Manipulation of Magnetic Properties and Magnetoresistance in Co/Cu/γ′-Fe4N/Mica Flexible Spin Valves via External Mechanical Strains

The strain-tailored magnetic and electronic transport properties in flexible spin valves (SPVs) have attracted attention due to their practical applications in flexible spintronic devices. Here, magnetic and spin-dependent electronic transport properties of Co/Cu/gamma'-Fe4N/mica flexible SPVs are investigated. The strain-induced change ratio of magnetoresistance (MR) is 49% in Co(4.8 nm)/Cu(7.5 nm)/gamma'-Fe4N(11.0 nm) flexible SPVs. The magnetic properties of Co(4.8 nm)/Cu(7.5 nm)/gamma'-Fe4N(7.9 nm) flexible SPVs show mechanical stability at bending strains. The magnetic properties of flexible SPVs did not deteriorate after 100 times of bending and 60 h of bending. As the Co layer thickness decreases from 7.2 to 2.4 nm, the sign of MR changes from negative to positive. A negative MR appears due to the opposite scattering spin asymmetry coefficients between Co/Cu and gamma'-Fe4N/Cu interfaces. A positive MR arises from the same scattering spin asymmetry coefficients at Co/Cu and gamma'-Fe4N/Cu interfaces or magnetization misalignments between Co and gamma'-Fe4N layers. Additionally, the MR is a combination of an anisotropy magnetoresistance and a giant magnetoresistance effect, which has been confirmed by MR-H curves with different measurement configurations (Hin-plane parallel to I, Hin-plane perpendicular to I and Hout-of-plane perpendicular to I) and M-H curves. The M-H curves show that the magnetization of gamma'-Fe4N reverses before that of the Co layer.

Automated summary

The strain-tailored magnetic and electronic transport properties of flexible spin valves were investigated. Different magnetoresistance effects were achieved by varying the thickness of the materials. The flexible spin valves showed good magnetic stability even after multiple bending.