expressed by the analytic equation. In this paper, to remove this problem, the wall energies are calculated exactly and directly by computer simulation. A vortex state energy is also introduced. As a result, we obtain good agreement on the domain structures between simulation and experiment.
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Y. Shimizu, I. Tagawa, Y. Nakamura
1996 Volume 20 Issue 2 Pages
89-92
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The spacing loss characteristics of submicron-track recording were investigated by using a three-dimensional simulation program in perpendicular and longitudinal magnetic recording. The conventional spacing loss theory does not apply to the case where the track has submicron width. The playback spacing loss of a ring head increases as the track width is reduced, because of the wide fringing field on the track edge of a ring head. When the spacing is very small, submicron-track-width recording is possible in perpendicular recording. In the case of longitudinal recording, a head with a very narrow gap and contact recording are needed for submicron-track-width recording.
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K. Ajiki, A. Sato, F. Watanabe, M. Yanagisawa
1996 Volume 20 Issue 2 Pages
93-96
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The authors studied the effects of the slider mass and load force on the head jumping height in contact recording. The experiments were performed by using a contact-type model head and a measurement system consisting of an LDV and a piezo actuator. It has shown the results as follows. The jumping height decreased with an increase in the loading force. The jumping height had a complex dependences on the slider mass and load force. It was reduced for a slider of more than 1.0 mg under a suitable loading force. Lubrication lowered the jumping height. As regarding the jumping height, these findings suggest that, it is possible to design a contact recording head-disk interface (HDI) by using a high-mass slider such as conventional ones.
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A. Sato, K. Ajiki, F. Watanabe, M. Yanaglsawa
1996 Volume 20 Issue 2 Pages
97-100
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The authors investigated the effects of the slider mass and load force on both the jumping height and the wear of the contact pad for contact recording, using simulation and vibration energy experiments. The wear characteristics were determined by comparing the simulation results with those of the acoustic emission experiment, using a spherical contact pad with Hertz's contact. It was found that a low load leads to low wear on the contact pad. A high-mass slider, with a conventional magnetic head, can be used for contact recording. The use of liquid bearings with thick lubricant is an effective method for reducing highfrequency slider vibration.
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T. Ohtsu, N. Kushida, T. Iwakura, N. Kodama, S. Narishige
1996 Volume 20 Issue 2 Pages
101-104
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The write performance and off-track performance of inductive/MR thin-film heads with a wrap-around upper-pole write head are studied in comparison with those of conventional inductive/MR thin-film heads. The wrap-around write heads have a good overwrite perfomance equal to that of conventional write heads. The effective write-track width of conventional heads becomes smaller with an increase in the recording density. Howerver, it was found that the effective write-track width of wrap-around heads remains almost the same with an increase in the recording density, owing to the azimuth loss on the track side of the MR head in a read process. Therefore, inductive/MR thinfilm heads with a wrap-around upper-pole write head have the potential to provide magnetic recording with a higher TPI.
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S. Tsuboi, T. Korenari, N. Ishiwata, H. Matsutera, K. Tagami, S. Saito ...
1996 Volume 20 Issue 2 Pages
105-108
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The effects of recording heads on off-track noise characteristics were examined. It was found that an FeTaN head with a narrow gap and high
Bs was very effective for decreasing both on-track noise and off-track noise, in com- parison with a NiFe head with a narrow gap or a merged- type NiFe head with a wide gap. It was also confirmed that, according to readback waveform analysis and MFM images observation, the fluctuations of the magnetic transition in track-edge regions for magnetic patterns recorded by the FeTaN head were much smaller than for those recorded by the merged-type NiFe head with a wide gap. It will become increasingly important to improve recording heads as their track width becomes narrower.
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K. Ishihara, T. Suzuki, H. Yamamoto, K. Yamada
1996 Volume 20 Issue 2 Pages
109-112
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The characteristics of shielded-type spin-valve (SV) heads were simulated by using a micromagnetics model. The shields affect the magnetization distribution in the free layer which results in the reduction of the magneto-static coupling effect in the middle part of the free layer. For symmetric output waveform and high output level in the shielded-type SV heads, the pinned layer thickness is required to be as thin as possible to unify the magnetization distribution in the free layer along the MR height. A thick pinned layer cause a domain wall formation near the air bearing surface (ABS). Decreasing the MR height is effective for aligning the magnetization in the free layer toward the track width direction, and can improve the output waveform asymmetry. This is because the magneto-static coupling affects all over the free layer in the smaller height sensors.
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T. Ohtsu, M. Nakazawa, N. Kodama, K. Kawakami, S. Narishige
1996 Volume 20 Issue 2 Pages
113-116
Published: April 01, 1996
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The frequency response of the magnetic field intensity and the phase angle was calculated by using threedimensional dynamic magnetic field analysis of thin-film heads. The frequency response of the magnetic field with thinner high-
Bs core heads is better than that of conventional heads, because of the prevention of eddy current loss. It was found that the response of a head with a strong magnetic motive force is better than that of one with a weak magnetic motive force. This phenomenon is caused by magnetic saturation at the head core. This tendency becomes more marked with an increase of the write frequency. A head with a notch in the back gap region was also sutdied to prevent eddy current loss around the back gap. It was found thet a head with a notch is suitable for preventing eddy current loss around the back gap.
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H. Uchida, Y. Sonobe, Y. Ikeda, T. Toyooka
1996 Volume 20 Issue 2 Pages
117-120
Published: April 01, 1996
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The magnetization distributions for the magnetoresistive (MR) layer and the soft adiacent layer (SAL) in a shielded MR head were numerically analyzed by using the Landau-Lifshitz-Gilbert equation. The signal amplitude asymmetry (
As) dependences on the bias current (
Ib) and the saturation magnetization in the SAL (
MsSAL) were calculated to show that a symmetrical signal can be obtained for a certain
Ib by optimizing the
MsSAL value. The sensitivity for zero
As depends on the
MsSAL value, and a smaller
MsSAL value fives a higher signal sensitivity. For a large
MsSAL value, the SAL layer magntization is changed by the medium stray field, which reduces the effective field in the MR layer and the signal sensitivity. When the magnrtization in the SAL is in the vertical direction and that in the MR layer is in the 45-degree direction, the MR head shows the highest signal sensitivity and zero
As.)
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K. Kikuchi, T. Kobayashi, T. Kawai
1996 Volume 20 Issue 2 Pages
121-124
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The sensitivity profiles optimum bias field and transverse transfer curves of MR elements biased by a soft adjacent layer (SAL) were analyzed by using micromagnetic calculations. Four MR element structures, with different SAL magnetization configurations in the wing regions, were investigated. Additional peaks appeared at the base of the sensitivity profile when the elements had a SAL side wing capable of propagating the signal flux from the recording medium. The sensitivity increased and the optimum bias field decreased as the effective anisotropy field of the MR film was decreased by the MR element structures. When the MR element without a SAL side wing was under-biased, a hystersis arose in the MR response to a cycle of a transverse external field.
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T. Ishida, R. Sugita, K. Tohma, K. Yoshimoto
1996 Volume 20 Issue 2 Pages
125-128
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The noise characteristics of obliquely oriented thin-film tapes are investigated with regard to the head-to-medium spacing. The output spacing loss factor
K is estimated to be around 65 db for the normal head scanning direction. and around 85 db for the reverse scanning direction. The noise decrease is found inconsistent with the factor
K as the head-to-medium spacing increases. The separately recorded and reproduced noise spectra suggest that the head-to-medium spacing rather results in an increase in the noise component during the recording process. Assuming the spacing loss factor in the play-back process to be 54.6 db, such is found the more marked with a higher carrier frequency, indicating that the modulation noise dominated by the irregularity of the magnetic transition region increases with the transition width.
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T. Samoto, Y. Okazaki
1996 Volume 20 Issue 2 Pages
129-132
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The digital recording characteristics of a metal particulate tape (MP tape) with a thinner megnetic layer are investigated by a computer simulation based on the finite element method and a curling magnetization reversal model of the medium. We discuss the effect of the magnetic layer thickness of the medium on the recording and reproducing characteristics, namely, the reproduced voltage υs. wavelength property, the peak shift and asymmetry of a di-bit reproduced signal, and the nonlinearity of a recorded and reproduced signal response. The smaller magnetic layer thickness, which is approximately equal to a quarter of a wavelength gives the maximum reproduced voltage. The reproduced waveform asymmetry and the peak shift are reduced by using the smaller magnetic layer.
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K. Ishikawa, T. Nakayama, E. Miyashita, R. Taguchi, J. Numazawa
1996 Volume 20 Issue 2 Pages
133-136
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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In principle, it is possible to realize high-density recording on perpendicular magnetic recording media, It is expected that these media will be developed for recording use with high-definition television (HDTV) and high-quality video multimedia. A Co-Cr-Ta tape with a smooth base sheet was prepared in order to study the possibility of recording by facing-targets sputtering (FTS). The base sheet surface was observed by atomic force microscopy (AFM). The recording characteristics of Co-Cr-Ta tapes with smooth and standard base sheets were investigated at short wavelengths by using a drum tester (a system that evaluates the head and medium). The output with the smooth version was 3.2 dB higher at 170 kFRPI than with the standard one. A C/N
t value of 52.3 dB was obtained. The magnetization recorded on the smooth version at 250 kFRPI was clearly observed as a magnetic force microscopy (MFM) image.
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T. Andou, S. Yamamoto, H. Kurisu, M. Matsuura, T. Doi, K. Tamari
1996 Volume 20 Issue 2 Pages
137-140
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The pass-wear durability and recording characteristics of Co-γFe
2O
3 perpendicular magnetic recording thin-film disks were measured by using a MIG-type ring head with a gap length of about 0.2μm in contact sliding use. Co-γFe
2O
3 perpendicular magnetic anisotropy films were pre- pared by annealing CoO/Fe
3O
4 multilayers deposited onto an NiO underlayer in air at 280-350°C The Co-γFe
2O
3 perpendicular hard disk had no protective overcoat layers. The head wear was drastically improved by introducing a liquid lubricant. Reproduction demagnetization did not occur, and no damage or scratches were found after more than eighteen million passes. A
D50 of 180 kFRPI and a low-density reproduced voltage of 143 nV
p-p/{turu-pm- (m/s)) were obtained for a Co-γFe
2O
3 disk with an optimized film thickness and perpendicular coercivity. It is con- eluded that the Co-γFe
2O
3 perpendicular disks are suitable for ultra-high density recording media used in contact re- cording without an overcoat layer.
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Y. Kurokawa, A. Nagasaki, T. Homma, T. Osaka
1996 Volume 20 Issue 2 Pages
141-144
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The peak shift characteristics of perpendicular-longitudinal composite media in combination with a ring-typehead were investigated. It was found that the composite media had excellent peak shift characteristics in the region where the underlayer-medium showed worse characteristics. In the case of the composite media, strong perpendicular magnetization of the perpendicular recording layer suppressed the unfavorable effect of the underlayer. The underlayer's magnetization had great influence on the peak shift characteristics of the composite media, especially in the higher recording region. It is suggested that the peak shift characteristics are mainly subject to the condition of perpendicular magnetic reversal formed in the composite media.
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K. Takano, H. Muraoka, Y. Nakamura
1996 Volume 20 Issue 2 Pages
145-148
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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We designed and fabricated some samples of the contact magnetoresistive/inductive heads that have recently been developed for perpendicular magnetic recording, and evaluated them with a double-layered hard disk. A shielded MR head with shield-to-shield spacing of 0.5μm had a high
D50 of 170 kFRPI at a relative velocity of 1 m/s. On the other hand, the low-density output of the unshielded MR head was larger than that of the shielded head. With an increase in the recording density, however, the output gradually decreased, becoming roughly equal to that of the shielded-type in the high-density region. Thus, both shield- ed-type and unshielded-type MR heads had a good highdensity characteristics in the contact state.
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N. Jiang, H. Muraoka, Y. Nakamura
1996 Volume 20 Issue 2 Pages
149-152
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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A novel single-pole-type head with two head units each containing a submicron trackwidth pole is presented. The new head consists of three layers of thin-film conductors sandwiching the two main poles. The recording performance of the head is described. There is no noticeable interference between the two head units when they are separated by about 1μm, and they can work independently. The recorded trackwidth is confirmed to be about 0.5 μm by magnetic force microscopy. The linear densities written up to 150 kFRPI are visualized as MFM images.
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L. Zhang, M. Matsumoto, A. Morisako, T. Haeiwa, S. Takei, K. Oana
1996 Volume 20 Issue 2 Pages
153-156
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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Finite element magnetic field analysis is one the best tools for designing magnetic recording heads and arriving at a better understanding of the various phenomena associated with them. This paper describes the modeling of a metal-in-gap(MIG) magnetic recording head using the 2-D finite element method, and various analyses carried out on the basis of this modeling. It was confirmed that an MIG head, owing to the effect of its metallic layer, generates a much steeper magnetic field gradient than a ferrite head and alleviates the saturating characteristics of the magnetic field in relation to the magnetomotive force. The optimized thickness of the metallic layer deposited on one side of the gap is 0.4-1.0μm for a frequency lower than 10 MHz.
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Y. Kikuchi, R. Yahata, F. Aruga, Y. Fujita, A. Morisako, M. Matsumoto
1996 Volume 20 Issue 2 Pages
157-160
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The contour effect of a magnetic head was analyzed by the finite element method, and a new type of head with a reduced contour effect was fabricated on the basis of the simulation described in this paper. Few studies of the contour effect of a magnetic head have used the finite element method. The core shape and the position of the shielding case were simulated to improve the contour effect. The following results were obtained: (1)the level in the contour effect depends mainly on both the position and size of the shielding case; (2)the phase in the contour effect depends on the core shape; and (3) a new head was fabricated with a contour effect of less than 5 dB in the frequency range from 20 Hz to 50 Hz.
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S. Yanase, T. Kiya, N. Honda, K. Ouchi
1996 Volume 20 Issue 2 Pages
161-164
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The recording performances of Co-Cr-Nb and Co-Cr-Ta perpendicular media were studied along with their noise properties. Single-layer media were recorded by using a ring head. The Co-Cr-Nb and the Co-Cr-Ta media exhibited a similar high-density response, showing a maximum reproducible density of 720 kFRPI. It was found that the noise level for Co-Cr-Nb media was lower than that for Co-Cr-Ta media by a factor of 5 dB. MFM images of recorded medium surfaces are much clearer and more homogeneous for a Co-Cr-Nb medium than those for a Co-Cr-Ta medium, corrersponding to the noise properties.
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T. Tomura, O. Kamada, N. Itoh, H. Minemoto
1996 Volume 20 Issue 2 Pages
165-168
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The influence of the irreversible magnetization process of the stripe domain on the linearity error in (BiGdLaY)
3(FeGa)
5 O
12 films for optical magnetic field sensors is studied. The domain period and wall coercive force were determined by measuring the applied field dependence of the angle at which the light beam is diffracted by the periodic magnetic domain structure. The magnetization curves calculated according to the modified stripe domain theory, incorporating wall coercivity, showed good agreement with the experimental results as regards the AC output characteristics, especially a large linearity error in the very small external field region.
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Y. Mino, K. Ando, H. Matsuhata, Y. Yokoyama, S. Onari
1996 Volume 20 Issue 2 Pages
169-172
Published: April 01, 1996
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Microcrystals of the diluted magnetic semiconductor Cd
1-xMn
xTe(
x=0.13,0.16) were fabricaed by the laser ablation method to investigate the formation process of the microcrystals and their magneto-optic effect. Microcrystals 20-40Å in diameter were observed by scanning tunneling microscopy and transmission electron microscopy. In the initial stage of the microcrystals' frowth, they had forms like circular plates. As the Cd
1-xMn
xTe evaporation increased, they became larger and rounder. X-ray diffraction showed the mixing of zinc-blende and wurtzite structures. The magnetic circular dichroism (MCD) spectra of the microcrystals were different from those of Cd
1-xMn
xTe thick films. The MCD peak, which reflects the band gap,shifted to a higher energy as the diameter of the microcrystal decreased. This energy shift was analyzed by using a quantum confinement model.
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T. Katsuyama, T. Ide, T. Kawase, S. Nebashi, T. Shimoda
1996 Volume 20 Issue 2 Pages
173-176
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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To investigate the effect of birefringence on noise, we studied the noise in magneto-optical media by means of alternating phase difference of the optical head. We examined the effect of a tilted ellipsoid near the bottom of the substrate in the vicinity of the groove, and the effect of vertical birefringence and a beam illuminating the disk in which the groove was molded. As a result, we found that the MO media noise was caused by irregularity of the groove shape and by elliptic polarization of the vertical birefringence.
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M. Ogawa, M. Nakada, M. Okada, M. Itoh
1996 Volume 20 Issue 2 Pages
177-180
Published: April 01, 1996
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A method for analyzing the light scattered from magnetic materials was developed for Land/Groove recording by using The products of the scattering light intensity and Kerr rotation (
R·θ) were calculated function of the land or groove width. The calculation results show that the
R·θ of a land is larger than that of a groove for TM-polarized light, and vice versa for TE-polarized light. The measured track pitch dependence of the carrier level agreed with the calculation results. In Land/Groove recording, in terms of carrier level and crosstalk, TM-polarization is than TE-polarization when a land is reproduced, and TE-polarization is better when a groove is reproduced.
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H. Ikekame, Y. Morishita, K. Sato
1996 Volume 20 Issue 2 Pages
181-184
Published: April 01, 1996
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Ferromagnetic MnSb thin films were grown on GaAs (100) substrates by the hot-wall epitaxy (HWE) technique using polycrystalline powders of MnSb as an evaporation source. The source and substrate temperatures were 650-700°C and 300-500°C, respectively. The (10.1) oriented MnSb films of nearly stoichiometric composition were grown on (100) GaAs. The polar magneto-optical Kerr rotation and ellipticity spectra were measured in the films, and showed almost the same spectral shape as that reported previously in bulk single crystals, except that the magneto-optical effect of the films was larger in the high-energy region than that of the single crystals.
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N. Itoh, H. Minemoto, D. Ishiko, S. Ishizuka
1996 Volume 20 Issue 2 Pages
185-188
Published: April 01, 1996
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We developed highly accurate optical magnetic field sensors. The sensor optical system has a confocal optical system using ball lenses. Bi-substituted rare earth iron garnets were prepared by the LPE method for use as Faraday rotators. We found that a new garnet composition, Bi
1.14Gd
0.57La
0.02Y
1.27Fe
4.53Ga
0.47O
12, showed stable temperature characteristics of the sensitivity; The temperature dependence of the sensor output was less than 2.0% from -20°C to +80°C. We also improved the linearity error in the small magnetic field by using the film thickness dependence of the wall coercive force. The linearity error of the sensor output was within 1.0% for alternating magnetic fields from 3.0 Oe to 420 Oe. The sensors achieved high performance with regard to the linearity and the temperature characteristics.
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Y. Yokoyama, T. Hirano, W. Zaets, Y. Aiura, Y. Suzuki, K. Ando
1996 Volume 20 Issue 2 Pages
189-192
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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Magneto-optical effect and electrical resistivity of Sr doped LaMnO
3 films and Bi-doped La
0.8Sr
0.2MnO
3 films prepared by a laser deposition technique were measured. Measured magnetic circular dichroism (MCD) spectra are analyzed by fitting with dispersive dependence of charge transfer transition. In Sr-doped LaMnO
3 films the structures between 3 and 5 eV in MCD spectra are ascribed to charge transfer transitions from O2p to Mndγ(
eg). The energy shift of those structure is discussed with a model of the change of energy band width arising from the spin orientation. In MCD spectra of Bi-doped films newly transition around 3.5 eV appears and largely shifts to lower energy. Metalinsulator transition by Bi-doping may arise from not Bi multivalence but from the change in Mn-O-Mn bonding angle.
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N. Okuzawa, T. Katayama, D. Fujitani, W. Geerts, Y. Suzuki
1996 Volume 20 Issue 2 Pages
193-196
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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Measurements of polar magneto-optical (MO) Kerr spectra of hcp-CO films with various orientations fabricated by the molecular beam epitaxy (MBE) method were carried out. Substrate used here was MgO(100) and (111) surfaces with Au and Ag buffer layers. The CO films were covered with 20Å Au cap layer to prevent from oxidation. The MO Kerr spectra were different to each other between the (1120) and (0001) planes in the low-energy region, below 4.0 eV. This suggests that the electronic states are modified by the magnetization directions through a spin-orbit coupling.
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K. Sato, T. Kondo, J. Abe, H. Ikekame, M. Sano, S. Mitani, K. Takanash ...
1996 Volume 20 Issue 2 Pages
197-200
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The spectra of the magneto-optical Kerr effect and optical constants were measured in artificially ordered superlattices consisting of 1 to 5 monoatomic layers of Fe and Au. The Kerr rotation spectra showed a prominent structure around 4 eV, which undergoes a shift with layer thickness, the spectral features being quite different from those calculated by the virtual optical constant method which assumes that the superlattice is composed of pure metallic layers. This result suggests the formation of a new ordered alloy with a period extending up to 5 mololayers, which do not exist in the binary phase diagram of thermal equilibrium. The magneto-optical structure around 4 eV is attributed to the Au 5d → Fe 3d transition, on the basis of results of the energy band calculation.
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A. Yamaguchi, A. Yamamoto, S. Iwata, S. Tsunashima
1996 Volume 20 Issue 2 Pages
201-204
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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Sputtered AuCo alloy films with Co content below 48 at% showed an fcc non-equilibrium alloy phase. The measured optical constants,
n and
k, of Au
56Co
44 film were similar to those of Co-bulk rather than Au-bulk. The off- diagonal components,
ω·σ'xy and
ω·σ''xy (
σxy=
σ'xy+i
σ''xy), of the conductivity tensor were estimated from the optical constants and magneto-optical Kerr spectra of the alloy film. While the spectrum of the
ω·σ''xy for the alloy film is also similar to that of Co-bulk, the peak position in the high- energy region shifts to a lower energy than in Co-bulk. The Kerr spectra of Au /Co / Au sandwiched and multilayer films were simulated by the effective reflectivity method, using the conductivity tensor for pure Co and Au together with that for AuCo alloy film. Assuming the formation of an alloy layer with a thickness of 5Å at the interface, the measured Kerr spectra of the sputtered multilayer films agreed well with the calculated ones.
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H. Saito, Y. Sogame, T. Kutsuna, S. Ishio
1996 Volume 20 Issue 2 Pages
205-208
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The effect of the tip-sample arrangement and tip-sample spacing on MFM images of magneto-optical disks was examined.When the magnetic moment of the tip was tilted with respect to the normal direction of the sample surface,the positions of recorded marks were found to be moved in a direction normal to the tip's tilted axis, owing to the contribution of the parallel component of the tip's magnetic moment with respect to the sample surface. With an increase in the tip-sample spacing, the recorded marks changed from donut-shaped to dome-shaped, and their size also changed. These results were consistent with the calculated magnetic force gradient for an MO disk sample. The evaluation method of recorded mark size was discussed.
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K. Kojima, T. Takahashi
1996 Volume 20 Issue 2 Pages
209-212
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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Hydrogen decrepitation (HD) method is reported to produce Sm
2Fe
17 phase with the particle size of 2-3 mm. Production of fine powder having below 1 mm is difficult with HD method. Present study found that, however, high pressure of hydrogen gas above 3.9 MPa can produce fine powder with the particle size below 150 μm in 90 wt%. The success of producing fine powder is attributed to reduction of hydrogen absorption temperature.
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R. Murakami, K. Shima, H. Takamura, T. Tanaka, M. Okada
1996 Volume 20 Issue 2 Pages
213-216
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The apparent phases and magnetic properties of ferrites of the RE
2O
3-AM
2O-Fe
2O
3 system (RE=Y, La, Ce, Pr, Nd, Sm, Gd, and AM=Na, K, Rb) were studied. The observed phases were classified according to the combination of rare earth metal and alkaline metal. M-type ferrites, which have a magnetoplumbite structure, were obtained in the La
2O
3AM
2O-Fe
2O
3system (AM=Na, K, Rb). M-type ferrites were synthesized at over 1473 K for the La-Na system, 1573 K for the La-K system, and 1673 K for the La-Rb system. A single phase of M-type ferrite was prepared in (La
1-xK
x)O·6Fe
2O
3 at
x=0.2. The magnetization of (La
0.8K
0.2)O·6Fe
2O
3 is 86μWb·m·kg
-1,and the Curie temperature is 708 K.
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H. Matsunaga, M. Okita, S. Mino, N. Ishigaki
1996 Volume 20 Issue 2 Pages
217-220
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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High-energy-compaction-molded bonded magnets, composed of anisotropic Nd-Fe-B powder and epoxy resin, were developed. The influence of the binder on the magnetic properties and the degree of magnetic orientation was investigated. The results show that the frictional force between powders is decreased by warm-compaction molding and by using a binder with low melt viscosity. Magnets made by this method have a powder volume fraction and degree of magnetic orientation of 78.1% and 97.6%, respectively; these values are significantly higher than those for a cold-compaction-molded magnet. In order to suppress thermal degradation of the magnetic powder in the curing process, an epoxy resin that can be cured at 120°C was used for bonding. The (
BH)
max of a typical bonded magnet is 20.3 MGOe, which is 58.5% of the value for the powder.
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A. Kitazawa, T. Ishibashi
1996 Volume 20 Issue 2 Pages
221-224
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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High-performance bonded magnets composed of Sm
2Co
17 powder mixed with Sm
2Fe
17N
x powder were developed. This is an important technology using the magnetostatic interaction between Sm
2Co
17 and Sm
2Fe
17N
x particles. The interparticle interaction (IPI) is estimated by the mean field approximation. IPI suppresses the magnetization reversal of Sm
2Fe
17N
x particles, and increases the alignment of both types of magnetic particles. The amount of IPI is influenced by the magnetic properties of each powder, which necessarily must be homogeneously dispersed. With proper adjustment of the preparation conditions, the magnetic properties of mixed bonded magnets are
Br=10.1 kG,
iHc= 12.6 kOe, and (
BH)
max=22.6 MGOe. The temperature coefficients of
Br and
iHc in this magnet are -0.05%/°C and -0.26%/°C, respectively, which are comparable with those of Sm
2Co
17.
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H. Nishio, S. Hashimoto, K. Yajima, A. Fukuno
1996 Volume 20 Issue 2 Pages
225-228
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The effects of Sn addition on the magnetic viscosity coefficient S
v of Nd-Fe-B sintered magnets (Nd
12.1DY
2.0Fe
78.8Al
0.9Sn
0.1B
6.1) were examined in the temperature range from 300 to 483 K. The relationship between S
v and the temperature variation of the coercive force
ΔHcJ/
ΔT was studied. This experiment showed that
ΔHcJ/
ΔT and α(
HcJ)decreased as S
v decreased. Addition of Sn to Nd-Fe-B sintered magnets reduced S
v by about 1/2 at 300 K, and S
v gradually increased with the temperature, in contrast to the tendency in Sn-free Nd-Fe-B sintered magnets. Addition of Sn to Nd-Fe-B sintered magnets was effective in reducing
ΔHcJ/
ΔT and α(
HcJ) because of the marked decrease in S
v at 300 K.
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H. Yamamoto, T. Oohira, K. Takahashi
1996 Volume 20 Issue 2 Pages
229-232
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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An experiment was carried out to investigate the magnetic and physical properties of Sm-Fe-Ga-N and Sm-FeCo-Ga-N compounds. These compounds were prepared by nitrogenation of Sm
2Fe
17-xGa
x and Sm
2 (Fe
0.9Co
0.1)
16.7 Ga
0.3 powders (about 30
μm) in high-purity nitrogen gas at pressures of 4.9 MPa, and temperatures of 475-600°C for 1-4 h.It was found that the value of the anisotropy field (
HA) in Sm
2Fe
17-xGa
xN
y compounds increased with increasing Ga concentration (up to
x=0.3), while the saturation magnetization (
σs) decreased. The values of
HA and
σs in nitride of Sm
2Fe1
6.7Ga
0.3 were 9.95 MA/m and 188.5 Wb· m/kg, respectively.The magnetic and physical properties of an anisotropic Sm
2Fe
16.7Ga
0.3N
3.36 epoxy-bonded magnet were(
BH)
max=93.1 kJ/m
3and
D=5.36 Mg/m
3. It was found that the value of the Curie temperature, and the reversible temperature coefficients of the bonded magnet in Sm-FeCo-Ga-N compounds were better than those of Sm-Fe-Ga-N compounds.
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A. Kojima, F. Ogiwara, A. Makino, A. Inoue, T. Masumoto
1996 Volume 20 Issue 2 Pages
233-236
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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The magnetic properties and structure of nanocrystalline Fe-(Nb, Zr)-R-B (R=Pr, Nd) melt-spun alloys with high Fe concentrations were investigated. A nanocrystalline Fe
88 Nb
2Pr
5B
5 alloy obtained by annealing an amorphous phase exhibits a coercive force (
iHr) of 216 kA/m, remanence (
Ir) of 1.23 T and a maximum energy product((
BH)
max) of 110 kJ/m
3, which exceed those for nanocrystalline Fe
88Nb
2Pr
5B
5 alloy directly obtained by melt quenching. Fe
98-x-y(Nb, Zr)
2-R
xB
y (4≤
x≤7, 3≤ ≤
y7 (at%)) alloys consist of an amorphous phase in as-quenched state and the amorphous phase gives way to nanoscale bcc-Fe and R
2Fe
l4B
1 phases upon annealing at temperatures between 973 and 1073 K. The alloys exhibit high
Ir above 1.2 T in a region with high Fe and low R concentrations, and high
iHc above 250 kA/m in a region with high R and B concentrations. High (
BH)
max values are obtained for the high-
Ir alloys and exceed 90 kJ/m
3 in the region where the Pr and Nd concentrations are below 5 at% for Fe-Nb-R-B systems.
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H. Aoyama, Y. Honkura
1996 Volume 20 Issue 2 Pages
237-240
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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Sputtering conditions are investigated in order to deposit Fe-Pt thick film magnet. Argon pressure, input power, and target-substrate distance are determined to obtain a high maximum energy product film. Under the conditions, a film of 129μm thickness with a maximum energy product of 104 kJ/m
3 (13.1 MGOe) is obtained. Examination of the microstructure indicates that the small grain size gives a better coercive force than that of bulk material. The obtained magnetic properties are considered to be sufficient for certain applications of micro-machines.
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S. Takei, A. Morisako, M. Matsumoto, T. Haeiwa, S. Shomura, Y. Minemur ...
1996 Volume 20 Issue 2 Pages
241-244
Published: April 01, 1996
Released on J-STAGE: October 24, 2007
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SmCo alloy thin films were prepared by means of a dc magnetron sputtering apparatus with a composite type of target at various substrate temperatures, with the number of Sm chips adjusted so that a stoichiometric content of SmCo
5 could be obtained in the films. It was found that SmCo
5 thin film with maximum coercive force was formed at 350°C. SmCo films deposited on a Cr underlayer at the substrate temperature of 300°C exhibit maximum coercive force and a higher squareness ratio than those without a Cr underlayer.
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