Michiyori Miura

Annealing behavior of magnetic anisotropy in CoNbZr films

The effect of magnetic and nonmagnetic annealing on the magnetic anisotropy in CoNbZr films, formed by a DC opposing-targets sputtering method, was investigated. It was revealed that the origin of the magnetic anisotropy is the directional ordering of the magnetic atoms. The anisotropy fields and the direction of the easy axis obtained when the films are annealed in zero magnetic field are almost the same as those for the magnetic field parallel to the easy axis of the as-deposited films. When the films are annealed in a magnetic field perpendicular to the easy axis, the anisotropy field induced in parallel with the magnetic field, H/sub k/(t), is well represented by the following formula: ln (1-H/sub k/(t)/H/sub k/( infinity ) varies as - square root Tt, where H/sub k/( infinity ) is the thermal equilibrium value of the anisotropy field and D is the diffusion constant. The activation energy of the as-deposited film is 0.86 eV. Annealing the film increases the activation energy which is 2.1 eV when the film is annealed at a temperature of 450 degrees C for 2 h. >

Magnetic and Crystallographical Characteristics of the Sendust Films formed by DC Opposite Sputtering Method

Sendust films were formed using DC opposite sputtering equipment. Then, sputtering conditions that influcne the magnetic and crystallographical characteristics of the films were studied. Sendust films with a low coercive force ( 1000 at 6 MHz) are formed under the conditions of high sputtering gas pressures and high substrate temperatures. As the deposition rate increases, a higher substrate temperature is necessary to form films with low coercive forces. Superlattice formation and large columnar crystallites are found in the films formed at high sputtering gas pressures and high substrate temperatures; they decrease the coercive forces of the films.

Anomalous magnetic behaviour of nanocrystalline FeTaC films at high temperature

The magnetic properties of nanocrystalline Fe/sub 79/Ta/sub 10/C/sub 11/ films with different crystallographic characteristics are studied. The soft magnetic properties are not related to the Fe characteristics, but are closely related to the TaC characteristics, such as the lattice parameter and grain size. The film, composed of fine TaC grain with a small lattice parameter, has excellent soft magnetic characteristics at room temperature and its magnetic properties change little with temperature. On the contrary, the film composed of large TaC grain with a large lattice parameter has a large coercive force and magnetostriction at room temperature and exhibits a anomalous magnetic behavior at high temperature. The coercive force at 300 degrees C becomes ten times larger than that at room temperature. This phenomenon is most likely caused by the disappearance of the intergranular ferromagnetic coupling. >

Crystallographic and magnetic behavior in crystallization process of FeTaC film

We have studied the crystallographic and magnetic behavior of amorphous Fe/sub 79/Ta/sub 10/C/sub 11/ films during the crystallization process. The crystallization process starts with the precipitation of Ta or TaC/sub 1-x/. The saturation magnetizations of the film and Fe grain size increase at the same time. The increase in saturation magnetization is completed at /spl sim/480/spl deg/C, Fe and Ta phase separation seem to be completed at this temperature. The anomalous state appears between 480 and 530/spl deg/C, in which good soft magnetic properties do not appear at room temperature, although the Fe grain size is small enough. The source of this phenomenon is the weak intergranular ferromagnetic coupling caused by the formation of a magnetic material with a low Curie point at the Fe grain boundary.

High M/sub r/ squareness and exchange decoupled perpendicular recording media

CoCr/sub 15/Pt/sub 13/ perpendicular layers with CoCr-alloy/Ti dual underlayers were annealed and it was investigated how the dual underlayer structure influences the characteristics of the CoCrPt perpendicular layer. The Ti layer thickness has a remarkable influence on the Cr diffusion efficiency from the upper underlayer of the dual underlayer into the CoCrPt perpendicular layer. The Cr diffusion efficiency is improved by increasing the Ti layer thickness and the addition of Ta or Pt to the upper underlayer of the dual underlayer. As a result, the magnetic properties were greatly improved. For the CoCr/sub 15/Pt/sub 13/(40 nm)/CoCr/sub 30/Pt/sub 8/Ta/sub 2/(20 nm)/Ti(25 nm) media postannealed at 500/spl deg/C for 30 min., the coercivity and M/sub r/ squareness were 7100 Oe and 0.98 respectively. Also, the slope of the MH loop at coercivity was nearly 1/4/spl pi/.

A fabrication process of thin film heads for VCR

A novel magnetic head with thin-film magnetic yokes and thin-film coils for VCR systems has been developed. The head has 25- mu m-thick CoNbZr (B/sub s/=0.9 T) magnetic yokes with round edges. The lower yoke is buried in the groove with a round bottom formed by a combination of photolithographic and mechanical processing, while the upper yoke is formed by ion etching. The head with a 150 mu m gap depth has excellent recording performance on high H/sub c/ media (H/sub c/=1500 Oe). Its contour-signal level is below -45 dB from the main signal ( lambda =2.5 mu m). >

In-line double gap thin film head for the electronic still camera system

An in-line double gap head ( IDG head ) has been developed for the electronic still camera system. Excellent performance of the IDG heads can be achieved. The cross-talk level is about -45 dB and the carrier to noise ratio ( C/N ) is about 60 dB, which is at least +3 dB better than that of conventional ferrite heads. The IDG heads can record on metal powder media with gap depth as large as 10 µm, resulting in high tolerance of wear ( the wear life is 1000-5000 hours ).

Formation of CoNbZr films by a dc opposing-target sputtering method

CoNbZr films were prepared using dc opposing‐target sputtering equipment. It was investigated as to how the sputtering gas pressure influences the characteristics of the films under the condition of constant deposition rate. The saturation flux density and crystallization temperature were almost constant and independent of the sputtering gas pressure. Their values were 0.83±0.03 T and 562±1 °C. However, the anisotropy field, coercive force, and morphology of the films were significantly affected by the sputtering gas pressure.

Formation of Sendust Films by DC Opposite Sputtering Method

Sendust films were prepared using DC opposite sputtering equipment. Films with a low coercive force of 0.5 Oe and an initial permeability of 1300 at 6 MHz can be prepared at a deposition rate of 5.5 µm/h without annealing of the films after the deposition. The way in which sputtering conditions influence the coercive force of the films was also investigated.

Analysis of magnetostriction effect in ferrite heads

We made single crystal ferrite heads with various thermal stress by changing the annealing temperature, and we traced the source of the poor performance by experiments. As a result, we revealed that the deterioration of the ferrite permeability near the gap determines, in large part, the operating characteristics of the ferrite head. Considering the result, we developed a calculation method that enables us to estimate the relationship between head characteristics and magnetoelastic effect in ferrite heads.