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    Fabrication and characterization of a Vacodur49/PZT/Vacodur49 magnetoelectric sensor
    (Elsevier, 2025) Durmaz, Ergun; Inan, Orhan Orcun; Atalay, Selcuk
    In this study, we report for the first time the fabrication and characterization of a Vacodur49/PZT/Vacodur49 trilayer magnetoelectric (ME) sensor. Vacodur49, a cobalt-iron-vanadium alloy, was employed as the magnetostrictive component due to its high saturation magnetization and significant magnetostriction (70 ppm). Structural and magnetic analyses confirmed the crystalline quality, magnetic softness, and favourable anisotropy of the alloy. The fabricated device exhibited a strong resonance-enhanced ME coupling, achieving a maximum ME coefficient of 361 V center dot cm(-1)center dot Oe(-1) under an AC magnetic field of 0.047 Oe at similar to 49.2 kHz. The sensor demonstrated ultra-high sensitivity with a minimum detectable AC magnetic field of 100 pT, excellent linearity, and fast response. Compared to many other magnetic materials, Vacodur49 provides superior mechanical robustness and enables thicker magnetostrictive layers. These results establish Vacodur49 as a novel and promising material platform for next-generation ME sensors, with potential applications in biomedical diagnostics, ultra-low-field detection, and precision magnetic sensing technologies.
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    Structural evolution and microwave absorption properties of MnFe2O4/BaTiO3 nanoparticle systems and their composites
    (Springer, 2026) Atalay, Selcuk; Durmaz, Ergun; Seker, Omer Faruk
    In this study, MnFe2O4/BaTiO3 nanoparticle systems were systematically investigated as microwave absorbers in the X-band (8-12.4 GHz). Nanoparticles were physically mixed at different weight ratios and examined both before and after annealing at 1100 C for 3 h. The microstructural and magnetic properties were evaluated using SEM, TEM, XRD, XPS, FTIR and M-H hysteresis measurements, respectively. Structural analyses revealed that the as-mixed samples consist of coexisting MnFe2O4 and BaTiO3 phases, while annealing induces an in-situ transformation into an Mn/Ti-substituted M-type barium hexaferrite phase. This phase evolution leads to a significant increase in saturation magnetization and coercivity, indicating a transition toward harder magnetic behavior. Microwave absorption performance was evaluated using reflection loss measurements. The non-annealed 50 MnFe2O4-50 BaTiO3 composite exhibits the best absorption performance, with a minimum reflection loss (RL) of approximately - 23 dB at 10.8-11.0 GHz. In contrast, annealed samples show reduced absorption efficiency, with minimum reflection loss values in the range of - 10 to - 16 dB. These results demonstrate that enhanced magnetic hardness does not necessarily improve microwave absorption in MnFe2O4/BaTiO3-based absorbers.