Masatoshi Hayakawa

Induced magnetic anisotropy of Co‐based amorphous alloys

The effect of the rotating magnetic field annealing on high magnetic induction amorphous alloy Fe5Co75Si4B16 (TC≳Tx) was studied. Experimental results and the theoretical analysis gave the following conclusions. 1) Induced magnetic anisotropy is dispersed by the rotating magnetic field annealing. 2) The relationship between magnetic permeability μ and number of rotations R is given by the formula 3) The rotating field annealing is useful to eliminate the induced magnetic anisotropy, especially for the amorphous materials with TC≳Tx.

Magnetic and other properties and sputtering behavior of Co‐base amorphous alloy films

Magnetic and other properties of Co‐base amorphous alloy films prepared by sputtering are investigated. A detailed magnetic phase diagram with saturation magnetic flux density, crystallization temperature, and zero‐magnetostrictive line on Co‐Ta‐Zr amorphous alloys were obtained, and the technical knowhow to make a film with well‐reproducible characteristics by widely changing the sputtering conditions was related with these physical properties. Especially on alloy sputtering, a phenomenological model for elucidating a composition difference between film and target is presented. After these studies, the film characteristics of Bs=12 kG, Tx=450 °C, ‖λs‖<10−8, Hc<10 mOe, and permeabilities of μ(1 MHz)=7000, μ(100 MHz)=2000 for the single film of 2 μm in thickness and of μ(1 MHz)=4000, μ(100 MHz)=800 for the insulator‐sandwiched multilayered film of 10 μm are obtained, and these well‐balanced values enable us to apply the materials for high‐frequency recording head.

Soft magnetic properties of FeRuGaSi alloy films: SOFMAX®

To advance new soft magnetic materials of an FeGaSi alloy into the commercial world, improvements on various properties were designed by introducing additive elements without sacrificing its high saturation magnetic induction. The detailed studies on the diversified properties, such as saturation magnetic induction, film internal stress, wear resistivity, and so on, were performed. High‐frequency permeability of the laminated structure film was also investigated. As a result, the Ru‐added FeRuGaSi alloy films, whose typical compositions are Fe72Ru4Ga7Si17 and Fe68Ru8Ga7Si17 (at. %), prove to be excellent soft magnetic materials especially appropriate for the magnetic recording/playback head core use.

New crystalline soft magnetic alloy with high saturation magnetization (invited)

Extensive study was made on Fe‐base crystalline alloys in search for new soft magnetic materials with high saturation magnetization by means of sputtering technique. It revealed that newly found FeGaSi and FeAlGe alloy systems possessed excellent soft magnetic properties with remarkably higher saturation magnetization. These new alloy films, annealed in vacuum at 500 °C for 1 h, show the magnetic properties of Bs=13 and 15 kG, Hc=0.09 and 0.20 Oe, and μ1 MHz=2000 and 1800 for the FeGaSi and FeAlGe alloy films of 2 μm in thickness, respectively. These values are superior to those of FeAlSi (sendust) alloy which is a typical soft magnetic material with high saturation magnetization. Results of the Co‐added systems of FeCoGaSi and FeCoAlGe alloys are also presented. Discussions are given on various systems of Fe base crystalline alloy films studied, which are classified into four types of groups with respect to magnetic softness.

Soft magnetic Fe‐Al‐N/Si‐N multilayered film with high thermal stability

An attempt to obtain soft magnetic materials with high saturation magnetic flux density and thermal stability has been carried out with respect to a multilayered type of films containing Fe‐N prepared by two‐source magnetron rf sputtering. The addition of small amounts of elements such as Al is effective in improving soft magnetic properties of Fe‐N films. Multilayered films of Fe‐Al‐N intervened by thin Si‐N layers showed softer magnetic properties than the Fe‐Al‐N single layer films and also showed high thermal stability. Typically, Fe‐Al‐N (500 A)/Si‐N (12 A) multilayered films exhibited a saturation magnetic flux density of 20 kG, a coercivity Hc of 0.3 Oe, and a permeability μ of 1900 at 5 MHz after annealing at 550 °C for 1 h.

Soft magnetic properties for Fe-Al-Nb-N-O films

Magnetic and other properties of fine-crystal Fe-N films with additional Al, Nb, and O were investigated. Films were prepared by RF planar magnetron sputtering. The grain size and the lattice spacing were changed by the addition of Al and Nb, and the coaddition of Al and Nb was found to be effective in improving the soft magnetic properties of the films after annealing at 550 degrees C. Introducing oxygen into the sputtering gas of argon and nitrogen increased the nitrogen concentration in the films and was effective in reducing the coercivity of the films. The magnetostriction of the films changed from negative toward positive with increasing nitrogen concentration and crossed zero at the nitrogen concentration where the coercivity had a minimum value. Hardness measurement of the films revealed that the addition of Al and Nb prevents recrystallization in Fe films as well as in Fe-N-O films. The (Fe/sub 97.5/Al/sub 1.1/Nb/sub 1.4/)/sub 92/N/sub 6/O/sub 2/ films exhibited a saturation magnetic flux density of 20 kG, a coercivity of 0.3-0.5 Oe, and a hardness above 1000 even after annealing at 550 degrees C without magnetic field application. >

Characteristics of soft magnetic thin films for magnetic head core application

Abstract Recent developments of soft magnetic thin films are reviewed from the viewpoint of magnetic head core applications. Many kinds of alloy films with high saturation flux density over 1.0 T have been investigated in the last decade together with conventional materials such as Fe-Al-Si (Sendust) films and Co-based amorphous alloy films. Almost all reported materials with high saturation flux density are Fe-based alloy, Fe-based micro-crystalline alloy and multilayered alloy films. This paper briefly describes the advantage of soft magnetic thin films with high saturation flux density in high frequency operation to avoid the natural ferromagnetic resonance. The advantage of isotropic Fe-based alloy film is also described for a practical MIG head application.

Magnetostriction of Co-based amorphous alloys

Abstract Magnetostriction λ of Co-based amorphous alloys Fe x Co y Ni z Si p B q prepared by a rapid quenching technique was obtained by measuring the tension dependence of magnetic hysteresis loop at 8 Hz. The least squares fitting leads to λ ( x , y , z , p , q ) × 10 6 = 0.714 x − 0.0831 y − 0.306 z + 0.101 p + 0.0955 q in at %.

CoPtB(O) alloy films as new perpendicular recording media

In search of new hard magnetic materials with high saturation magnetization and large coercivity, a comprehensive study was made on numerous Co‐ and CoPt‐base crystalline alloys by means of sputtering techniques. It revealed that a newly found CoPtB(O) alloy system possessed excellent hard magnetic properties with remarkably large perpendicular coercivity and high saturation magnetization. This new alloy film, deposited onto room temperature substrates, shows the magnetic properties of 4πMs=12 kG, H⊥c=4000 Oe, and perpendicular anisotropy field Hk=22 kOe. These values are superior to those of prevailing materials such as CoCr perpendicular and CoPt or CoNi longitudinal recording media. The typical composition is Co69Pt20B6O5 (at. %), and oxygen plays a momentous role on the coercivity in this alloy film. As a magnetic recording medium, a write/read experiment of this film shows that the readout signal has a +9 dB peak‐to‐peak amplitude compared with that of metal particle tape at 1 μm wavelength and has +...

Auger spectroscopy analysis of metal/ferrite interface layer in metal-in-gap magnetic head

It is well known that a poor magnetic layer is formed at the interface between the metal film (e.g. Sendust) and the ferrite core in fabricating metal-in-gap heads. The authors have analyzed precisely the poor magnetic layer by means of Auger spectroscopy combined with ion sputtering. It is found that the poor magnetic layer is formed by reaction at the interface between the metal film and the substrate during the annealing process. In the case of Sendust, this layer is composed of Al/sub 2/O/sub 3/+SiO/sub 2/, which is a nonmagnetic material. For a new soft magnetic alloy, Fe-Ga-Si-Ru, used instead of sendust, the reacted layer is composed of SiO/sub 2//Ga/sub 2/O/sub 3/. To prevent the reaction, a very thin intermediate film of SiO/sub 2/ or Si-N-O was formed by sputtering. >