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   https://doi.org/10.1016/j.jmbbm.2021.104587  

   Zampini, Marco Andrea ; Guidetti, Martina ; Royston, Thomas J. ; Klatt, Dieter ( August 2021 , Journal of the Mechanical Behavior of Biomedical Materials)

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   https://doi.org/DOI: 10.1080/10739149.2017.1401547  

   Qinglei Meng, Michael Daugherty ( December 2017 , Instrumentation science & technology)

   Transcranial magnetic stimulation (TMS) is widely used for noninvasive brain stimulation. However, existing TMS tools cannot deliver targeted neural stimulation to deep brain regions, even though many important neurological disorders originate from there. To design TMS tools capable of delivering deep and focused stimulation, we have developed both electric and magnetic field probes to evaluate and improve new designs and calibrate products. Previous works related to magnetic field measurement had no detailed description of probe design or optimization. In this work, we demonstrated a magnetic field probe made of a cylindrical inductor and an electrical field probe modified from Rogowski coil structure. Both have much smaller size and higher directivity than commercial dipole probes. Using probe, we can calibrate and monitor any new types of TMS coil or array design and verify measured results with the other probe. We mathematically analyze their characteristics and performance and obtained a two-dimensional vector plot of the induced electric field, which matched the measured results from the second type of probe. A commercial circular coil and a figure-8 coil, with relatively complex vector field distribution, were used as examples to demonstrate the high-resolution and accurate measurement capability of our probes. 

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5. Native Oxidation and Complex Magnetic Anisotropy‐Dominated Soft Magnetic CoCrFeNi‐Based High‐Entropy Alloy Thin Films

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   Zhang, Junyi ; Wang, Xiao ; Li, Xiaona ; Zheng, Yuehong ; Liu, Renwei ; Luan, Junhua ; Jiao, Zengbao ; Dong, Chuang ; Liaw, Peter K. ( October 2022 , Advanced Science)

   Soft magnetic high‐entropy alloy thin films (HEATFs) exhibit remarkable freedom of material‐structure design and physical‐property tailoring, as well as, high cut‐off frequencies and outstanding electrical resistivities, making them potential candidates for high‐frequency magnetic devices. In this study, a CoCrFeNi film with excellent soft magnetic properties is developed by forming a novel core–shell structure via native oxidation, with ferromagnetic elements Fe, Co, and Ni as the core and the Cr oxide as the shell layer. The core–shell structure enables a high saturation magnetization, enhances the electrical resistivity, and thus reduces the eddy‐current loss. For further optimizing the soft magnetic properties, O is deliberately introduced into the HEATFs, and the O‐incorporated HEATFs exhibit an electrical resistivity of 237 µΩ·cm, a saturation magnetization of 535 emu cm⁻³, and a coercivity of 23 A m⁻¹. The factors that determine the ferromagnetism and coercivity of the CoCrFeNi‐based HEATFs are examined in detail by evaluating the microstructures, magnetic domains, chemical valency, and 3D microscopic compositional distributions of the prepared films. These results are anticipated to provide insights into the magnetic behaviors of soft magnetic HEATFs, as well as aid in the construction of a promising material‐design strategy for these unique materials.

    

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