Magnetic Orientation Research Articles

Ternary stochastic neuron- implemented with a single strained magnetostrictive nanomagnet.

Stochastic neurons are extremely efficient hardware for solving a large class of problems and usually come in two varieties - 'binary' where the neuronal state varies randomly between two values of ±1 and 'analog' where the neuronal state can randomly assume any value between -1 and +1. Both have their uses in neuromorphic computing and both can be implemented with low- or zero-energy-barrier nanomagnets whose random magnetization orientations in the presence of thermal noise encode the binary or analog state variables. In between these two classes isn-ary stochastic neurons, mainly ternary stochastic neurons (TSNs) whose state randomly assumes one of three values (-1,0,+1), which have proved to be efficient in pattern classification tasks such as recognizing handwritten digits from the MNIST data set or patterns from the CIFAR-10 data set. Here, we show how to implement a TSN with a zero-energy-barrier (shape isotropic) magnetostrictive nanomagnet subjected to uniaxial strain.

The Optical Extinction Law Depends on Magnetic Field Orientation: The RV–ψ Relation

Abstract For aspherical interstellar dust grains aligned with their short axes preferentially parallel to the local magnetic field, the amount of extinction per grain is larger when the magnetic field is along the line of sight and smaller when in the plane of the sky. To the extent that optical extinction arises from both aligned and unaligned grain populations with different extinction properties, changes in the magnetic field orientation induce changes in its wavelength dependence, parameterized by R V ≡ A V /E(B − V). We demonstrate that the measured total and polarized extinction curves of the diffuse Galactic interstellar medium imply R V varies from 3.21 when the magnetic field is along the line of sight (ψ = 0) to R V = 3.05 when in the plane of the sky (ψ = 90°). This effect could therefore account for much of the large-scale R V variation observed across the sky (σ(R V ) ≃ 0.2), particularly at high Galactic latitudes.

Spin transfer torque switching in double magnetic tunnel junctions based on dual MgO layers

We report fabrication and characterization of double magnetic tunnel junction (DMTJ) magneto-resistive random access memory cells that exhibit characteristic about 2X reduction of switching current compared to single reference layer junctions, but maintain high tunneling magnetoresistance ratio exceeding 120 %, high coercive fields of the free layer of more than 2 kOe for 65 nm cells, and magnetically stable reference layers with pinning fields above 6 kOe. Switching analysis performed for two different relative magnetization orientations of the reference layers shows that the net switching current is the result of combined spin transfer torque effects of the individual reference layers, with tunneling and spin-valve-like contributions adding constructively. Our work shows that efficient reduction of switching current can be achieved in double magnetic tunnel junctions with dual MgO layers where one of the layers has significantly lower resistance-area product to enable high magnetoresistance ratio.

Magnetic Field-Assisted Orientation and Positioning of Magnetite for Flexible and Electrically Conductive Sensors.

Magnetic field-assisted control of magnetite location is a promising strategy for developing flexible, electrically conductive sensors with enhanced performance and adjustable properties. This study investigates the effect of static magnetic fields applied on thermoplastic elastomer (TPE) composites with magnetite and multi-walled carbon nanotubes (MWCNT). The composites were prepared by compression moulding and the magnetic field was applied on the mould cavity during processing. Composites were prepared with a range of concentrations of magnetite (1, 3, and 6 wt.%) and MWCNT (1 and 3 wt.%). The effect of particle concentration on composite viscosity was investigated. Rheological analysis showed that MWCNTs significantly increased the composite viscosity while magnetite had minimal impact, ensuring stable processing and facilitating particle orientation under a static magnetic field. Particle orientation and electrical conductivity were evaluated for the composites prepared with different particle concentrations under different processing temperatures. Magnetic field application at 190 °C enhanced magnetite/MWCNT interactions, substantially reducing electrical resistivity while preserving thermal stability. The composites showed no degradation at 220 °C and above, demonstrating suitability for high-temperature applications requiring thermal resilience. Furthermore, magnetite's magnetic response facilitated precise sensor positioning and strong adhesion to polyimide substrates at 220 °C. These findings demonstrate a scalable and adaptable approach for enhancing sensor performance and positioning, with broad potential in flexible electronics.

Classifying the Magnetosheath Using Local Measurements From MMS

AbstractThe Earth's magnetosheath is a dynamic region of shocked solar wind plasma downstream of the bow shock. Depending on the upstream magnetic field orientation, the magnetosheath usually has one of two distinct configurations: a more variable magnetosheath with strong fluctuations and structures propagating from upstream to downstream, or a more stationary magnetosheath characterized by compression and high ion temperature anisotropy. The more variable magnetosheath is usually observed for quasi‐parallel shocks (the angle between the shock normal and the upstream magnetic field ), but the limit can vary for . These differences facilitate studies of how different plasma environments affect various processes such as turbulence and heating, and these require an accurate magnetosheath classification. Since can rarely be determined correctly in the absence of upstream monitors, local measurements have been suggested to classify the magnetosheath. However, this has not yet been verified for Magnetospheric Multiscale (MMS) data. We investigate this approach with MMS using locally measured magnetic field variability, ion temperature anisotropy, and suprathermal ion flux. We find the more variable magnetosheath at normalized magnetic fluctuations above 0.29 and ion temperature anisotropy below 0.18. We also find that the suprathermal ion flux can complement the classification given that MMS burst‐mode data is used. Our findings provide a method to determine the magnetic connectivity of the magnetosheath with the upstream solar wind in the case of MMS and classify the downstream region into different configurations.

SOFIA/HAWC+ Far-infrared Polarimetric Large-area CMZ Exploration Survey. IV. Relative Magnetic Field Orientation throughout the CMZ

Abstract The nature of the magnetic field structure throughout the Galactic Center (GC) has long been of interest. The recent Far-InfraREd Polarimetric Large-Area Central Molecular Zone (CMZ) Exploration (FIREPLACE) Survey reveals preliminary connections between the seemingly distinct vertical and horizontal magnetic field distributions previously observed in the GC. We use the statistical techniques of the Histogram of Relative Orientation and the Projected Rayleigh Statistic to assess whether the CMZ magnetic field preferentially aligns with the structure of the CMZ molecular clouds or the morphology of the nonthermal emission of the GC nonthermal filament (NTF) population. We find that there is a range of magnetic field orientations throughout the population of CMZ molecular clouds, ranging from parallel to perpendicular orientation. We posit these orientations depend on the prevalence of gravitational shear in the GC, in contrast with what is observed in Galactic Disk star-forming regions. We also compare the magnetic field orientation from dust polarimetry with individual prominent NTFs, finding a preferred perpendicular relative orientation. This perpendicular orientation indicates that the vertical field component found in the FIREPLACE observations is not spatially confined to the NTFs, providing evidence for a more pervasive vertical field in the GC. From dynamical arguments, we estimate an upper limit on the magnetic field strength for this vertical field, finding B ≤ 4 mG. A field close to this upper limit would indicate that the NTFs are not local enhancements of a weaker background field and that the locations of the NTFs depend on proximity to sites of cosmic-ray production.

Full voltage control of giant magnetoresistance

The aim of voltage control of magnetism is to reduce the power consumption of spintronic devices. For a spin valve, the relative magnetic orientation for the two ferromagnetic layers is a key factor determining the giant magnetoresistance (GMR) ratio. However, achieving full voltage manipulation of the magnetization directions between parallel and antiparallel states is a significant challenge. Here, we demonstrate that by utilizing two exchange-biased Co/IrMn bilayers with opposite pinning directions and with ferromagnetic interlayer coupling between the two Co layers, the magnetization alignment of the two Co layers of a spin valve can be switched between antiparallel and nearly parallel states by voltage-induced strain, leading to a full voltage control of GMR in a repeatable manner. The magnetization rotating processes for the two Co layers under different voltages can be clearly demonstrated by simulations based on the Landau–Lifshitz–Gilbert equation. This work provides valuable references for the development of full voltage-controlled spintronic devices with low energy consumption.

Spectroscopic Signatures of Phonon Character in Molecular Electron Spin Relaxation.

Spin-lattice relaxation constitutes a key challenge for the development of quantum technologies, as it destroys superpositions in molecular quantum bits (qubits) and magnetic memory in single molecule magnets (SMMs). Gaining mechanistic insight into the spin relaxation process has proven challenging owing to a lack of spectroscopic observables and contradictions among theoretical models. Here, we use pulse electron paramagnetic resonance (EPR) to profile changes in spin relaxation rates (T 1) as a function of both temperature and magnetic field orientation, forming a two-dimensional data matrix. For randomly oriented powder samples, spin relaxation anisotropy changes dramatically with temperature, delineating multiple regimes of relaxation processes for each Cu(II) molecule studied. We show that traditional T 1 fitting approaches cannot reliably extract this information. Single-crystal T 1 anisotropy experiments reveal a surprising change in spin relaxation symmetry between these two regimes. We interpret this switch through the concept of a spin relaxation tensor, enabling discrimination between delocalized lattice phonons and localized molecular vibrations in the two relaxation regimes. Variable-temperature T 1 anisotropy thus provides a unique spectroscopic method to interrogate the character of nuclear motions causing spin relaxation and the loss of quantum information.

A study of the magnetoelastic effect in metallic textured NiW<sub><i>x</i></sub> (x = 5.5, 6.0, 7.4, AND 7.7 at %) ribbons

the dependence of the differential magnetic susceptibility cac(T) of metallic biaxially textured NiWx ribbons with a tungsten content x = 5.5, 6.0, 7.4, 7.7 at% on plane mechanical tension and compressive stresses has been studied in the temperature range 50–350 K. To create the tensile and compressive stresses, the thermal cycling procedure is applied to the ribbons glued to the substrates made of Si and aluminum alloy D16T, respectively. It is shown that the main peculiarities of the magnetic susceptibility behavior can be explained by magnetic orientation transitions and the occurrence of internal stresses s(T) that exceed the elastic limit of NiWx.

A Compact Piezo-Drive Rotatable Scanning Tunneling Microscope in a 12 T Cryogen-Free Magnet.

Atomically resolved scanning tunneling microscope (STM) capable of insitu rotation in a narrow magnet bore has become a long-awaited but challenging technique in the field of strong correlation studies since it can introduce the orientation of the strong magnetic field as a control parameter. This article presents the design and functionality of a piezoelectrically driven rotatable STM (RSTM), operating within a 12 T cryogen-free magnet and achieving a base temperature below 1.8 K, along with spectroscopic capabilities. The system features a compact STM head unit that combines an inertia drive shaft with spring clamping onto the inner wall of a slender piezoelectric scanning tube (PST), enabling both stepper and scanner functionality while reducing the STM's size to 25.5 mm in length and 9 mm in diameter, facilitating rotation within the magnet bore. Another linear piezoelectric motor, driven by a PST, employs a mechanical linkage to convert linear into rotational motion, driving the STM head unit coaxially aligned with it. This mechanism enables STM accurate rotation, offering angle control from 0° to 90° with an ideal closed-loop accuracy of 0.11° per 0.01 V, as determined by a calibrated Hall sensor. Compact and suspended as a standalone unit at the tail of the sample probe, the RSTM is effectively shielded from external mechanical vibrations via secondary counterweight damping. To validate the device performance, the topographic images of graphite and NbSe2 and their spectroscopy at various magnetic field orientations up to 12 T and temperatures below 1.8 K are obtained. The compact and vibration-resistant RSTM provides compatibility with ultra-high-field water-cooled magnets, facilitating investigations into multiangle magnetic field modulation studies for condensed matter physics.

Cataglyphis ants have a polarity-sensitive magnetic compass.

Spatial orientation based on the geomagnetic field (GMF) is a widespread phenomenon in the animal kingdom, predominantly observed in long-distance migrating birds,1 sea turtles,2 lobsters,3 and Lepidoptera.4,5 Although magnetoreception has been studied intensively, the mechanism remains elusive. A crucial question for a mechanistic understanding of magnetoreception is whether animals rely on inclination or polarity-based magnetic information. Inclination-based magnetic orientation utilizes the angle between the magnetic field lines and gravity, indicating poleward and equatorward. In contrast, polarity-based magnetic orientation allows animals to detect the polarity of the GMF, the north and south direction of the field vector. Cataglyphis desert ants are excellent experimental models for testing whether magnetic inclination or polarity of the magnetic field is used for navigation. Desert ants are solitary foragers with exceptional navigational skills.6 When the ants leave their underground nest for the first time to become foragers, they perform learning walks for up to threedays to learn the visual panorama and calibrate their compass systems.7,8 The ants repeatedly stop their forward movement during learning walks for performing turns (pirouettes), interrupted by stopping phases. Gaze directions during the longest stopping phases are directed toward the nest entrance.9 We experimentally manipulated look-back behavior systematically by altering polarity or inclination of the GMF. We demonstrate that Cataglyphis ants, contrary to most other insects studied,10 possess a polarity-sensitive magnetic compass, making them ideal experimental models for narrowing down the evidence for particle-based mechanisms underlying magnetosensation in this insect.

Investigating Differences in the Palomar-Green Blazar Population Using Polarization

We present polarization images with the Karl G. Jansky Very Large Array (VLA) in A- and B-array configurations at 6 GHz of seven radio-loud (RL) quasars and eight BL Lac objects belonging to the Palomar-Green (PG) “blazar” sample. This completes our arcsecond-scale polarization study of an optically selected volume-limited blazar sample comprising 16 radio-loud quasars and 8 BL Lac objects. Using the VLA, we identify kiloparsec-scale polarization in the cores and jets/lobes of all the blazars, with fractional polarization varying from around 0.8% ± 0.3% to 37% ± 6%. The kiloparsec-scale jets in PG RL quasars are typically aligned along their parsec-scale jets and show apparent magnetic fields parallel to jet directions in their jets/cores and magnetic field compression in their hot spots. The quasars show evidence of interaction with their environment as well as restarted active galactic nucleus activity through morphology, polarization, and spectral indices. These quasi-periodic jet modulations and restarted activity may be indicative of an unstable accretion disk undergoing transition. We find that the polarization characteristics of the BL Lacs are consistent with their jets being reoriented multiple times, with no correlation between their core apparent magnetic field orientations and parsec-scale jet directions. We find that the low synchrotron peaked BL Lacs show polarization and radio morphology features typical of “strong” jet sources as defined by E. T. Meyer et al. for the “blazar envelope scenario,” which posits a division based on jet profiles and velocity gradients rather than total jet power.

Intelligent optimization of thermal performance in nanoparticle-enhanced enclosures with sinusoidal heating and magnetic field interaction using Multi Expression Programming

This study advances a comprehensive numerical analysis aimed at enhancing thermal transfer within square enclosures filled with water-based oxide nanoparticle suspensions subjected to central sinusoidal heating. Central to this research is the integration of Multi Expression Programming (MEP) for the predictive optimization of thermal efficiency, taking into account the intricate effects of sinusoidal heating geometry, nanoparticles concentration, and an inclined magnetic field. The analysis maintains the initial setup boundary conditions: no-slip at the enclosure walls, isothermal conditions at the left and right walls, and adiabatic conditions at the top and bottom walls, except where sinusoidal heating is applied. Using MEP, these conditions are explored to identify configurations that significantly enhance thermal performance. This method allows for a detailed examination of the impacts of heating element undulation, magnetic field orientation, and nanoparticle dispersion on flow dynamics and thermal transmission. The results emphasize the significant impact of heating element undulation on the heat transfer rate, with MEP predicting optimal undulations that boost thermal efficiency. Furthermore, the strategic application of magnetic fields, as optimized through MEP, facilitates controlled flow distribution and buoyancy effects, with an increased Rayleigh number leading to enhanced convection patterns. The study also delineates the specific boundary conditions under which the Nusselt number, indicative of thermal performance, increases. These MEP-driven insights are invaluable for designing optimized heat transfer systems and energy-efficient applications, establishing a new benchmark for thermal management strategies in practical engineering contexts, firmly rooted in the precision afforded by computational optimization and predictive modeling.

Investigating the correlation between the magnetic field orientation and molecular outflow direction in some molecular clouds

ABSTRACT This study examines the relationship between the magnetic field orientation of a molecular cloud and its outflow axis, using data from 22 molecular clouds. We find that the position angles of the outflow axis ($\theta _{\text{out}}$) and the cloud-scale magnetic field in the core, measured in the submillimetre region ($\theta _B^{\text{sub}}$), are correlated to each other irrespective of the alignment or misalignment between the two axes. However, it is important to note that these observed position angles are projections on to the plane of the sky. To assess the statistical significance of our findings, we conduct a statistical test to account for the projection effect and find minimal impact. Moreover, we identify a possible role of the Galactic magnetic field orientation ($\theta _{\text{GP}}$) in determining the outflow direction by assessing the offset ($\theta _{\text{off}} = \theta _B - \theta _{\text{GP}}$) in both the core and envelope regions. Furthermore, we explore the influence of parameters such as magnetic field strength (B), the position angle of the minor axis of the cloud cores ($\theta _{\text{min}}$), the inclination angle of the outflow ($i_{\text{out}}$), and other factors on the alignment between the outflow and cloud-scale magnetic field axes ($|\theta _{\text{OB}}| = |\theta _{\text{out}} - \theta _B^{\text{sub}}|$). Our analysis suggests that the orientation of the outflow axis is determined by the combined influence of the magnetic field orientation, the minor axis, the inclination angle of the outflow, and the associated magnetic field strength.

Effectively tuning the quantum Griffiths phase by controllable quantum fluctuations.

Quantum Griffiths phase (QGP), marked by a quantum Griffiths singularity with a divergent effective critical exponent, has garnered considerable attention in the realm of superconductivity. However, the ability to control QGP remains elusive. Here, we demonstrate that QGP at the LaAlO3/KTaO3(110) interface can be efficiently modulated by the orientation of applied magnetic field: With a perpendicular field, an anomalous QGP emerges in the low-temperature regime, characterized by a decreasing critical field as temperature lowers; conversely, with a parallel field, a normal QGP arises, where the critical field increases with decreasing temperature. Such opposite characteristics stem from the controllable quantum fluctuations and conductivity corrections under distinct magnetic field orientations. Furthermore, we show the effective tuning of the phase boundary by electrostatic gating, attributed to the gate-controlled quantum fluctuations. These findings not only demonstrate how to experimentally manipulate QGP but also provide a comprehensive understanding of how quantum fluctuations can effectively modulate QGP.

The Magnetic Field in Quiescent Star-forming Filament G16.96+0.27

We present 850 μm thermal dust polarization observations with a resolution of 14.″4 (∼0.13 pc) toward an infrared dark cloud G16.96+0.27 using James Clerk Maxwell Telescope/POL-2. The average magnetic field orientation, which roughly agrees with the larger-scale magnetic field orientation traced by the Planck 353 GHz data, is approximately perpendicular to the filament structure. The estimated plane-of-sky magnetic field strength is ∼96 μG and ∼60 μG using two variants of the Davis–Chandrasekhar–Fermi methods. We calculate the virial and magnetic critical parameters to evaluate the relative importance of gravity, the magnetic field, and turbulence. The magnetic field and turbulence are both weaker than gravity, but magnetic fields and turbulence together are equal to gravity, suggesting that G16.96+0.27 is in a quasi-equilibrium state. The alignment between the magnetic field and cloud is found to have a trend moving away from perpendicularity in the dense regions, which may serve as a tracer of potential fragmentation in such quiescent filaments.

Applying the Velocity Gradient Technique in NGC 1333: Comparison with Dust Polarization Observations

Magnetic fields (B-fields) are ubiquitous in the interstellar medium (ISM), and they play an essential role in the formation of molecular clouds and subsequent star formation. However, B-fields in interstellar environments remain challenging to measure, and their properties typically need to be inferred from dust polarization observations over multiple physical scales. In this work, we seek to use a recently proposed approach called the velocity gradient technique (VGT) to study B-fields in star-forming regions and compare the results with dust polarization observations in different wavelengths. The VGT is based on the anisotropic properties of eddies in magnetized turbulence to derive B-field properties in the ISM. We investigate that this technique is synergistic with dust polarimetry when applied to a turbulent diffused medium for the purpose of measuring its magnetization. Specifically, we use the VGT on molecular line data toward the NGC 1333 star-forming region (12CO, 13CO, C18O, and N2H+), and we compare the derived B-field properties with those inferred from 214 and 850 μm dust polarization observations of the region using Stratospheric Observatory for Infrared Astronomy/High-Resolution Airborne Wide-band Camera Plus and James Clerk Maxwell Telescope/POL-2, respectively. We estimate both the inclination angle and the 3D Alfvénic Mach number M A from the molecular line gradients. Crucially, testing this technique on gravitationally bound, dynamic, and turbulent regions, and comparing the results with those obtained from polarization observations at different wavelengths, such as the plane-of-sky field orientation, is an important test on the applicability of the VGT in various density regimes of the ISM. We in general do not find a close correlation between the velocity gradient inferred orientations and the dust inferred magnetic field orientations.

Interlaminar fracture toughness and impact resistance of carbon fiber reinforced composite with magnetic aligned CNTs

This study draws inspiration from Z-pins employed in fiber composites. Carbon fiber reinforced polymer (CFRP) laminates modified with Z-oriented carbon nanotubes (Z-CNTs) were fabricated utilizing a magnetic field orientation technique. The interlaminar fracture toughness, impact resistance and damage tolerance of CFRP modified with Z-CNTs were evaluated through end-notched flexure (ENF), low-velocity impact (LVI) tests, and compression after impact (CAI) testing. The enhancement mechanisms were investigated using multiscale techniques, including digital image correlation (DIC), scanning electron microscopy (SEM), molecular dynamics (MD), and finite element (FE) simulations. CFRP modified with 0.3 wt% CNTs showed optimum interlaminar fracture toughness, which improved by 62.9 % in CNT-random samples compared to non-modified samples and further enhanced by 95.2 % in CNT-oriented samples. The DIC and SEM analysis revealed the enhancement mechanism of Z-CNTs in fracture toughness, including (1) enlarging the toughness deformation of resin; (2) broadening the fracture process zone to dissipate the energy; and (3) shifting the failure mode of CNTs from pull-out dominance to fracture dominance. Furthermore, MD simulations showed that the crack propagation location significantly influences the different enhancement mechanisms exhibited by CNTs, which was accord with SEM observations. LVI and CAI tests indicated that specimens modified with Z-CNTs exhibit greater impact resistance and damage tolerance. FE simulation revealed that the mode II interlaminar fracture toughness plays a dominant role in the impact resistance of the laminate. These findings provide an effective strategy and theoretical supports for the design of impact resistance of composite laminates.

Anomalous Josephson effect in altermagnet

Abstract Anomalous Josephson current in an s-wave superconductor junction is due to the parity and time reversal symmetry breaking from the spin-orbit coupling (SOC) together with magnetization. Altermagnetism is an emerging magnetic phase with the d-wave type magnetism but zero macroscopic magnetization. Here, we numerically study the Josephson supercurrent in a two-dimensional junction with both the SOC and altermagnetism. It is found that the $0$-$\pi$ transition can appear in the system by modulating the junction's lengths or the SOC strengths despite the zero net magnetization in the system. An anomalous Josephson effect is also identified but dependent on the orientation of magnetization.

Comparison of Commercial REBCO Tapes Through Flux Pinning Energy

This work presents a comparison of different commercial tapes belonging to the second-generation High-Temperature Superconductors (2G HTS) produced by SuNAM Co., Ltd., SuperOx, and Shanghai Superconductors Technology Co., Ltd. (SST) companies. The aim is to investigate pinning mechanisms responsible for best performances, looking at the anisotropy of the irreversibility field and of the flux pinning energy. The irreversibility line states the upper limit of current-carrying capacity, whereas the flux pinning energy explores the ability of material defects to act as weak collectively or strong single vortex pinning centers. All investigated samples have artificial pinning centers (APCs) included in the superconducting matrix: BHO-doped EuBCO for SST, Y2O3 in YBCO for SuperOx, and Gd2O3 particles trapped in GdBCO for SuNAM. Resistive transition curves were measured in high magnetic fields up to 16 T for magnetic field orientations parallel and perpendicular to the tape surface. We found that the anistropy of SST tape shows an overall independence both on temperature and magnetic field, while the other two samples show a more complex behavior. This leads to the conclusion that properly engineered APC optimization in coated conductors can further reduce anisotropy of superconducting properties.