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

Abstract

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/γ′-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)/γ′-Fe4N­(11.0 nm) flexible SPVs. The magnetic properties of Co­(4.8 nm)/Cu­(7.5 nm)/γ′-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 γ′-Fe4N/Cu interfaces. A positive MR arises from the same scattering spin asymmetry coefficients at Co/Cu and γ′-Fe4N/Cu interfaces or magnetization misalignments between Co and γ′-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 (H in‑plane∥I, H in‑plane⊥I and H out‑of‑plane⊥I) and M–H curves. The M–H curves show that the magnetization of γ′-Fe4N reverses before that of the Co layer.

Tunable Magnetic Domain Patterns in Thickness-Gradient Nickel Films on Flexible PDMS Substrates

“…Roughly, the stress regulations can be divided into two routes, one of which involves developing magnetic functional devices that are stable in a large deformation range by suppressing the stress effects. For example, the researchers have prepared flexible magnetic sensors and spin valve devices with high magnetic field sensitivity by using spontaneous wrinkling or applying a pre-stretching technique. , On the other hand, the stress effects can be harnessed to improve the magnetic properties of flexible magnetic films. The high-frequency characteristics of magnetic films can be effectively controlled by applying bending or stretching , to the substrate.…”

“…For example, the researchers have prepared flexible magnetic sensors and spin valve devices with high magnetic field sensitivity by using spontaneous wrinkling 8 or applying a pre-stretching technique. 9 , 10 On the other hand, the stress effects can be harnessed to improve the magnetic properties of flexible magnetic films. The high-frequency characteristics of magnetic films can be effectively controlled by applying bending 11 or stretching 12 , 13 to the substrate.…”