Patent Application
20090073608
The instant nonprovisional patent application claims priority to Japanese Patent Application No. 2007-218566 filed Aug. 24, 2007 and which is incorporated by reference in its entirety herein for all purposes.
Magnetic disk drives (HDDs) allow an increase in information recording capacity, conversion speed, and reduction in error rates. Recent trends are toward greater magnetic recording densities. To meet these needs, research is underway into a scheme of recording, in which a magnetization direction of a recording film is perpendicular relative to a medium surface, which is what is called perpendicular recording, as compared with the longitudinal recording media that have conventionally been used. Practical application of perpendicular recording has already been started. In perpendicular recording, the higher the linear recording density, the less the demagnetizing field of the medium for more stabilized magnetization, which makes perpendicular recording suitable for higher recording densities. Known in perpendicular recording is, however, the problem of “erasure after recording”. This is a phenomenon, in which a recording head after a recording operation deteriorates recording signals on the medium. This is probably because remanent magnetization left in a main magnetic pole disturbs information recorded on the medium. Japanese Patent Publication No. 2004-199816 (“Patent Document 1”) proposes a use of a film stack of antiferromagnetically stacked ferromagnetic layers as the main magnetic pole in order to suppress erasure after recording.
To suppress erasure after recording, a known approach is to use, as the main magnetic pole, a film stack of a FeCo ferromagnetic layer and a nonmagnetic layer and the ferromagnetic layer is antiferromagnetically coupled to reduce remanent magnetization Mr of the main magnetic pole, thus decreasing squareness S.
If the number of nonmagnetic layers is increased to reduce the remanent magnetization Mr and thereby decrease the squareness S, however, a saturation magnetic field Hs increases, leading to a reduced current response characteristic of the head. If on the other hand, a film thickness of the FeCo ferromagnetic layer is decreased to reduce the remanent magnetization Mr and thereby decrease the squareness S, there is a shortage of a recording magnetic field, leading to a degraded overwrite characteristic. It is therefore important to reduce the remanent magnetization Mr of the main magnetic pole and thereby decrease the squareness S without changing the number of nonmagnetic layers or the film thickness of the FeCo ferromagnetic layer.
Embodiments of the present invention provide a perpendicular magnetic recording head suitable for high density recording that suppresses erasure after recording by reducing the remanent magnetization Mr of the main magnetic pole and thereby decreasing the squareness S. According to the embodiment of
Embodiments of the present invention relate generally to a perpendicular magnetic recording head and, more particularly, to a structure of a main magnetic pole.
It is an object of embodiments of the present invention to provide a perpendicular magnetic recording head suitable for high density recording that suppresses erasure after recording by reducing the remanent magnetization Mr of the main magnetic pole and thereby decreasing the squareness S.
To achieve the foregoing object, a perpendicular magnetic recording head according to an aspect of embodiments of the present invention includes a write head. The write head has a main magnetic pole piece, an auxiliary magnetic pole piece, and a coil. Specifically, the auxiliary magnetic pole piece is magnetically coupled to the main magnetic pole piece on a side opposite an air bearing surface. The coil generates a magnetic flux in the main magnetic pole piece and the auxiliary magnetic pole piece. Further, the main magnetic pole piece includes a multilayered film. The multilayered film includes a nonmagnetic layer, FeCo ferromagnetic layers, and NiFe soft magnetic layers. The nonmagnetic layer includes one or a plurality of elements selected from the group consisting of Cr, Ru, Rh, and Ir. The FeCo ferromagnetic layers are disposed above and below the nonmagnetic layer. The NiFe soft magnetic layers are inserted in the FeCo ferromagnetic layers in the vicinity sides of the nonmagnetic layer with respect to a center in a layer thickness direction of each FeCo ferromagnetic layer.
The FeCo ferromagnetic layers disposed above and below the NiFe soft magnetic layers are ferromagnetically coupled and the FeCo ferromagnetic layers disposed above and below the nonmagnetic layer are antiferromagnetically coupled.
Preferably, the NiFe soft magnetic layer is inserted in the FeCo ferromagnetic layer 1 to 7 nm away from the nonmagnetic layer.
A plurality of multilayered films may preferably be stacked one on top of another via a NiCr intermediate nonmagnetic layer.
The perpendicular magnetic recording head further includes a read head that has an upper magnetic shield, a lower magnetic shield, and a magnetoresistive sensor disposed between the upper magnetic shield and the lower magnetic shield.
In accordance with an aspect of embodiments of the present invention, the remanent magnetization Mr of the main magnetic pole piece can be reduced to thereby decrease the squareness S without changing the number of layers of the nonmagnetic layers or the film thickness of the FeCo ferromagnetic layer. This allows erasure after recording to be suppressed and a perpendicular magnetic recording head suitable for high density recording to be obtained.
A general structure of a perpendicular magnetic recording head according to an embodiment of the present invention will be described with reference to
A layer structure of the main magnetic pole piece 2 of the perpendicular magnetic recording head I according to the embodiment of the present invention will be described below with reference to
The above-described layer structure is characterized in that the NiFe soft magnetic layer 24 is inserted in each of the FeCo ferromagnetic layers 22 disposed above and below the nonmagnetic layer 26. The NiFe soft magnetic layers 24 are disposed in the vicinity sides of the nonmagnetic layer 26 with respect to a center in a layer thickness direction of the FeCo ferromagnetic layer 22. Labeling the FeCo ferromagnetic layer 22′ (the first to the fourth) between the NiFe soft magnetic layer 24 and the nonmagnetic layer 26 a FeCo layer adjacent the nonmagnetic layer. The FeCo ferromagnetic layer 22 and the FeCo layer adjacent the nonmagnetic layer 22′ are ferromagnetically coupled via the NiFe soft magnetic layer 24. Meanwhile, the FeCo layers adjacent the nonmagnetic layer 22′ on top and beneath the nonmagnetic layer 26 are antiferromagnetically coupled via the nonmagnetic layer 26. In
The main magnetic pole piece 2 according to an embodiment of the present invention was manufactured and evaluated in terms of film characteristics.
Reasons why there is a substantial decrease in the squareness S by inserting the NiFe soft magnetic layer 24 in the FeCo ferromagnetic layers 22 and making thinner the FeCo layer adjacent the nonmagnetic layer 22′ will be described below. Let JAF be exchange-coupling energy in antiferromagnetic coupling, then JAF may be expressed by the following equation:
J
AF
=Bs·t·Hs
(Bs: saturation magnetic flux density; t: magnetic layer film thickness; Hs: saturation magnetic field)
Assuming that JAF and Bs are constant, t is inversely proportional to Hs; specifically, the thinner the magnetic layer film thickness the greater the saturation magnetic field Hs, so that the antiferromagnetic coupling becomes strong to decrease the squareness S. Let us consider a model shown in
Reasons for the decreased squareness S will be described below. As the FeCo layer becomes thicker, crystal grains grow to increase roughness at an interface. If the FeCo layer adjacent Cr is thick, crystal grains of the FeCo layer adjacent Cr are large with the resultant greater roughness at the interface. In this case, a magnetic charge generated at the interface becomes great, so that magnetostatic coupling ferromagnetically coupling the FeCo layer adjacent Cr becomes great. This is considered to be the reason for an increased squareness S. If the NiFe intermediate layer is inserted in the FeCo layer, it is considered that the FeCo crystal grain growth is reset and started from a flat NiFe intermediate layer surface. If the FeCo layer adjacent Cr is thin, therefore, the FeCo crystal grains do not grow much. The crystal grains are small with the resultant small interface roughness. In this case, the magnetic charge generated at the interface becomes small, so that the magnetostatic coupling ferromagnetically coupling the FeCo layer adjacent Cr becomes small. This is considered to be the reason for the decreased squareness S.
As described heretofore, embodiments of the present invention can provide a main magnetic pole structure that ensures a markedly smaller squareness S (smaller remanent magnetization Mr) than the known art structure without inviting a reduced current response characteristic of the head or a degraded overwrite characteristic, though there is only a slight increase in the saturation magnetic field Hs. Embodiments of the invention can therefore provide a perpendicular magnetic recording head suppressing erasure after recording and suitable for high recording densities.
The embodiments of the present invention described heretofore provide the main magnetic pole piece 2 that has a structure including the multilayered films stacked one on top of another via the NiCr intermediate nonmagnetic layer 28, each multilayered film having the nonmagnetic layer 26 including one or a plurality of elements selected from the group consisting of Cr, Ru, Rh, and Ir, the FeCo ferromagnetic layers 22 disposed above and below the nonmagnetic layer 26, and the NiFe soft magnetic layers 24 inserted in the FeCo ferromagnetic layers 22 on the sides of the nonmagnetic layer 26 with respect to the center in the layer thickness direction of each FeCo ferromagnetic layer 22. The multilayered film may, instead, be single, even in which case, the same effect can be achieved as that of the above-described embodiment of the present invention. Specifically, the above effect can be achieved by the NiFe soft magnetic layers 24 being inserted in the FeCo ferromagnetic layers 22 on the sides of the nonmagnetic layer 26 with respect to the center in the layer thickness direction of each FeCo ferromagnetic layer 22.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-218566 | Aug 2007 | JP | national |
