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Giant exchange bias in the single-layered Ruddlesden-Popper perovskite
摘要： Exchange bias (EB) as large as ～5.5 kOe is observed in SrLaCo0.5Mn0.5O4, which is the highest ever found in any layered transition-metal oxides including Ruddlesden-Popper series. Neutron-diffraction measurement rules out long-range magnetic ordering and together with dc magnetic measurements suggests formation of short-range magnetic domains. Ac magnetic susceptibility, magnetic memory effect, and magnetic training effect con?rm the system to be a cluster spin glass. By carrying out density functional calculations on several model con?gurations, we propose that EB is originated at the boundary between Mn-rich antiferromagnetic and Co-rich ferromagnetic domains at the subnanoscale. Reversal of magnetization axis on the Co side alters the magnetic coupling between the interfacial Mn and Co spins, which leads to EB. Our analysis infers that the presence of competing magnetic interactions is suf?cient to induce exchange bias and thereby a wide range of materials exhibiting giant EB can be engineered for designing novel magnetic memory devices.
关键词： Ruddlesden-Popper perovskite,Exchange bias,cluster spin glass,magnetic memory devices
更新于2025-09-23 15:21:21
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Quantum dots of two-dimensional Ruddlesdena??Popper organica??inorganic hybrid perovskite with high optical limiting properties
摘要： Hybrid perovskites have been investigated for various potential applications because of their tunable optical properties. In this paper, we report the synthesis of quantum dots (QDs) of two-dimensional (2D) Ruddlesden–Popper (RP) hybrid perovskite using a top-down approach. The QDs of the developed 2D RP perovskite exhibit high and sharp photoluminescence in the ultraviolet region. The sharp peak in the absorption spectrum and the intense photoluminescence in the ultraviolet region indicate strong quantum confinement in these particles, which is further confirmed by x-ray photoelectron spectroscopy. These QDs show superior nonlinear optical scattering and absorption properties with the optical z-scan technique and strong nonlinear absorption property with the photoacoustic z-scan technique. Evaluating the nonlinear optical properties using two complementary techniques provides a deeper understanding of the nonlinear mechanism involved in the optical limiting process. The two-photon absorption coefficient obtained by optical z-scan is 7.2 × 102 cm/GW, which is larger than that of most perovskite nanocrystals and nanosheets. Our studies, therefore, reveal a new class of material, 2D RP perovskite QDs, which show important nonlinear properties that are important for optical limiting applications.
关键词： Ruddlesden–Popper perovskite,optical limiting,nonlinear optical properties,Quantum dots,two-photon absorption
更新于2025-09-23 15:21:01