The invention relates generally to data storage systems and, more specifically, to data storage systems having read heads which employ magnetoresistive sensors.
As storage density increases, the magnetic field being sensed during read by a magnetoresistive sensor in a read head of a data storage system becomes smaller. Thus, there is an ongoing desire to provide improved sensitivity of reads.
One way to improve the performance of a read head is to replace conventional anisotropic magnetoresistive (AMR) sensors with giant magnetoresistive (GMR) sensors, as GMR sensors provide a greater response to a magnetic field in comparison to AMR sensors. The GMR or “spin valve” sensor is characterized by a magnetoresistive (MR) coefficient that is substantially higher than the MR coefficient of an AMR sensor. A GMR sensor is typically a sandwiched structure consisting of two ferromagnetic layers separated by a thin non-ferromagnetic layer. One of the ferromagnetic layers is called the “pinned layer” because it is magnetically pinned or oriented in a fixed and unchanging direction by an adjacent anti-ferromagnetic layer, commonly referred to as the “pinning layer,” through anti-ferromagnetic exchange coupling. The other ferromagnetic layer is called the “free” or “unpinned” layer because the magnetization is allowed to rotate in response to the presence of external magnetic fields. When a sense current is applied to the sensor in the presence of a magnetic field such as that provided by magnetic storage medium, the resistance of the GMR sensor changes resulting in a change in voltage due to the applied sense current. This voltage change may be measured and used to read back information. A GMR sensor fabricated from the appropriate materials provides improved sensitivity and greater change in resistance than observed in AMR sensors. Thus, GMR sensors have become the preferred type of magnetoresistive sensor for data storage systems such as magnetic disk and tape drives.
Certain materials in the GMR sensor that are exposed on the head surface (also known as the air bearing surface or “ABS” with respect to disk drive heads, and the tape bearing surface or “TBS” with respect to tape drive heads) are quite prone to corrosion, making heads which utilize GMR sensors extremely sensitive to corrosion in the environments in which they are expected to operate. Disk drive heads, which operate in an environment sealed at the factory in clean room conditions, are less susceptible to corrosion than tape drive heads, which must operate while exposed to an often quite harsh ambient atmosphere. Also, typically the ABS of the disk drive head is coated with a thin protective film, which is hard and wear resistant on the air bearing surface of a disk drive head. Unfortunately, the nature of tape recording makes the protective overcoat a poor solution for tape drive heads. Tape recording always involves contact between the tape and head, and the surface of the tape is more abrasive than that of a disk. Consequently, the protective film wears off in an unacceptable amount of time.
In one aspect of the invention, a magnetoresistive sensor in a tape drive read head having a tape bearing surface includes a magnetoresistive sensing element and a flux guide disposed on a surface of the magnetoresistive sensing element to form a portion of the tape bearing surface.
Embodiments of the invention may include one or more of the following features.
The magnetoresistive sensing element can be GMR element, or an AMR element.
The GMR element can include a spacer layer, an antiferromagnetic exchange layer and a pinned layer, and the flux guide can cover the surface of the GMR element to the extent that the flux guide prevents exposure of the spacer, antiferromagnetic exchange and pinned layers on the tape bearing surface.
The flux guide can be made of a permeable material, and the permeable material an be a nickel-iron alloy.
In another aspect of the invention, a tape drive head includes a write portion and a read portion, the read head portion including a magnetoresistive sensor having a tape bearing surface. The magnetoresistive sensor includes a magnetoresistive sensing element and a flux guide disposed on a surface of the magnetoresistive sensing element to form a portion of the tape bearing surface of the magnetoresistive sensor.
In yet another aspect of the invention, a tape drive includes a magnetic tape, a read head to read information recorded on the magnetic tape and a magnetoresistive sensor in the read head. The magnetoresistive sensor has a tape bearing surface, and includes a magnetoresistive sensing element and a flux guide disposed on a surface of the magnetoresistive sensing element to form a portion of the tape bearing surface of the magnetoresistive sensor.
In yet another aspect of the invention, a method of manufacturing a thin film read head includes providing a GMR film to a surface of a read gap insulating layer and processing the GMR film to produce a GMR sensing element having a flux guide disposed thereon, the flux guide forming a portion of a tape bearing surface of the thin film read head.
Particular implementations of the invention may provide one or more of the following advantages. The flux guide allows GMR sensors to be used in tape drive heads without the corrosion prone materials such as Cu, and to a lesser degree, CoFe and the AFM exhange materials, being exposed on the TBS. It also allows the GMR element stripe height to be defined by high precision photolithographic techniques as opposed to the less controllable mechanical lapping that is typically used in the manufacture of GMR sensors. The flux guide can be made of a high permeability material such as nickel iron (NiFe) flux, thus providing for the easy conduction of flux to the GMR sensors. In addition, because the flux guide is maintained in a single domain (i.e., there are no domain wall motions), flux can conduct more freely.
Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.
Referring to
The support 14 is mounted on a movable support 26, which moves transverse to the magnetic tape 16 so that the head 12 can read and write magnetic information signals on the longitudinally moving tape 16. The head 12 can read servo information on the tape so as to keep the head 12 within a desired track. The head 12 provides the servo information to a position controller 28, which processes the servo information and provides head movement signals to the movable support 26. Further, the head 12 is connected to a read/write controller 30, which processes data read from the tape by the head 12 and provides write data to the head 12 for recording on the tape 16.
The write head portion 40 includes a coil layer 54 sandwiched between first and second insulation layers 56 and 58. A third insulation layer 60 may be employed for planarizing the read/write head 12 to eliminate ripples in the second insulation layer 58 caused by the coil layer 54. The first, second and third insulation layers are referred to in the art as an “insulation stack”. The coil layer 54 and the first, second and third insulation layers 56, 58 and 60 are sandwiched between bottom and top pole piece layers 62 and 64. The bottom and top pole piece layers 62 and 64 are magnetically coupled at a back gap 66. The top pole piece layer 64 has a top pole tip 70, which is separated from the bottom pole piece layer 62 by a write gap layer 72 at the head tape bearing surface 18. Above the top pole piece layer 64 is an overcoat layer 76.
It will be appreciated that, while the illustrated embodiment is a merged head in which a single ferromagnetic layer functions as a second shield layer of the read head and as the first pole piece layer of the write head, the second shield layer and the first pole piece layer could be separate layers.
Referring to
A sensing current provided from a tape drive current source and carried in a current path through the conductor 84a and permanent magnet 82a flows in the plane of the GMR stack elements and exits the stack via a current path through the permanent magnet 82b and conductor 84b to produce operation in a current-in-the-plane (CIP) mode.
It should be understood that the spin valve may be either a top or a bottom type spin valve, as later illustrated in
Although the MR sensor 44 has been illustrated as a GMR sensor, it may be any one of a plurality of MR-type sensors, including, but not limited to, top or bottom spin valve GMR, AMR, SAF GMR and spin tunneling. Also, although the described embodiment is a GMR sensor utilizing a spin valve structure operating in a CIP mode, it will be understood that a spin valve GMR sensor operating in a current-perpendicular-to-the-plane (CPP) mode could be used.
Referring to
In the manufacture of conventional GMR sensors, the tape bearing surface of the GMR film is not etched but instead lapped to achieve a desired GMR element stripe height. It is critical to accurately control the size of the GMR element during the lapping process since the performance of a GMR sensor is dependent on the stripe height of its sensing element. Because mechanical lapping processes have substantial manufacturing tolerances associated with them, however, it is extremely difficult to accurately control the stripe height during the lapping process. In contrast, the process 114, through the use of an appropriately dimensioned photoresist, allows the stripe dimension to be controlled with greater precision than is possible with lapping processes.
Referring to
Referring to
Other embodiments are within the scope of the following claims.
Number | Name | Date | Kind |
---|---|---|---|
4130847 | Head et al. | Dec 1978 | A |
5210667 | Zammit | May 1993 | A |
5463805 | Mowry et al. | Nov 1995 | A |
5544774 | Gray | Aug 1996 | A |
5617273 | Carr et al. | Apr 1997 | A |
5666248 | Gill | Sep 1997 | A |
5710683 | Sundaram | Jan 1998 | A |
5772493 | Rottmayer et al. | Jun 1998 | A |
5896253 | Dirne et al. | Apr 1999 | A |
5991119 | Boutaghou et al. | Nov 1999 | A |
6193584 | Rudy et al. | Feb 2001 | B1 |
6205008 | Gijs et al. | Mar 2001 | B1 |
6219205 | Yuan et al. | Apr 2001 | B1 |
6266217 | Ruigrok et al. | Jul 2001 | B1 |
6275033 | Kools | Aug 2001 | B1 |
6347983 | Hao et al. | Feb 2002 | B1 |
6359754 | Riddering et al. | Mar 2002 | B1 |
6381106 | Pinarbasi | Apr 2002 | B1 |
6396670 | Murdock | May 2002 | B1 |
6433965 | Gopinathan et al. | Aug 2002 | B1 |
6438026 | Gillies et al. | Aug 2002 | B2 |
6669787 | Gillies et al. | Dec 2003 | B2 |
6678126 | Katakura et al. | Jan 2004 | B2 |
6765770 | Dee | Jul 2004 | B2 |
20010026470 | Gillies et al. | Oct 2001 | A1 |
20010040777 | Watanabe et al. | Nov 2001 | A1 |
20020012204 | Boutaghou et al. | Jan 2002 | A1 |
20020024880 | Mao et al. | Feb 2002 | A1 |
20020034661 | Gillies et al. | Mar 2002 | A1 |
20020053129 | Watanuki | May 2002 | A1 |
20020118493 | Kondo et al. | Aug 2002 | A1 |
20020191348 | Hasegawa et al. | Dec 2002 | A1 |
20030002230 | Dee et al. | Jan 2003 | A1 |
20030002232 | Dee | Jan 2003 | A1 |
20030072110 | Dee | Apr 2003 | A1 |
20030200041 | Church et al. | Oct 2003 | A1 |
20030206383 | Meguro et al. | Nov 2003 | A1 |
20040032696 | Johnson et al. | Feb 2004 | A1 |
Number | Date | Country |
---|---|---|
497403 | Aug 1992 | EP |
498492 | Aug 1992 | EP |
519558 | Dec 1992 | EP |
1 176 585 | Jan 2002 | EP |
1 376 543 | Jan 2004 | EP |
2169434 | Jul 1986 | GB |
62075924 | Apr 1987 | JP |
05266425 | Oct 1993 | JP |
07153036 | Jun 1995 | JP |
07230610 | Aug 1995 | JP |
08153310 | Jun 1996 | JP |
11-120523 | Apr 1999 | JP |
2001291214 | Oct 2001 | JP |
Number | Date | Country | |
---|---|---|---|
20030235015 A1 | Dec 2003 | US |