An apparatus according to one embodiment includes a magnetic head having at least two tunneling magnetoresistance sensors, where a resistance of a tunnel barrier of each of the tunneling magnetoresistance sensors of the magnetic head is about 25 ohms or less, a drive mechanism for passing a magnetic medium over the magnetic head, and a controller electrically coupled to the magnetic head. In addition, the controller includes a biasing circuit, where the biasing circuit restricts a maximum voltage drop across the tunnel barrier.

Reader-to-reader separation (RRS) is substantially decreased, and cross-track alignment of top and bottom sensors is improved with a process where a sidewall on the two sensors is formed during a single photolithography and ion beam etch sequence. RRS is minimized since the two sensors share a common reference layer (RL), and shields between the readers are omitted. A RL front portion is formed on a first stack of layers with a first free layer and uppermost first tunnel barrier, and a RL back portion is on a second stack comprising a reference layer and antiferromagnetic coupling layer sequentially formed on an antiferromagnetic layer. The RL may be a single layer or a synthetic antiferromagnetic structure so that the sensors operate in a common mode or differential mode, respectively. A third stack with a bottom second tunnel barrier and overlying second free layer is formed on the RL front portion.

A hard magnet stabilization scheme is disclosed for a top shield and junction shields for double or triple dimension magnetic reader structures. In one design, the hard magnet (HM) adjoins a top or bottom surface of all or part of a shield domain such that the HM is recessed from the air bearing surface to satisfy reader-to-reader spacing requirements and stabilizes a closed loop magnetization in the top shield. The HM may have a height and width greater than that of the top shield. The top shield may have a ring shape with a HM formed above, below, or within the ring shape, and wherein the HM stabilizes a vortex magnetization. HM magnetization is set or reset from room temperature to 100 C. to maintain a desired magnetization direction in the top shield, junction shield, and free layer in the sensor.

A bottom shield in a read head is modified by including a non-magnetic decoupling layer and second magnetic layer on a conventional first magnetic layer. The second magnetic layer has a magnetization that is not exchange coupled to the first magnetic layer, and a domain structure that is not directly affected by stray fields due to domain wall motion in the first magnetic layer. Accordingly, the modified bottom shield reduces shield related noise on the reader and will provide improved signal to noise (SNR) ratio and better reader stability. The second magnetic layer may be further stabilized with one or both of an antiferromagnetic coupling scheme, and insertion of an antiferromagnetic pinning layer. In dual readers, the modified bottom shield is used in either the bottom or top reader although in the latter, first magnetic layer thickness is reduced to maintain reader-to-reader spacing and acceptable bit error rate (BER).

A hard magnet stabilization scheme is disclosed for a top shield and junction shields for double or triple dimension magnetic reader structures. In one design, the hard magnet (HM) adjoins a top or bottom surface of all or part of a shield domain such that the HM is recessed from the air bearing surface to satisfy reader-to-reader spacing requirements and stabilizes a closed loop magnetization in the top shield. The HM may have a height and width greater than that of the top shield. The top shield may have a ring shape with a HM formed above, below, or within the ring shape, and wherein the HM stabilizes a vortex magnetization. HM magnetization is set or reset from room temperature to 100 C. to maintain a desired magnetization direction in the top shield, junction shield, and free layer in the sensor.

A hybrid dual reader. The hybrid dual reader includes first and second read sensors with conflicting design characteristics. The first read sensor includes at least one signal-to-noise ratio favoring design characteristic. The second read sensor includes at least one pulse width favoring design characteristic. The at least one signal-to-noise ratio favoring design characteristic is in conflict with the at least one pulse width favoring design characteristic.

An apparatus, according to one embodiment, includes: a module; and a plurality of tunnel valve read transducers arranged in an array extending along the module. Each of the tunnel valve read transducers includes: a sensor structure having a tunnel barrier layer and a free layer. Moreover, each of the tunnel valve read transducers includes a pair of hard bias magnets which sandwich the respective sensor structure therebetween, the hard bias magnets being positioned on opposite sides of the sensor structure along a cross-track direction. Furthermore, a thickness of each of the hard bias magnets at a thickest portion thereof is at least 10 times greater than a thickness of the free layer. Other systems, methods, and computer program products are described in additional embodiments.

A bottom shield in a read head is modified by including a non-magnetic decoupling layer and second magnetic layer on a conventional first magnetic layer. The second magnetic layer has a magnetization that is not exchange coupled to the first magnetic layer, and a domain structure that is not directly affected by stray fields due to domain wall motion in the first magnetic layer. Accordingly, the modified bottom shield reduces shield related noise on the reader and will provide improved signal to noise (SNR) ratio and better reader stability. The second magnetic layer may be further stabilized with one or both of an antiferromagnetic coupling scheme, and insertion of an antiferromagnetic pinning layer. In dual readers, the modified bottom shield is used in either the bottom or top reader although in the latter, first magnetic layer thickness is reduced to maintain reader-to-reader spacing and acceptable bit error rate (BER).

A bottom shield in a read head is modified by including a non-magnetic decoupling layer and second magnetic layer on a conventional first magnetic layer. The second magnetic layer has a magnetization that is not exchange coupled to the first magnetic layer, and a domain structure that is not directly affected by stray fields due to domain wall motion in the first magnetic layer. Accordingly, the modified bottom shield reduces shield related noise on the reader and will provide improved signal to noise (SNR) ratio and better reader stability. The second magnetic layer may be further stabilized with one or both of an antiferromagnetic coupling scheme, and insertion of an antiferromagnetic pinning layer. In dual readers, the modified bottom shield is used in either the bottom or top reader although in the latter, first magnetic layer thickness is reduced to maintain reader-to-reader spacing and acceptable bit error rate (BER).

A multi-sensor reader includes first and second read sensors. The first read sensor includes a first sensor stack including a sensing layer having a magnetization that changes according to an external magnetic field, and a first biasing component configured to magnetically bias the sensing layer of the first sensor stack in a first direction. The second read sensor includes a second sensor stack including a sensing layer having a magnetization that changes according to an external magnetic field, and a second biasing component configured to magnetically bias the sensing layer of the second sensor stack in a second direction that is substantially opposite the first direction.