A system (10) and methodology is provided for resetting a pin layer within a GMR/Spin-Valve head (40). The system includes a preamplifier (20) to at least one of read, write, and bias a GMR head (40) having a pin layer (44). A pin layer reset circuit (30) generates a programmable signal (56) to reset the pin layer (44), wherein the programmable signal is adjustable according to at least one of a signal magnitude, signal polarity, signal pulse duration, and signal duty cycle. The programmable signal can include a voltage and and/or current.

Embodiments of the invention provide a method for recording bursts on a disk and a related apparatus. In accordance with an embodiment of the invention, a method for recording bursts on a burst field of a servo sector of a disk comprises generating a first write current corresponding to burst data provided by a write channel circuit, and generating a second write current having a higher frequency than the first write current using a high frequency AC current generator, wherein the high frequency AC current generator is independent from the write channel circuit. The method further comprises selectively applying the first write current to a write head in response to a signal and selectively applying the second write current to the write head in response to the signal.

Embodiments of the invention provide a method for recording bursts on a disk and a related apparatus. In accordance with an embodiment of the invention, a method for recording bursts on a burst field of a servo sector of a disk comprises generating a first write current corresponding to burst data provided by a write channel circuit, and generating a second write current having a higher frequency than the first write current using a high frequency AC current generator, wherein the high frequency AC current generator is independent from the write channel circuit. The method further comprises selectively applying the first write current to a write head in response to a signal and selectively applying the second write current to the write head in response to the signal.

The thin-film magnetic head has one (3) of thin-film magnetic cores (2,3) stacked on a substrate (1) and formed of two magnetic films (6,7) and a non-magnetic film (8) held between them with a current flowing through the thin-film magnetic core in the direction of hard axis thereof. The magnetoresistance effect magnetic head has one of a pair of shield cores (14,15) having a magnetoresistive element (13) between them formed of two magnetic films (14a,14b) and a non-magnetic film (14c) held between them the magnetoresistive element (13) being electrically connected (17a,17b) to the shield core, with a sense current flowing through the shield core. The current flowing through the one shield core via the magnetoresistive element is preferably an AC of decrement amplitude for demagnetizing the shield core along with a DC sense current. Also, this current preferably flows in the direction of hard axis of the shield core so that magnetic properties of the shield core are stabilized or demagnetized by the magnetic field generated in the direction of easy axis. The MR inductive head has a second thin-film magnetic core as a common magnetic body of an MR head and an inductive head on one substrate, formed of two magnetic films and a non-magnetic film held between them with a currect flowing through the second thin-film magnetic core in the direction of hard axis thereof.

A method and apparatus is disclosed for adaptively controlling the biasing current applied to magnetoresistive (MR) read heads (10a,10b,10c,10d) within a magnetic disk drive to provide optimized bias for each head/disk/channel component combination. An optimized bias current for each head is ascertained and stored on the disk surface at the time of manufacture. During each power up operation the values are transferred to random access memory which is accessed during the execution of each head switch command to apply bias current in accordance with the optimized value to the active MR head. Periodic reoptimization and updating of the stored values is effected by general error measurement circuitry (GEM) that forms a part of the device control system and is invoked to perform the reoptimization upon the occurrence of an event such as a predetermined duration of power on operation subsequent to the last reoptimization procedure.

A method and apparatus is disclosed for adaptively controlling the biasing current applied to magnetoresistive (MR) read heads (10a,10b,10c,10d) within a magnetic disk drive to provide optimized bias for each head/disk/channel component combination. An optimized bias current for each head is ascertained and stored on the disk surface at the time of manufacture. During each power up operation the values are transferred to random access memory which is accessed during the execution of each head switch command to apply bias current in accordance with the optimized value to the active MR head. Periodic reoptimization and updating of the stored values is effected by general error measurement circuitry (GEM) that forms a part of the device control system and is invoked to perform the reoptimization upon the occurrence of an event such as a predetermined duration of power on operation subsequent to the last reoptimization procedure.

The system includes a current- tapering circuit (100,105,112) which gradually reduces the WRITE (IW) current in a magnetic recording head (140) to zero over a time interval on the same order of magnitude as the characteristic relaxation time of the domain patterns in the magnetic recording head, rather than abruptly. Specific embodiments of the current-tapering circuit create a down-sloping ramp, a decaying exponential curve, and a high-frequency burst. The resultant magnetic recording system has reduced Barkhausen noise and reproducible READ performance as well as improved READ sensitivity following a WRITE operation.

The system includes a current- tapering circuit (100,105,112) which gradually reduces the WRITE (IW) current in a magnetic recording head (140) to zero over a time interval on the same order of magnitude as the characteristic relaxation time of the domain patterns in the magnetic recording head, rather than abruptly. Specific embodiments of the current-tapering circuit create a down-sloping ramp, a decaying exponential curve, and a high-frequency burst. The resultant magnetic recording system has reduced Barkhausen noise and reproducible READ performance as well as improved READ sensitivity following a WRITE operation.

Noise in the readback signal of a magnetic recording device resulting from spurious pulses in the readback signal produced by transitions of the magnetic remanent state of the yoke in the read/write transducer is eliminated by controlling the occurrence of the spurious pulses. Immediately following the completion of the write process, a decreasing amplitude alternating current (58) is applied to the read/write coil (49) of the transducer to drive the yoke remanent state to a stable or zero remanent state prior to the commencement of the read process.

A magnetic head utilizing the magnetoresistance effect comprises a magnetoresistance effect element (5) and a conductor (3) for applying a bias magnetic field to the element (5) by being supplied with a bias current (I_B). The conductor (3) is further supplied with a decaying alternating current superimposed on the bias current (I_B) in advance of the playback operation, so that the hysteresis effect on the magnetic circuit (9, 7, 8, 1) is cancelled and an invariable output characteristic is obtained for the magnetic head.