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1. Interface induced uniaxial magnetic anisotropy and modified domain patterns in crosslinked silica aerogel/Ni80Fe20 heterostructures

   https://doi.org/10.1007/s00339-025-08449-3  

   Islam, K_Z; Timsina, D.; Sabri, F.; Pollard, S_D (March 2025, Applied Physics A)

   Abstract Silica aerogels have emerged as promising candidates as platforms for a variety of devices, including those used for magnetic logic and sensing. However, their non-planar structure also poses challenges for their use as substrates for thin film devices. For example, substrate disorder is established to strongly influence anisotropy in thin film magnetic materials. Here, we evaluate the substrate effect on induced uniaxial anisotropy in permalloy (Py) thin films and patterned structures, wherein the uniaxial anisotropy is clearly linked to a directionality of the magnetization hysteresis and modifications to zero field domain structures relative to a standard thermally oxidized Si substrate. The strength and direction of this anisotropy vary with location, indicating its non-uniform nature, and is estimated to be as large as 700 J/m³for 25 nm thick permalloy films, and decreases with increasing Py thickness. This substrate induced anisotropy is strong enough to modify the domain structures present in patterned magnetic elements and can have significant implications for the development of magnetic devices on aerogel substrates. Results are compared and found to be consistent with micromagnetic modelling of expected domain structures. 

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2. Direct current magnetic Hall probe technique for measurement of field penetration in thin film superconductors for superconducting radio frequency resonators

   https://doi.org/10.1063/5.0083309  

   Senevirathne, I. H.; Gurevich, A.; Delayen, J. R. (May 2022, Review of Scientific Instruments)

   Superconducting Radio Frequency (SRF) cavities used in particle accelerators are typically formed from or coated with superconducting materials. Currently, high purity niobium is the material of choice for SRF cavities that have been optimized to operate near their theoretical field limits. This brings about the need for significant R & D efforts to develop next generation superconducting materials that could outperform Nb and keep up with the demands of new accelerator facilities. To achieve high quality factors and accelerating gradients, the cavity material should be able to remain in the superconducting Meissner state under a high RF magnetic field without penetration of quantized magnetic vortices through the cavity wall. Therefore, the magnetic field at which vortices penetrate a superconductor is one of the key parameters of merit of SRF cavities. Techniques to measure the onset of magnetic field penetration on thin film samples need to be developed to mitigate the issues with the conventional magnetometry measurements that are strongly influenced by the film orientation and shape and edge effects. In this work, we report the development of an experimental setup to measure the field of full flux penetration through films and multi-layered superconductors. Our system combines a small superconducting solenoid that can generate a magnetic field of up to 500 mT at the sample surface and three Hall probes to detect the full flux penetration through the superconductor. This setup can be used to study alternative materials that could potentially outperform niobium, as well as superconductor–insulator–superconductor (SIS) multilayer coatings on niobium. 

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3. Functional Janus structured liquids and aerogels

   https://doi.org/10.1038/s41467-023-43319-7  

   Ghaffarkhah, Ahmadreza; Hashemi, Seyyed Alireza; Ahmadijokani, Farhad; Goodarzi, Milad; Riazi, Hossein; Mhatre, Sameer E; Zaremba, Orysia; Rojas, Orlando J; Soroush, Masoud; Russell, Thomas P; et al (December 2023, Nature Communications)

   Abstract Janus structures have unique properties due to their distinct functionalities on opposing faces, but have yet to be realized with flowing liquids. We demonstrate such Janus liquids with a customizable distribution of nanoparticles (NPs) throughout their structures by joining two aqueous streams of NP dispersions in an apolar liquid. Using this anisotropic integration platform, different magnetic, conductive, or non-responsive NPs can be spatially confined to opposite sides of the original interface using magnetic graphene oxide (mGO)/GO, Ti₃C₂T_x/GO, or GO suspensions. The resultant Janus liquids can be used as templates for versatile, responsive, and mechanically robust aerogels suitable for piezoresistive sensing, human motion monitoring, and electromagnetic interference (EMI) shielding with a tuned absorption mechanism. The EMI shields outperform their current counterparts in terms of wave absorption, i.e., SE_T ≈ 51 dB, SE_R ≈ 0.4 dB, and A = 0.91, due to their high porosity ranging from micro- to macro-scales along with non-interfering magnetic and conductive networks imparted by the Janus architecture. 

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4. Optimizing time-resolved magneto-optical Kerr effect for high-fidelity magnetic characterization

   https://doi.org/10.1063/5.0275720  

   Kim, Yun; Huang, Dingbin; Lyu, Deyuan; Sun, Haoyue; Wang, Jian-Ping; Crowell, Paul A; Wang, Xiaojia (July 2025, Applied Physics Letters)

   Spintronics has emerged as a key technology for fast and nonvolatile memory with great CMOS compatibility. As the building blocks for these cutting-edge devices, magnetic materials require precise characterization of their critical properties, such as the effective anisotropy field (Hk,eff, related to magnetic stability) and damping (α, a key factor in device energy efficiency). Accurate measurements of these properties are essential for designing and fabricating high-performance spintronic devices. Among advanced metrology techniques, time-resolved magneto-optical Kerr effect (TR-MOKE) stands out for its superb temporal and spatial resolutions, surpassing traditional methods like ferromagnetic resonance. However, the full potential of TR-MOKE has not yet been fully fledged due to the lack of systematic optimization and robust operational guidelines. In this study, we address this gap by developing experimentally validated guidelines for optimizing TR-MOKE metrology across materials with perpendicular magnetic anisotropy and in-plane magnetic anisotropy. While Co20Fe60B20 thin films are used for experimental validation, this optimization framework can be readily extended to a variety of materials such as L10-FePd with easy-axis dispersion. Our work identifies the optimal ranges of the field angle to simultaneously achieve high signal amplitudes and improve measurement sensitivities to Hk,eff and α. By suppressing the influence of inhomogeneities and boosting sensitivity, our work significantly enhances TR-MOKE capability to extract magnetic properties with high accuracy and reliability. This optimization framework positions TR-MOKE as an indispensable tool for advancing spintronics, paving the way for energy-efficient and high-speed devices that will redefine the landscape of modern computing and memory technologies. 

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5. Distortion-free inside-out imaging for rapid diagnostics of rechargeable Li-ion cells

   https://doi.org/10.1073/pnas.1906976116  

   Romanenko, Konstantin; Jerschow, Alexej (September 2019, Proceedings of the National Academy of Sciences)

   Safety risks associated with modern high energy-dense rechargeable cells highlight the need for advanced battery screening technologies. A common rechargeable cell exposed to a uniform magnetic field creates a characteristic field perturbation due to the inherent magnetism of electrochemical materials. The perturbation pattern depends on the design, state of charge, accumulated mechanical defects, and manufacturing flaws of the device. The quantification of the induced magnetic field with MRI provides a basis for noninvasive battery diagnostics. MRI distortions and rapid signal decay are the main challenges associated with strongly magnetic components present in most commercial cells. These can be avoided by using Single-Point Ramped Imaging with T 1 enhancement (SPRITE). The method is immune to image artifacts arising from strong background gradients and eddy currents. Due to its superior image quality, SPRITE is highly sensitive to defects and the state of charge distribution in commercial Li-ion cells. 

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