Rui Hu,Yan Zhao,Ying Zhang,Xusheng Wang,Guorong Li,Mingxue Deng
The demand for multidimensional stimulus sensing devices that can be used for the real-time monitoring of the equipment status in complex working environments has led to investigations on multifunctional optoelectronic materials. Nevertheless, the exploitation of all-in-one materials with multimode and multicolor luminescence capacities is still immature. Given the abundant transitions in lanthanide ions and the stress-responsive ability of piezoelectric crystals, multi-activator-doped piezoelectric materials are promising candidates for multifunctional detection based on luminescence characteristics. Herein, we report a novel multidimensional stimulus-sensitive material constructed via combining dual luminescence centers (Bi3+/Er3+) with piezoelectric LiTaO3, thus realizing opto-mechano-thermo-responsive luminescence in a single material. Particularly the photoluminescence is allochroic (cyangreen-yellow) under diverse excitation sources (ultraviolet-blue-near infrared radiation). Its mechanoluminescence performance shows a linear relation with the applied load, allowing its application in stress sensing. In addition, the thermally coupled levels of Er3+ dopants endow the LiTaO3 material with temperature sensing capacity relying on the fluorescence intensity ratio. These findings provide a new method for designing optical function materials and integrated optoelectronic devices toward radiative, stress, and temperature sensing applications.
Single-phase materials with exchange bias (EB) effect at room temperature (RT) are very important for future applications in spintronic devices, magnetic storage, and sensors. To explore materials showing the EB effect at RT is an interesting and important issue. In this paper, LaFeO 3 micro-polyhedrons composed of an average particle size of 66 nm nanoparticles have been synthesized by annealing LaFe(CN) 6 precursors in air at 630 °C for 8 h. Magnetic hysteresis loops show that LaFeO 3 micro-polyhedrons present a large spontaneous EB (SEB) effect ( ∼ 1.5 kOe) at RT after zero-field cooling (ZFC) and a gigant conventional EB (CEB) effect ( ∼ 5.6 kOe) after field cooling (FC) of 70 kOe. To the best of our knowledge, the current compound shows the largest negative EB field after ZFC at RT among SEB materials discovered so far. The successful fitting of training effect (TE) data with Binek’s model shows that the origin of SEB lies in the interface exchange coupling between different magnetic phases. The interface with the “pinning” effect of antiferromagnetic (AFM) matrix relative to ferromagnetic (FM) clusters exhibits unidirectional anisotropy, which is formed during the initial magnetization process. This interesting finding of the SEB effect at RT in single-phase perovskite LaFeO 3 system may open a new direction for possible technological applications.
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