Soft magnetic nanocrystalline tape-wound cores are produced using the FAST/SPS process at different temperatures and pressures. The FAST/SPS method allows the adjustment of the hysteresis loop as a function of pressure. By controlling the temperature during compaction, both rectangular and flat hysteresis loops can be produced for the Vitroperm 800 alloy. The method is also applied to the Nanomet high-B alloy since high heating rates can also be used in the FAST/SPS process. The obtained Nanomet tape-wound cores combine a high saturation polarization of 1.6 T with a low coercivity of 7 A/m. A comparison with conventional electrical steel sheets for motors and transformers shows significantly lower losses for the Nanomet tape-wound core.
Superconducting spin valves (SSVs) based on ferromagnet/superconductor/ ferromagnet trilayers exploit the magnetic-state dependence of the superconducting transition temperature Tc, quantified here as ΔTc≡TcAP−TcP, where P and AP denote parallel and antiparallel magnetization states, respectively. Previous studies of metallic SSVs have mainly focused on in-plane magnetic anisotropy (IMA), while perpendicular magnetic anisotropy (PMA) systems remain less explored. Here, we realize a CoFeB/Nb/CoFeB SSV based on CoFeB/MgO interfacial PMA, exhibiting stable remanent parallel and antiparallel states at zero field together with a reproducible positive ∆Tc. Micromagnetic simulations suggest that reversal-induced multidomain states generate nonuniform stray fields, whereas uniform configurations provide a more homogeneous magnetostatic environment. The stable PMA remanent states highlight the potential of PMA to reduce magnetostatic complexity in superconducting spin valves. Dirty-limit coherence-length analysis gives dS/ξS,d=1.84 and 1.38 for the PMA and IMA samples, respectively, indicating effective exchange-field overlap in both structures, with quasiparticle-related processes and magnetic-state-dependent perturbations also contributing to the millikelvin-scale SSV response. Thus, the CoFeB/MgO-based PMA spin-valve platform provides stable and reproducible zero-field SSV states, while offering a route to reduce magnetostatic ambiguity associated with magnetization reversal.
This study evaluates the second-quadrant demagnetization curve which is essential for predicting the performance of Nd-Fe-B permanent magnets. It analyses the two-line geometric intersection method that reconstructs the main features of the demagnetization curve from only four points of the measured intrinsic curve (J-H). A reversible line, anchored at 0.2Hk and 0.7Hk, approximates the recoil-dominated region, while an irreversible line, anchored at 0.1Br and 0.5Br, captures the nucleation-dominated region; their intersection (Hψ, Jψ) and opening angle α define a compact set of descriptors, including a dimensionless form factor FF = 90°/α. The method was applied to four sintered Nd-Fe-B-based magnets spanning a squareness factor from 0.27 to 0.94 and a nearly fourfold range of intrinsic coercivity. The reconstructed remanence and intrinsic coercivity agree with experiment within 0.7% and 0.9%, respectively, and the enclosed curve area within 2.2%. The form factor correlates linearly with the experimental squareness factor (R2 = 0.99), offering a computationally inexpensive geometric proxy for the switching-field distribution that governs loop squareness, and the recoil permeability obtained from the reversible-line slope agrees with an independent estimate derived from Br and (BH)max within 1–7%. An efficiency metric ηmod = 1/μr, rising from 53.5% to 95.6% with squareness, links the reversible response directly to energy-product utilization. The knee field itself is not determined independently of prior experimental values. Keywords Magnetic propertiesKnee fieldMagnetsPowder metallurgyRare earthGeometric intersection
