Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-12-28
2004-11-09
Chen, Tianjie (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06816347
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a magnetoresistive element and a magnetic recording apparatus, and more particularly, to a magnetoresistive element using a spin valve film including electron reflective layers on opposite surfaces of a non-magnetic intermediate layer, and a magnetic recording apparatus using this magnetoresistive element in its magnetic head.
Recently, for a higher density of HDD (hard disk drive), read elements with higher sensitivities are under development. Toward such purposes, researches are being made about elements using a giant magnetoresistance effect basically configured to interpose a non-magnetic conductive layer between two metal magnetic layers.
Hopeful one of those elements is an element having a structure called “spin valve”. This is an element interposing a non-magnetic layer between two metal ferromagnetic layers of which one ferromagnetic layer (called “magnetically fixed layer” or “pinned layer”) is fixed with a bias magnetic field, or the like, whereas the other ferromagnetic layer, not magnetically fixed, (called “magnetically free layer” or “free layer”) reads out the magnetic field from the recording medium and changes its magnetic orientation relative to that of the former magnetic layer, thereby to obtain a giant magnetic resistance (see Phys. Rev. B. Vol. 45, 806(1992), J. Appl. Phys. Vol. 69, 4774(1991), etc.).
Researches are also being made about a model using a multi-layered structure that is construction repeat of a non-magnetic layer between metal ferromagnetic layers to enhance the magnetoresistance effect. In these models, however, interaction between magnetic layers is great, in general, and they invite some problems when used in HDD, such as insufficient sensitivity to a medium magnetic field.
Various improvements were proposed and made for obtaining higher outputs with these multi-layered structures. Among them, what is most effective is to thin the magnetically free layer and the non-magnetic intermediate layer. By thinning these films, shunt diversion can be reduced and output can be improved. There has been proposed a spin filter/spin valve structure attaining both output enhancement by thinning films and bias point adjustment in head designing, a spin valve film having a resistance changing ratio (MR) around 9% and a magnetic head compatible with HDD having the surface density of 25 Gbpsi (gigabit per square inch) have been obtained.
In this structure, however, the maximum MR is less than 10%, and it is insufficient for coping with future recording densities of 40 Gbpsi or even more. Therefore, researches are continued toward new structures for further improved MR.
Among those structures, specular spin valves (SPSV) are currently the most hopeful structure. They are configured to stack an electron specular reflective layer on a magnetic layer to thereby elongate the mean free path so as to accomplish a structure equivalent to a magnetic multi-layered film and increase the resistance-changing ratio. Concerning this type of structure, heretofore reported are electron specular reflectance effects with oxide antiferromagnetic materials such NiO used as exchange bias films of magnetically pinned layers, amorphous Ta formed as a base layer of a magnetically free layer, or noble metal layers. There is also reported that MR is improved by electron reflection when oxide layers on the order of nanometer are formed in a magnetically pinned layer and a magnetically free layer (IEEE Trans. Mag., Vol. 33, No. 5, p3580, 9(1997), IEEE Trans. Mag., Vol. 32, No. 5, p4728, 9(1996)).
Among those conventional structures, those using an oxide antiferromagnetic material such as NiO as the exchange bias film involve the problem of a small exchange coupling force due to the natures peculiar to the materials. Additionally, when introducing a magnetically pinned layer having a synthetic antiferromagnetic structure, which is currently an indispensable structural item, electron reflection from the oxide exchange bias layer no longer contributes to MR, and the merit of MR improvement is lost.
Further, Ru (ruthenium) used in the coupling layer of a synthetic antiferromagnetic structure is a substance providing no electron reflecting effect. On the other hand, if amorphous Ta (tantalum) is used, it adversely affects good growth of films, and invites deterioration of soft-magnetic characteristics of the magnetically free layer, thermal stability of MR, thermal stability of magnetic pinning of the magnetically pinned layer and synthetic antiferromagnetic coupling.
Furthermore, if a noble metal or amorphous Ta layer is formed on the part of the magnetically pinned layer, magnetic coupling between layers on opposite sides thereof will be disconnected, and it is therefore inappropriate as a technique for obtaining electron-reflecting effects. For the purpose of maximizing MR, it is desirable that electron reflection occurs both in the magnetically free layer and the magnetically pinned layer.
The above-mentioned problem will be overcome with a method of making magnetic oxide layers of a thickness on the order of nanometer in the magnetically pinned layer and the magnetically free layer. This method, however, involves the problems, such as the need for a technically high-level process for making the oxide layer of a thickness on the order of nanometer, the need for a special processing apparatus, and the need for a time for fabrication.
As explained above, it is necessary for maximizing MR to make electron reflecting layers in both the magnetically free layer and the magnetically pinned layer, but the method of obtaining an electron reflection effect on the part of the magnetically pinned layer is currently only the method of making an oxide layer on the order of nanometer, and involved the problem that a high-level technique is required to make it.
SUMMARY OF THE INVENTION
The present invention has been made from recognition of those problems. It is therefore an object of the invention to provide a structure of a magnetically pinned layer ensuring a sufficient electron reflection effect on the part of the magnetically pinned layer, and a magnetoresistive element using a pin valve film including the structure.
In order to attain the object, a magnetoresistive element according to the invention includes a magnetically free layer, a magnetically pinned layer, and a non-magnetic intermediate layer interposed between the magnetically free layer and the magnetically pinned layer, wherein the magnetically pinned layer includes, at least, a first layer region disposed relatively remoter from the non-magnetic intermediate layer and a second layer region disposed relatively closer to the non-magnetic intermediate layer, and the first layer region is made of a ferromagnetic material containing a special additive element.
The additive element is one that can effectively change the electron potential of the magnetically pinned layer and can simultaneously maintain the crystal structure of the magnetically pinned layer. Usable as its additive element is any one selected from Cr (chrome), Rh (rhodium), Os (osmium), Re (rhenium), Si (silicon), Al (aluminum), Be (beryllium), Ga (gallium), Ge (germanium), Te (tellurium), B (boron), V (vanadium), Ru (ruthenium), Ir (iridium), W (tungsten), Mo (molybdenum), Au (gold), Pt (platinum), Ag (silver) and Cu (copper).
By addition of one or more of these elements, the magnetically pinned layer can be changed in electron potential, and electron reflection can be brought about along the boundary. Nb (niobium), Ta (tantalum), or other like materials, are not suitable as the additive elements because they change the crystal to microcrystal. Change of the crystal to microcrystal or amorphous form will adversely affects the crystallographic property of the film grown thereon.
For example, in case of a bottom spin valve having the magnetically free layer disposed above the magnetically pinned layer, since the crystalline property and orientation of the film formed above the first layer region to function as the electro
Fuke Hiromi
Fukuzawa Hideaki
Iwasaki Hitoshi
Kamiguchi Yuzo
Koi Katsuhiko
LandOfFree
Magnetoresistive element and magnetic recording apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetoresistive element and magnetic recording apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetoresistive element and magnetic recording apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3284974