Reversal of the Pinning Direction in the Synthetic Spin Valve with a NiFeCr Seed Layer.

The effect of the seed layers on the magnetic properties of the giant magnetoresistance thin films has received a lot of attention. Here, a synthetic spin valve film stack with a wedge-shaped NiFeCr seed layer is deposited and annealed following a zero-field cooling procedure. The film crystallinity and magnetic properties are studied as a function of the NiFeCr seed layer thickness. It is found that the exchange coupling field from the IrMn/CoFe interface and the antiferromagnetic coupling field in the synthetic antiferromagnet both increase as the seed layer thickness increases, indicating the perfection of film texture. In this film, the critical thickness of the NiFeCr seed layer for the formation of the ordered IrMn3 texture is about 9.3 nm. Meanwhile, a reversal of the pinning direction in the film is observed at this critical thickness of NiFeCr. This phenomenon can be explained in a free energy model by the competition effect between the exchange coupling and the interlayer coupling during the annealing process.

Magnetoresistive sensors based on the elasticity of domain walls.

Magnetic sensors based on magnetoresistance effects have promising application prospects due to their excellent sensitivity and their advantages in terms of integration. However, the competition between higher sensitivity and a larger measuring range remains a problem. Here, we propose a novel mechanism for designing magnetoresistive sensors: probing the perpendicular field by detecting the expansion of the elastic magnetic domain wall in the free layer of a spin valve or a magnetic tunnel junction. The performances of devices based on this mechanism, such as the sensitivity and the measuring range, can be tuned by manipulating the geometry of the device. This can be achieved without changing the intrinsic properties of the material, thus promising a higher integration level and a better performance. The mechanism is theoretically explained based on the experimental results. Two examples are proposed and their functionality and performances are verified via a micromagnetic simulation.

Design and Fabrication of Full Wheatstone-Bridge-Based Angular GMR Sensors.

Since the discovery of the giant magnetoresistive (GMR) effect, GMR sensors have gained much attention in last decades due to their high sensitivity, small size, and low cost. The full Wheatstone-bridge-based GMR sensor is most useful in terms of the application point of view. However, its manufacturing process is usually complex. In this paper, we present an efficient and concise approach to fabricate a full Wheatstone-bridge-based angular GMR sensor by depositing one GMR film stack, utilizing simple patterned processes, and a concise post-annealing procedure based on a special layout. The angular GMR sensor is of good linear performance and achieves a sensitivity of 0.112 mV/V/Oe at the annealing temperature of 260 °C in the magnetic field range from -50 to +50 Oe. This work provides a design and method for GMR-sensor manufacturing that is easy for implementation and suitable for mass production.