Bending Strain-Tailored Magnetic and Electronic Transport Properties of Reactively Sputtered γ′-Fe4N/Muscovite Epitaxial Heterostructures toward Flexible Spintronics

The strain modulation on the magnetic and electronic transport properties of the ferromagnetic films is one of the hot topics due to the practical applications in flexible and wearable spintronic devices. However, the large strain-induced saturation magnetization and resistance change is not easy to achieve because most of the ferromagnetic films deposited on flexible substrates are polycrystalline or amorphous. Here, the flexible epitaxial gamma'-Fe4N/mica films are fabricated by facing-target reactive sputtering. At a tensile strain with a radius of curvature (ROC) of 3 mm, the saturation magnetization (M-s) of the gamma'-Fe4N/mica film is tailored significantly with a maximal variation of 210%. Meanwhile, the magnetic anisotropy was broadly tunable at different strains, where the out-of-plane M-r/M-s at a tensile strain of ROC = 2 mm is six times larger than that at the unbent state. Besides, the strain-tailored longitudinal resistance R-xx and anomalous Hall resistivity rho(xy) appear where the drop of R-xx (rho(xy)) reaches 5% (22%) at a tensile strain of ROC = 3 mm. The shift of the nitrogen position in the gamma'-Fe4N unit cell at different bending strains plays a key role in the strain-tailored magnetic and electronic transport properties. The flexible epitaxial gamma'-Fe4N films have the potential applications in magneto- and electromechanical wearable spintronic devices.