Coating processes – Coating by vapor – gas – or smoke – Plural coatings applied by vapor – gas – or smoke
Reexamination Certificate
2001-07-17
2003-04-15
Chen, Bret (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
Plural coatings applied by vapor, gas, or smoke
C427S250000, C427S294000, C427S309000, C360S324100
Reexamination Certificate
active
06548114
ABSTRACT:
The present invention relates to data storage systems. More specifically, the present invention relates to data storage systems using read heads which utilize the giant magnetoresistive (GMR) effect.
Magnetic sensors utilizing the GMR effect, frequently referred to as “spin valve” sensors, are known in the art. A spin valve 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. Magnetic pinning of the pinned layer is frequently accomplished using an adjacent antiferromagnetic layer, commonly referred to as the “pinning layer,” through exchange coupling. The pinned layer must be kept magnetically rigid at a device operating temperature of about 150° C. in a disc drive where an excitation field as high as 300 Oe is applied to the sensor. 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. Spin valve/GMR sensors provide an output which is dependent upon angle variation of the magnetizations between the free and pinned layers.
One type of self pinned layer is known in the art as an artificial antiferromagnetic layer (AAF) or a synthetic antiferromagnetic layer (SAF). Such a SAF layer is formed by three sub-layers, a first ferromagnetic layer, a second ferromagnetic layer and a non-magnetic spacer layer separating the two ferromagnetic layers. The two ferromagnetic layers have magnetic vectors which are biased in antiparallel directions and in the plane of the sensor (perpendicular to the air bearing surface). This is described in, for example, U.S. Pat. No. 5,583,725, issued Dec. 10, 1996 to Coffey et al., entitled “SPIN VALVE MAGNETORESISTIVE SENSOR WITH SELF-PINNED LAMINATED LAYER AND MAGNETIC RECORDING SYSTEM USING THE SENSOR, which is incorporated herein by reference.
An Ru/Co/Ru SAF layer has been used in combination with an NiO antiferromagnetic layer in a spin valve. See for example, R. E. Fontana, U.S. Pat. No. 5,701,223 entitled A SPIN VALVE MAGNETORESISTIVE SENSOR WITH ANTIPARALLEL PINNED LAYER AND IMPROVED EXCHANGE BIAS LAYER, AND MAGNETIC RECORDING SYSTEM USING THE SAME. An apparent purpose of combining the Ru/Co/Ru SAF layer with the NiO antiferromagnetic layer was to reduce the demag field from the pinned layer in order to optimize the bias point of the sensor. An additional benefit was the enhancement of the pinning/switching field. However, the thermal relaxation in a NiO spin valve is severe due to the low blocking temperature (approximately 200° C.) and poor blocking temperature distribution. This spin valve structure lacks stability, and is therefore not ideal for a read sensor.
FIG. 1
is a plot illustrating the temperature dependence of such a spin valve having an NiO antiferromagnetic layer and a SAF pinned layer. As can be seen in
FIG. 1
, this spin valve structure exhibits poor thermal stability. Further, the GMR transfer curves (plotting resistance of the sensor as a function of applied magnetic field) exhibit a permanent change after experiencing a thermal temperature ramp.
SUMMARY OF THE INVENTION
Disclosed are a spin valve magnetoresistive sensor and methods of fabricating the same. The sensor includes a free layer, a synthetic antiferromagnetic (SAF) layer, a spacer layer positioned between the free layer and the SAF layer, and a Mn-based antiferromagnetic pinning layer with a high blocking temperature in contact with the SAF layer. For example, a NiMn layer having a blocking temperature of approximately 400° C. or a PtMn layer having a blocking temperature of approximately 380° C. can be used. The SAF layer includes first and second ferromagnetic CoFe layers and an Ru spacer layer positioned between and directly in contact with the first and second CoFe ferromagnetic layers.
REFERENCES:
patent: 4949039 (1990-08-01), Grunberg
patent: 5206590 (1993-04-01), Dieny et al.
patent: 5475304 (1995-12-01), Prinz
patent: 5534355 (1996-07-01), Okuno et al.
patent: 5576915 (1996-11-01), Akiyama et al.
patent: 5583725 (1996-12-01), Coffey et al.
patent: 5616370 (1997-04-01), Okuno et al.
patent: 5650887 (1997-07-01), Dovek et al.
patent: 5686838 (1997-11-01), van den Berg
patent: 5688605 (1997-11-01), Iwasaki et al.
patent: 5696655 (1997-12-01), Kawano et al.
patent: 5696656 (1997-12-01), Gill et al.
patent: 5701223 (1997-12-01), Fontana, Jr. et al.
patent: 5702832 (1997-12-01), Iwasaki et al.
patent: 5705973 (1998-01-01), Yuan et al.
patent: 5717550 (1998-02-01), Nepela et al.
patent: 5725963 (1998-03-01), Iwasaki et al.
patent: 5738946 (1998-04-01), Iwasaki et al.
patent: 5739988 (1998-04-01), Gill
patent: 5739990 (1998-04-01), Ravipati et al.
patent: 5742162 (1998-04-01), Nepela et al.
patent: 5751521 (1998-05-01), Gill
patent: 5756191 (1998-05-01), Hashimoto et al.
patent: 5764056 (1998-06-01), Mao et al.
patent: 5768066 (1998-06-01), Akiyama et al.
patent: 5768069 (1998-06-01), Mauri
patent: 5869963 (1999-02-01), Saito et al.
patent: 5880913 (1999-03-01), Gill
patent: 5883764 (1999-03-01), Pinarbasi
patent: 5976713 (1999-11-01), Fuke et al.
patent: 6061210 (2000-05-01), Gill
patent: 6088195 (2000-07-01), Kamiguchi et al.
patent: 6094325 (2000-07-01), Tagawa et al.
patent: 6101072 (2000-08-01), Hayashi
patent: 6134090 (2000-10-01), Mao et al.
patent: 6191926 (2001-02-01), Everitt et al.
patent: 6306266 (2001-10-01), Metin et al.
patent: 6340533 (2002-01-01), Ueno et al.
patent: 6404606 (2002-06-01), Pinarbasi et al.
patent: 6433972 (2002-08-01), Mao et al.
“Linearity of Unshielded Spin-Valve Sensors”, by N. Sugaware et al., American Institute of Physics, Jan. 27, 1997, pp. 523-525.
“AMR Effect in Spin-Valve Structure”, by Y. Uehara et al., IEEE Transactions on Magnetics, vol. 32, No. 5, Sep. 1996, pp. 3432-3433.
“Thermal Fluctuation Aftereffect of Exchange Coupled Films for Spin Valve Devices”, by J. Fujikata, K. Hayashi, H. Yamamoto and M. Nakada, J. Appl. Phys., vol. 83, No. 11, Jun. 1, 1998, American Institute of Physics, pp. 7210-7212.
“NiMn-Pinned Spin Valves with High Pinning Field Made by Ion Beam Sputtering”, by S. Mao, S. Gangopadhyay, N. Amin and E. Murdock, Appl. Phys. Lett., vol. 69, No. 23, Dec. 2, 1996, American Institute of Physics, pp. 3593-3595.
“Temperature Dependence of Giant Magnetoresistance Properties of NiMn Pinned Spin Valves”, by S. Mao, N. Amin and E. Murdock, Appl. Phys., vol. 83, No. 11, Jun. 1, 1998, American Institute of Physics, pp. 6807-6809.
Everitt Brenda A.
Gao Zheng
Mack Anthony M.
Mao Sining
Murdock Edward S.
Chen Bret
Seagate Technology LLC
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