Abstract: Spin valve (SV) and magnetic tunnel junction (MTJ) magnetoresistive sensors are provided having magnetic layers with improved corrosion resistive properties. The SV and MTJ sensors include antiparallel (AP)-pinned layers formed of Co—Fe—X, where X is niobium (Nb), hafnium (Hf) or a mixture niobium and hafnium (NbHf) and laminated free layers formed of Co—Fe—X layers and Ni—Fe—Y layers, where Y is tantalum (Ta) or chromium (Cr). The addition of 5 to 10 atomic wt. % of Nb, Hf or NbHf to Co—Fe and 5 to 10 atomic wt. % Ta or Cr to Ni—Fe improves corrosion resistance by a self-passivation effect of the these metals. Addition of these metals to the magnetic layers reduces grain size of the layers resulting in increased electrical resistance leading to reduced sense current shunting and increased deltaR/R.

Abstract: Method and apparatus to correct an error of read-out data from a data storage medium, particularly a bit shift error, is described. The correction apparatus includes a gray bit detection circuit which flags bits with a phase shift exceeding a threshold and determines whether the previous or next bit cell has a smaller phase error. An RLL error detection circuit and a table containing valid bit combinations may be used in combination with the gray bit detector to correct errors on-the-fly without degrading performance. An advantage of the invention is that it allows correction of errors without regard to conventional ECC and its maximum number of errors.

Abstract: A spin valve (SV) magnetoresistive sensor is provided having an AP-pinned layer, an AP-coupled free layer and a non-magnetic electrically conductive spacer layer sandwiched between the AP-pinned layer and the free layer. The AP-pinned layer comprises first and second ferromagnetic layers separated by an antiparallel coupling (APC) layer. The AP-coupled free layer comprises a third ferromagnetic layer of Co—Fe adjacent to the spacer layer, a fourth ferromagnetic layer of Co—Fe—Hf—O and an APC layer sandwiched between the third and fourth ferromagnetic layers. The easy axis of the Co—Fe third ferromagnetic layer has a transverse orientation while the easy axis of the Co—Fe—Hf—O fourth ferromagnetic layer has a longitudinal orientation due to its higher thermal stability resulting in a low net intrinsic uniaxial anisotropy Hk for the AP-coupled free layer.

Abstract: An SV sensor with the preferred structure Substrate/Seed/Free/Spacer/Pinned/AFM/Cap where the seed layer is a non-magnetic Ni—Fe—Cr or Ni—Cr film and the AFM layer is preferably Ni—Mn. The non-magnetic Ni—Fe—Cr seed layer results in improved grain structure in the deposited layers enhancing the GMR coefficients and the thermal stability of the SV sensors. The improved thermal stability enables use of Ni—Mn with its high blocking temperature and strong pinning field as the AFM layer material without SV sensor performance degradation from the high temperature anneal step needed to develop the desired exchange coupling.

Abstract: The present invention provides, at a lower cost, a highly reliable data reading method and data reading apparatus that can improve backward sequential reading performance. The disk drive is provided with a magnetic disk and a control section having an HDC, a RAM, an MPU controlling the operation of the entire HDD, including control of the HDC, a ROM, and an I/F for connecting to an external host device. The control section executes a backward reading detection step that detects backward reading, a step of receiving a command that reads a block of a first length from a first LBA, a step that reads a block of the first length from the first LBA when backward reading is detected, and a step that pre-fetches a second block from a second LBA smaller than the first LBA; when backward reading is detected, upon completion of the reading of data from the disk, the reading of data predicted to be requested by the next command begins immediately.

Abstract: A method, devices, and an article of manufacture for reducing magnetic instability in a magnetoresistive read head of a combined read-write head after writing data onto a magnetic storage medium. The last write pulse polarity that results in the least amount of magnetic instability in the read head is determined, and is referred to as the designated polarity. Then, after a set of write pulses is written, it is determined whether the last write pulse has the designated polarity. If the last write pulse does not have the designated polarity, then an additional write pulse with the designated polarity is written. Thus, the last write pulse before a read always has the designated polarity, thereby reducing the magnetic instability of the read head, and consequently improving read head performance.

Abstract: A spin valve transistor sensor is provided having a emitter element, a collector element and a common base element. The negatively biased emitter element injects a spin polarized hot electron current into the base element by tunneling from a ferromagnetic pinned layer to a ferromagnetic free layer through a first tunnel barrier layer. The positively biased collector element, comprising a second tunnel barrier layer and a nonmagnetic metal layer, collects the fraction of the hot electron current that passes through the base element and over the barrier height of the second tunnel barrier layer. The hot electron current is strongly spin polarized and due to the GMR effect in the magnetic tunnel junction element, the magnitude of the base-collector current is strongly dependent on external magnetic (signal) fields. A process is provided for fabrication of a spin valve transistor sensor suitable for high density magnetic recording applications.

Abstract: A dual hybrid magnetic tunnel junction (MTJ)/giant magnetoresistance (GMR) sensor is provided having an MTJ stack, a GMR stack and a common free layer. The MTJ stack includes a first antiferromagnetic (AFM) layer, an first antiparallel (AP)-pinned layer and a tunnel barrier layer. The GMR stack, operating in the current perpendicular to the plane (CPP) mode, includes a second AFM layer, a second AP-pinned layer and a spacer layer. The first and second AFM layers are set to pin the magnetizations of the first and second AP-pinned layers perpendicular to the ABS and in the same direction with respect to each other resulting in an additive response to a signal field of the MTJ and GMR stacks. The thickness of the spacer layer in the GMR stack is chosen to provide a negative ferromagnetic coupling field between the second AP-pinned layer and the free layer which opposes the positive ferromagnetic coupling field between the first AP-pinned layer and the free layer across the tunnel barrier layer.

Abstract: A spin valve (SV) magnetoresistive sensor is provided having an AP-pinned layer, a laminated ferromagnetic free layer and a non-magnetic electrically conductive spacer layer sandwiched between the AP-pinned layer and the free layer. The AP-pinned layer comprises first and second ferromagnetic layers separated by an antiparallel coupling (APC) layer. The laminated free layer comprises a third ferromagnetic layer of Co—Fe adjacent to the spacer layer and a fourth ferromagnetic layer of Co—Fe—Hf—O. The Co—Fe—Hf—O material of the fourth ferromagnetic layer has high resistivity resulting in reduced sense current shunting by the free layer. In addition, the metal oxide material of the fourth ferromagnetic layer is known to cause specular scattering of electrons. The reduced sense current shunting and the specular scattering of electrons both contribute to improving the GMR coefficient of the SV sensor.

Abstract: A trilayer seed layer structure is employed between a first read gap layer and a spin valve sensor for improving the magnetic and giant magnetoresistive properties and the thermal stability. In the spin valve sensor, the trilayer seed layer structure is located between a first read gap layer and a ferromagnetic free layer. The antiferromagnetic pinning layer is preferably nickel manganese (Ni—Mn). The trilayer seed layer structure includes a first seed layer that is a first metallic oxide, a second seed layer that is a second metallic oxide and a third seed layer that is a nonmagnetic metal. A preferred embodiment is a first seed layer of nickel oxide (NiO), a second seed layer of nickel manganese oxide (NiMnOx), and a third seed layer of copper (Cu).

Abstract: A differential magnetic tunnel junction (MTJ) sensor is provided having a first MTJ stack, a second MTJ stack and a common AP-coupled free layer. The AP-coupled free layer comprises a ferromagnetic first sense layer and a ferromagnetic second sense layer with an antiferromagnetic coupling (APC) layer disposed between the two sense layers providing strong antiferromagnetic coupling. The thickness of the first sense layer is chosen to be different (greater or smaller) than the thickness of the second sense layer so that the AP-coupled free layer has a net magnetic moment oriented parallel to the ABS and free to rotate in the presence of a signal magnetic field. Antiferromagnetic (AFM) layers in the first and second MTJ stacks are set to pin the magnetizations of pinned layers in each stack perpendicular to the ABS and in the same direction with respect to one another.

Abstract: The present invention provides, at a lower cost, a highly reliable data reading method and data reading apparatus that can improve backward sequential reading performance. The disk drive is provided with a magnetic disk and a control section having an HDC, a RAM, an MPU controlling the operation of the entire HDD, including control of the HDC, a ROM, and an I/F for connecting to an external host device. The control section executes a backward reading detection step that detects backward reading, a step of receiving a command that reads a block of a first length from a first LBA, a step that reads a block of the first length from the first LBA when backward reading is detected, and a step that pre-fetches a second block from a second LBA smaller than the first LBA; when backward reading is detected, upon completion of the reading of data from the disk, the reading of data predicted to be requested by the next command begins immediately.

Abstract: An ion beam sputtering system having a chamber, an ion beam source, multiple targets, a shutter, and a substrate stage for securely holding a wafer substrate during the ion beam sputtered deposition process in the chamber. The substrate stage is made to tilt about its vertical axis such that the flux from the targets hit the wafer substrate at a non-normal angle resulting in improved physical, electrical and magnetic properties as well as the thickness uniformity of the thin films deposited on the substrate in the ion beam sputtering system.

Abstract: A soft anti-parallel (AP)-pinned spin valve (SV) sensor comprising an AP-pinned layer separated from a ferromagnetic free layer by a non-magnetic electrically conducting spacer. The AP-pinned layer includes a first ferromagnetic pinned layer separated from a second ferromagnetic pinned layer by an anti-parallel coupling layer. The second pinned layer further includes a first and second ferromagnetic sub-layers. The first pinned layer which is the farthest pinned layer from the free layer is made of soft (low coercivity) magnetic material. The use of a low coercivity first pinned layer allows the magnetic field generated by the sense current to be used in setting the magnetizations directions of the pinned layer and reset the magnetization direction during the disk operation in the case that the magnetization direction becomes random.

Abstract: An antiparallel (AP)-pinned spin valve (SV) sensor is provided which has positive and negative read signal symmetry about a zero bias point of a transfer curve upon sensing positive and negative magnetic incursions of equal magnitude from a moving magnetic medium. The SV sensor includes a ferromagnetic free layer which has a magnetic moment which is free to rotate in first and second directions from a position which corresponds to the zero bias point upon sensing positive and negative magnetic incursions, respectively, an AP-pinned layer, an antiferromagnetic layer which pins the magnetic moment of the AP-pinned layer along a pinned direction, and a spacer layer sandwiched between the AP-pinned layer and the free layer.

Abstract: A magnetic tunnel junction (MTJ) device for use as a magnetic field sensor in a magnetic disk drive or as a memory cell in a magnetic random access (MRAM) array has an antiferromagnetic (AFM) layer formed of electrically insulating antiferromagnetic material. The magnetic tunnel junction in the sensor is formed on a first shield, which also serves as an electrical lead, and is made up of a stack of layers forming an MTJ sensor stripe. The layers in the stack are an AFM layer, a pinned ferromagnetic layer exchange biased with the AFM layer so that its magnetic moment cannot rotate in the presence of an applied magnetic field, a free ferromagnetic layer whose magnetic moment is free to rotate in the presence of an applied magnetic field, and an insulating tunnel barrier layer disposed between the pinned layer and the free layer. The MTJ sensor stripe is generally rectangularly shaped with parallel side edges and a back edge and a front edge at the air bearing surface (ABS).

Abstract: A disk drive system having a magnetic tunnel junction (MTJ) sensor having two MTJ stacks between first and second shields and a common electrode disposed between the two MTJ stacks. A first sense current is provided to the first MTJ stack by the first shield and the common electrode and a second sense current is provided to the second MTJ stack by the second shield and the common electrode. The magnetization directions of the pinned layers of the first and second MTJ stacks are fixed perpendicular to the ABS and antiparallel with respect to each other so that the magnetoresistive signal generated due to an external field from a disk by the first MTJ stack differs in phase by 180° with respect to the magnetoresistive signal generated due to the same external field by the second MTJ stack.

Abstract: A fully-pinned, flux-closed spin valve (SV) magnetoresistive sensor having a reference (pinned) layer with magnetization fixed by a first antiferromagnetic (AFM1) layer, and a keeper layer with magnetization fixed by a second antiferromagnetic (AFM2) layer. The magnetization of the keeper layer is saturated and fixed in an antiparallel orientation to the pinned layer magnetization by an exchange interaction with the AFM2 layer. The magnetic moments of the pinned layer and the keeper layer are approximately matched to form a flux-closed magnetic configuration wherein demagnetizing fields in the pinned layer are largely canceled and magnetostatic interaction with the free layer is reduced. Saturation of the keeper layer magnetization by exchange coupling with the AFM2 layer eliminates or reduces magnetization canting at the edges of the keeper layer which can result in signal field shunting through the keeper layer.

Abstract: An SV sensor with the preferred structure Substrate/Seed/Free/Spacer/Pinned/AFM/Cap where the seed and cap layers are formed of a non-magnetic, electrically insulating oxide, NiMnOx. The non-magnetic electrically insulating NiMnOx seed layer results in enhanced GMR coefficient and improved thermal stability of the SV sensor. The improved thermal stability enables use of Ni—Mn with its high blocking temperature and strong pinning field as the AFM layer material, as well as other Mn alloys, without SV sensor performance degradation from the high temperature anneal step needed to develop the desired exchange coupling. The electrically insulating property of the NiMnOx seed and cap layer material decreases sense current shunting and further reduces shield/sensor shorting.

Abstract: An SV sensor with the preferred structure Substrate/Seed/Free/Spacer/Pinned/AFM/Cap where the seed layer is a non-magnetic Ni--Fe--Cr or Ni--Cr film and the AFM layer is preferably Ni--Mn. The non-magnetic Ni--Fe--Cr seed layer results in improved grain structure in the deposited layers enhancing the GMR coefficients and the thermal stability of the SV sensors. The improved thermal stability enables use of Ni--Mn with its high blocking temperature and strong pinning field as the AFM layer material without SV sensor performance degradation from the high temperature anneal step needed to develop the desired exchange coupling.