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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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Ferroelectric Materials - Synthesis and Characterization || Biasing Effects in Ferroic Materials
摘要： In this chapter we present an overview of some important concepts related to the processes and microstructural mechanisms that produce the deformation of hysteresis loops and the loss of their symmetry characteristics in ferroelectric, ferroelastic and ferromagnetic systems. The most discussed themes include: aging and fatigue as primary mechanisms of biased hysteresis loops in ferroelectric/ferroelastic materials, imprint phenomenon as an important biasing process in ferroelectric thin films, the development of an exchange bias field and of specific spin states, such as spin canting and spin-glass-like phases, as the main causes of biased hysteresis loops in different types of magnetic heterostructures. The present discussion leads to the identification of the main differences and possible analogies in the underlying mechanisms of possible biasing effects occurring in the different ferroic systems, which can benefit the theoretical description, modelling, and engineering of multifunctional devices based on ferroic systems experiencing the internal bias phenomena.
关键词： Aging,exchange bias,internal field,fatigue,imprint
更新于2025-09-23 15:21:01
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The challenge in realizing an exchange coupled BiFeO3- double perovskite bilayer
摘要： In this work we propose a device design for efficient voltage control of magnetism. The magnetization of a ferrimagnetic double perovskite may be manipulated by an exchange coupled layer of multiferroic BiFeO3. Bilayers of Barium doped BiFeO3 and ferrimagnetic double perovskite Sr2FeMoO6 have been prepared by pulsed laser deposition motivated by the possibility of strong interlayer exchange coupling. While single layers of each material show high quality we observe that in both stacking orders the first layer decomposes during the deposition of the second layer. The reason for the decomposition are strongly differing growth conditions for BiFeO3 and Sr2FeMoO6. This means that the generation of artificial multiferroic stacks requires careful choice of the constituent materials to ensure the bilayer stability.
关键词： BiFeO3,Exchange Bias,Double Perovskite,Perovskite,Sr2FeMoO6,Exchange coupling
更新于2025-09-23 15:19:57
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Effect of cobalt substitution on the multiferroic characteristics of ferroelectric potassium sodium niobate (K0.5Na0.5NbO3) ceramics
摘要： The room-temperature multiferroic behavior of cobalt-substituted KNN [K0.5Na0.5Nb1?xCoxO3, 0.02 ≤ x ≤ 0.05] ceramics has been investigated. Both the X-ray diffraction and selected area electron diffraction analysis confirm that all the compositions found to be crystallized in the single phase (Orthorhombic, Amm2) without any formation of cobalt clusters and/or other secondary phases such as Co3O4. Co2+ oxidation state and the presence of oxygen vacancies in the samples have been studied through X-ray photoelectron spectroscopic measurements. The changes in the bandgap with the increase of Co concentration in KNN are noticed from UV–Visible absorption spectroscopy. Magnetic measurement on the samples reveals a dominant antiferromagnetic interaction attributed to the Co2+–Co2+ exchange interactions via F0-center and coupling between Co2+–Co2+ through O2?. The existence of exchange bias (EB) effect is also observed in KNaNb1?xCoxO3 (x = 0.03, 0.04, 0.05) samples from the magnetic measurements. In addition, it is found that defect complexes formed between Co′′′ Nb and oxygen vacancy lead to the enhanced dielectric, ferro, and piezoelectric properties of K0.5Na0.5Nb1?xCoxO3 ceramics.
关键词： Multiferroic,Cobalt-substituted KNN,Ferroelectric,Exchange bias,Antiferromagnetic
更新于2025-09-10 09:29:36