The study on magnetoresistance of ellipsoidal flexible spin-valve with various aspect ratios

Abstract

Flexibility in spintronic devices, such as spin-valve and spin-filter, would give lots of advantages for multifarious applications, such as magnetic biosensors, memory, and spin-logic. We fabricated an ellipse-shaped spin-valve with various aspect ratios on the flexible polypropylene film. Then, we investigate how repetitive mechanical bending changes the magnetic configuration and corresponding magnetoresistance of the spin valve depending on the shape. Permalloy, NiFe, which has a low magnetostriction coefficient value, was used for the pinned and free layers of the spin-valve. The compressive stress was applied to the spin-valve films by repetitive bending the films in a downward direction. It is found that the magnetic anisotropy and corresponding magnetoresistance are affected significantly by the bending stress and that the results can be interpreted successfully in terms of the inverse magnetostriction effect. In order to reduce the deterioration of the flexible spin-valve due to the bending stress, the aspect ratio of the ellipsoidal spin-valve was increased from 1 to 8. As a result, almost no change in the free layer coercivity was observed for the spin-valve with an aspect ratio of 8, even if the bending stress is increased. This indicates that the durability of the flexible spin-valve can be enhanced by adjusting the shape and the aspect ratio.