Room Temperature Exchange Bias in Structure-Modulated Single-Phase Multiferroic Materials

Single-phase materials with room temperature (RT) exchange bias (EB) are very important for future applications in spintronic devices, magnetic storage, and sensors. However, such materials are rare because EB normally occurs with ferromagnetic (FM)/antiferromagnetic (AFM) boundaries. In this work, RT EB was realized by breaking the homogeneous structure of long-period Aurivillius oxides through a simple Fe/Ti content modulation. Fantastic intergrowth structures, with different neighboring layer numbers larger than 1, were first observed in this material system with optimized compositions. The intergrowth structure introduces a much larger lattice distortion and probability of Fe-O-Fe interaction, which can largely enhance the EB effect and the EB temperature. Most importantly, RT EB was finally realized in Bi10Fe6+gamma Ti3-gamma O30+delta (x = 0.2, 0.4) samples with the largest H-E of similar to 38 Oe measured at 300 K. Significantly, the concurring room temperature multiferroic behavior in such materials may add a new regulating factor for the EB through the application of an electrical field, which is meaningful for future device operations. The findings in this work alleviate the limitation of fabricating Aurivillius oxides with large layer numbers and shed new light on realizing room temperature EB in single-phase materials, with the potential for building future magnetically or electrically controlled spintronic devices.