Tailoring magnetic anisotropy via built-in strain in thin films

Although engineering built-in strain in materials is strategically important for tuning their functional properties, conventional approaches based on epitaxial lattice mismatch are constrained by the specific combinations of materials and underlayers, thereby restricting material selection. In this study, we propose a method to introduce built-in strain into nano-thin films deposited on flexible substrates. By mechanically stretching the substrate during film deposition, a uniaxial compressive built-in strain is induced into the film upon release of the strain. We applied this technique to tailor the magnetic anisotropy of Co and Ni thin films. Systematic modulation of in-plane magnetic anisotropy was observed as a function of the magnitude of the built-in strain. Furthermore, we fabricated a giant magnetoresistive (GMR) device with orthogonally aligned magnetizations in the pinned and free layers. The device exhibited a linear resistance response to external magnetic fields—a characteristic feature of GMR devices with orthogonal magnetization configurations. The proposed method is simple yet versatile for strain engineering, offering a promising route not only for enhancing spintronic device performance but also for exploring strain-induced physical phenomena in functional materials.