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
In a ferrimagnet whose sublattices carry different Landé factors, the net moment and the net angular momentum vanish at different temperatures, the magnetization and angular-momentum compensation temperatures TM and TA. Mixed-spin lattice models conventionally evaluate one sum of the sublattice order parameters without Landé factors, which locates TA if the spin variable is an angular momentum. A generalized spin-S Blume–Capel-type model with spins 15/23/2 and Landé factors gDy=4/3 and gCo=2.2 is studied on a 147-site cuboctahedral core–shell cluster in mean field and by Monte Carlo simulation. In mean field the compensation point splits into TM=3.705 and TA=4.995, in units of the shell exchange JCo/kB. Ten Monte Carlo runs give 3.4896 and 4.76426 (run-to-run scatter). Here TA lies above the finite-cluster crossover and is defined only relative to the instantaneous shell moment; for weaker interface exchange or a thicker shell both points lie below the crossover and need no reference frame. If both points exist and the core-to-shell weight ratio decreases between them, TMgDy; this ordering held in all 229 of 576 parameter sets in which both exist. Equal Landé factors merge the pair. Scaled by the local slope of the weight ratio, the separations of 18 parameter sets collapse to within 11% for g contrasts up to 0.65. The window in which both exist is bounded: in mean field TA reaches the ordering temperature at analytic values of the interface exchange and core crystal field, and for a weakly coupled core a core fraction below 0.248 removes TM.
In this article, a magnetically tunable beam-steering flexible antenna array is designed and experimentally validated. A single transmission-line-based phase shifter is developed and realized on a flexible Kapton film with a thickness of 0.127 mm. The rear side of the substrate is covered with a double-sided conductive copper film, which serves as the ground plane. A ferrite disc made of Yttrium Iron Garnet (YIG) is placed between the substrate and the ground plane. Tunable phase-shifting characteristics are achieved by applying a magnetic bias perpendicular to the ferrite disc. A phase shift varying from 140 to 69 0 is obtained for different magnetic fields ranging from 0.1 Tesla to 0.2 Tesla. This phase-shifter concept is utilized to design a beam-steering antenna array operating in the X-band region. A 4 × 4 antenna array is designed on a Kapton substrate of dimensions 70 mm × 70 mm using a corporate feed network. The YIG discs developed in the laboratory are placed under various junctions of the feed network between the substrate and the ground plane. The antenna array operates in the X-band with a bandwidth of 720 MHz (9.88–10.6 GHz), centered at 10.1 GHz. The proposed flexible antenna also exhibits circular polarization at 10.5 GHz and 10 GHz without bias and with bias respectively. External magnetic bias is applied using small and strong Neodymium (Nd) magnets capable of generating higher magnetic fields. With a positive bias, the proposed antenna array can steer the beam up to 250 in one direction, and with reverse bias, it can steer up to 300 in the opposite direction. The proposed beam-steering array is suitable for flexible X-band applications.
Spin-orbit-torque (SOT) magnetic tunnel junctions (MTJs) provide a way to generate random bits with tunable output probabilities. Here, we use MuMax3 simulations to study probability control by SOT pulses and an out-of-plane magnetic field. The pulses drive the free layer towards a high-energy transient state, followed by thermally assisted relaxation into parallel or antiparallel states. The external field biases the final state and continuously tunes the P-state probability. Within the tested ranges, current-amplitude and pulse-width variations have limited effects, whereas temperature causes systematic probability drift. We therefore implement temperature-informed field control with probability-feedback triggering and an adaptive sensitivity factor. Across 100 paired simulation runs, the controller reduces the mean absolute error of the 100-bit probability estimate from 0.0522 to 0.0376. The device supports an unbiased TRNG mode and intentionally biased Bernoulli outputs for stochastic computing. These results establish micromagnetic probability control and controller-level compensation.
