Magnetron Sputtering Synthesis of La‐Doped BiFeO ₃ Thin Films and Enhanced Exchange Bias in CoFeB/Bi _1‐x La _x FeO ₃ Heterostructures

Abstract Multiferroic BiFeO 3 (BFO) thin films have attracted significant attention for spintronic applications due to their strong magnetoelectric coupling at room temperature. However, the application of BFO remains at the laboratory stage, and low‐temperature, large‐scale preparation of BFO thin film still constitutes a challenge. In this study, the growth conditions of single‐crystalline BFO, La‐doped Bi 1‐x La x FeO 3 (BLFO), and ferromagnetic/BLFO heterostructures are optimized based on magnetron sputtering techniques. The following achievements are realized: 1) Epitaxial growth of BFO thin films at 440 °C, which is below the CMOS‐compatible temperature; 2) Optimization of La doping at 550 °C to enhance the epitaxial quality (ω scan FWHM = 0.12), reduce leakage current (J c ≈ 10 −2 mA cm − 2 ), and lower the ferroelectric switching voltage (1.83 V) of BLFO; 3) Achievement of a large exchange bias ( H ex = 85.1 Oe) with H ex /coercive field( H c )>1 in CoFeB/BLFO heterostructures. These achievements advance the broader application of BFO and lay the foundation for voltage‐controlled field‐free switching in ultra‐low‐power spintronic devices.