Aspects of the present disclosure generally relate to magnetic recording heads of magnetic recording devices. A read head includes a first reader, an insulating separation layer, and a second reader disposed above the insulating separation layer. The second reader includes a magnetic seed layer and a cap layer. The second reader includes a first upper free layer disposed between the magnetic seed layer and the cap layer, and a second upper free layer disposed between the first upper free layer and the cap layer. The second reader includes a barrier layer. In one implementation the second reader includes an antiferromagnetic (AFM) layer disposed between the magnetic seed layer and the insulating separation layer to pin the magnetic seed layer.

An apparatus that includes a read sensor having a bearing surface and first and second free layers that are separated by an intermediate structure. The first FL includes multiple segments, with each segment having a width at the bearing surface. A sum of the widths of different ones of the multiple segments is a first width of the first FL. The second FL is unsegmented and has a second width at the bearing surface that is different from the first width of the first FL. The read sensor also includes a first terminal connected to a first one of the multiple segments of the first FL, and a second terminal connected to a second one of the multiple segments of the first FL. A third terminal is connected to the second FL. Control circuitry applies a bias current from either the first or second terminal to the third terminal.

Implementations described and claimed herein include a reader structure, comprising a first reader, including a sensor stack and a top shield structure, the top shield structure comprises a synthetic antiferromagnetic shield (SAF) structure, including a reference layer including at least a layer of NiFe and an impurity additive, an RKKY coupling layer RKKY coupling layer (e.g., Ru layer), and a pinned layer. In another implementation, the RL of the SAF shield structure of a first reader includes at least a layer of amorphous magnetic material. Yet, in another implementation, the SAF shield structure includes an insertion layer of amorphous magnetic material under the SAF shield RL, within the SAF shield RL or between the SAF shield RL and SAF shield Ru.

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.

An apparatus, according to one embodiment, includes a first circuit electrically coupled to a first read transducer and a first parallel circuit, the first read transducer having a tunnel valve structure having a resistance. A second circuit is electrically coupled to a second read transducer having a tunnel valve structure. An area of a tunnel barrier portion of the second read transducer along a plane of deposition thereof is larger than an area of a tunnel barrier portion of the first read transducer along a plane of deposition thereof.

An apparatus, according to one embodiment, includes: a plurality of tunnel valve read transducers arranged in an array extending along a read module. Each of the tunnel valve read transducers includes: a sensor structure having a cap layer, a free layer, a tunnel barrier layer, a reference layer and an antiferromagnetic layer, and electrically insulating layers on opposite sides of the sensor structure. Moreover, a height of the free layer measured in a direction perpendicular to a media bearing surface of the read module is less than a width of the free layer measured in a cross-track direction perpendicular to an intended direction of media travel.

An apparatus, according to one embodiment, includes a first circuit electrically coupled to a first read transducer and a first parallel circuit, the first read transducer having a tunnel valve structure having a resistance. A second circuit is electrically coupled to a second read transducer having a tunnel valve structure. An area of a tunnel barrier portion of the second read transducer along a plane of deposition thereof is larger than an area of a tunnel barrier portion of the first read transducer along a plane of deposition thereof.

An apparatus, according to one embodiment, includes a first circuit comprising a pair of terminals coupled to a first read transducer having a tunnel valve structure and a first parallel circuit. A second circuit has a pair of terminals that are coupled to a second read transducer having a tunnel valve structure. An area of a tunnel barrier portion of the second read transducer is larger than an area of a tunnel barrier portion of the first read transducer. The terminal resistance of the first circuit is less than about five times a terminal resistance of the second circuit.

A computer program product, system, and method are provided for direct resistance measurement of a magnetoresistive (MR) head of a storage drive in a storage system. In one embodiment, a voltage difference across the MR reader head is measured directly by applying an AC current to the MR head to generate an AC voltage across the MR head that can propagate through filter capacitors and be measured. In one embodiment, the voltage difference is amplified and the peak-to-peak voltage at the output of the amplifier is captured. Similarly, a reference voltage difference across a reference resistance is measured directly by applying a reference AC current to a reference resistance. The resistance of an MR reader head may be calculated directly as a function of the respective voltage differences without including the resistance of any bias resistors biasing the MR head.

An apparatus according to one embodiment includes a first read transducer having a tunnel valve structure, and a second read transducer coupled to the first read transducer. The second read transducer has a tunnel valve structure as well, but the tunnel valve structure of the first read transducer has a different resistivity than the tunnel valve structure of the second read transducer. An apparatus according to another embodiment includes an array of first read transducers, each first read transducer having a tunnel valve structure. At least a second read transducer is coupled to the first read transducers, the second read transducer having a tunnel valve structure. The tunnel valve structure of the first read transducer has a different resistivity than the tunnel valve structure of the second read transducer.