Magnetization processes in spin-valve meanders for sensor applications

Abstract

We used Kerr microscopy to investigate the magnetization processes of NiFe-Co/Cu/Co/ FeMn spin-valve meanders for magnetoresistive sensors and compared them to processes in related single films and bilayers. We observed irregular switching, characterized by the irreversible decay of blocked domains or by domain nucleation at 360 walls, in the related films and in the free layer of the spin-valve system. Both effects are connected with hysteresis. Edge-curling walls are responsible for rotational hysteresis in the giant magnetoresistance signal of the spin valves, occurring during field rotation in clockwise and counterclockwise directions. The U-turns of the meanders and their shape have no relevant influence on the magnetization behavior and hysteresis effects.

Concentric 360° domain wall nesting in magnetic tunnel junction films: a Lorentz TEM study

“…In particular, the formation of 360° domain walls (DWs) has been reported for MTJ [9][10][11] and related exchange bias systems [12][13][14][15][16] and is known to disrupt uniform switching, leading to noise and stability issues during device operation. Conceptually, these 360° DWs arise from the coalescence of two of the more common 180° Néel DWs that separate regions of opposite magnetisation [17,18], often because the first 180° DW becomes pinned by a structural defect.…”

Uniaxial anisotropy variations and the reduction of free layer coercivity in MnIr-based top spin valves

“…Practical applications, however, need the micron-sized spin valves with the crossed magnetic anisotropy configuration. The authors of [7,8] studied the elements in the form of stripes where the form anisotropy becomes essential and results in the change in the shape of magnetoresistive curve. In [9,10], the spin valve in the form of meander was investigated and the free layer coercivity, GMR effect, and magnetoresistive sensitivity were found to depend on the meander bar width.…”