Optically pumped magnetometers (OPM) are widely used for their exceptional sensitivity in detecting weak magnetic fields, with applications mainly in the biomedical field. However, their spatial resolution is limited by inherent factors such as vapor cell size, stand-off distance and magnetic noise, restricting their ability to spatially resolve small magnetic features. In this work, we investigate the potential of commercially available rod-shaped magnetic flux guides to address this limitation for magnetic fields perpendicular to a sample surface. Through simulations and experiments, we demonstrate that integrating flux guides into OPM systems can significantly enhance spatial resolution while maintaining sensitivity. We combine finite element simulations with measurements on current-driven meander structures of varying pitch and quantify performance via the minimum resolvable pitch and the magnetic flux transfer coefficient K. After applying a tailored demagnetization procedure to minimize residual magnetization and noise, the integrated OPM–flux-guide system reduces the minimum resolvable pitch from a 5 mm without a flux guide to 1 mm with a rod shaped flux guide with a diameter for 1 mm, at a magnetic contrast of 3.43 pT and an SNR of 18 dB. The spatial resolution was found to be constrained by the flux guide diameter and by spatial averaging over the finite OPM cell, consistent across simulations and experiments. These findings emphasize the importance of jointly selecting flux guide dimensions, magnetic state and sensor geometry. The results demonstrate resolution enhancement for controlled local magnetic-field patterns and provide a basis for future investigations of OPM-based magnetic sensing in applications such as non-destructive testing.
Magnetic tunnel junctions (MTJs) study in the past three decades, resulting in over 25,000 publications while adding 1000 more each year, has become among the most persuasive areas of research. MTJ devices lead the ubiquitous success of spintronics for technological advancement from most aspects of information technology to health sciences, with unprecedented, all-encompassing benefits to the society. We navigate through the evolution of the developing field of MTJs and the related technologies, with continued efforts for improving the tunnel magnetoresistance ratio. The MTJs' excellent ability to convert spin signals to charge signals secures their extensive commercial applications in magnetic data storage and field sensing. More advanced implementation and progress such as with neuromorphic and probabilistic computing entail from here.
Dy substitution is widely used to enhance the coercivity of Nd2Fe14B magnets; however, excessive Dy may introduce broad and heterogeneous switching-field distribution. This study identifies the compositional regime in which magnetic hardening is sustained before switching becomes strongly heterogeneous. Nd2DyxFe14B powders with x = 0, 0.2, 0.4, 0.6, and 0.8 were prepared by precipitation and reduction–diffusion treatment. Structural evolution, boundary segregation, and magnetic reversal were evaluated by X-ray diffraction, SEM/EDS, hysteresis-loop analysis, loop-work calculation, and descending-branch dM/dH analysis. The Nd2Fe14B-type matrix remained dominant, whereas the semi-quantitative Nd-rich XRD-area fraction increased from 0 to 11.37% with increasing Dy content, accompanied by progressive development of a patchy shell/intergranular network. Coercivity increased from 4.67 to 7.20 kOe, remanence from 66.95 to 80.70 emu g−1, and (BH)max from 5.62 to 9.38 MGOe. However, the switching-field width broadened from 3737.93 to 7613.93 Oe. Dy-3 retained the highest differential-susceptibility maximum despite substantial broadening, whereas Dy-4 exhibited the broadest reversal distribution and the lowest peak intensity. These results identify a transition between x = 0.6 and 0.8 from controlled hardening to strongly heterogeneous reversal. The study therefore establishes switching-field uniformity as a design parameter, in addition to coercivity and energy product, for optimizing Dy utilization in Nd2Fe14B permanent magnets.
Magnetic multilayers demonstrating magnetic anisotropy hold significant potential for a wide range of technological applications. In the quest for the advancement of magnetic devices, it is feasible to customize the physical properties of multilayered thin films through modifications to their interfaces, establishing a connection between microstructure, magnetic domain morphology, and high-frequency characteristics. In this study, the static magnetic characteristics of the samples were examined using first-order reversal curves (FORC) and magnetic domain images. The findings show that a substantial change in the static magnetic characteristics of the multilayer takes place when the cycle number exceeds 2. Furthermore, a cycle-number-dependent bimodal response is observed in the FORC distribution and permeability spectrum. The correlated FORC, magneto-optical Kerr effect (MOKE), and permeability signatures at n = 2 are consistent with magnetically distinguishable, incompletely synchronized response components. Across the series, the dominant resonance frequency shifts from 1.27 to 2.44 GHz. These observations support a coupling/heterogeneity interpretation but do not uniquely determine the strength or sign of the inter-repeat interaction or the dynamic mode character. The results establish cycle number as a structural variable for tuning the magnetic response of the investigated multilayers.
Simultaneous suppression of the skyrmion Hall effect (SkHE) and preservation of skyrmion topological integrity remain critical challenges for skyrmion-based racetrack devices. We propose a chirality-engineered racetrack architecture in which a Dzyaloshinskii–Moriya interaction (DMI) sign reversal creates an energy barrier with a dual function: preserving skyrmion integrity by preventing inter-skyrmion merger into stripe domains, and providing a repulsive force that counterbalances the Magnus force to suppress the SkHE. The barrier also enables helicity-based encoding and reconfigurable AND/OR logic. By tuning the transition width w, the device operates in two regimes: crosstalk-free transport for w>10nm, and logic operations via inter-skyrmion interactions for w≤10nm. For w≥20nm, topological charge Q≈2 is preserved throughout. Thiele-equation analysis identifies the off-diagonal SOT coupling integral Ixy as the governing velocity parameter. An optimal width w=20nm maximizes the threshold current density (Jth=2.7×1012A/m2) and steady-state velocity (v̄∼296m/s). Barrier-force model verification confirms the analytic prediction Fy=−2πRtFD0/w. This architecture provides a compact memory-logic integrated platform within a single racetrack.
