Magnetic Axis Research Articles

Energy-resolved pulse profile changes in V 0332+53: Indications of wings in the cyclotron absorption line profile

We aim to investigate the energy-resolved pulse profile changes of the accreting X-ray pulsar focusing in the cyclotron line energy range, using the full set of available observations. We applied a tailored pipeline to study the energy dependence of the pulse profiles and to build the pulsed fraction spectra (PFS) for the different observations. We also studied the profile changes using cross-correlation and lag spectra. We re-analysed the energy spectra to search for links between the local features observed in the PFS and spectral emission components associated with the shape of the fundamental cyclotron line. In the PFS data, with sufficiently high statistics, we observe a consistent behaviour around the cyclotron line energy. Specifically, two Gaussian-shaped features appear symmetrically on either side of the putative cyclotron line. These features exhibit minimal variation with source luminosity, and their peak positions consistently remain on the left and right of the cyclotron line energy. Associated with the cyclotron line-forming region, we interpret them as evidence for the resonant cyclotron absorption line wings, as predicted by theoretical models of how the cyclotron line profile should appear along the observer's line of sight. A phase-resolved analysis of the pulse in the energy bands surrounding these features enables us to determine both the spectral shape and the intensity of the photons responsible for these peaks in the PFS. Assuming these features correspond to a spectral component, we used their shapes as priors for the corresponding emission components, finding a statistically satisfactory description of the spectra. To explain these results, we propose that our line of sight is close to the direction of the spin axis, while the magnetic axis is likely orthogonal to it.

Guanine-based spin valve with spin rectification effect for an artificial memory element.

Non-volatile electronic memory elements are very attractive for applications, not only for information storage but also in logic circuits, sensing devices and neuromorphic computing. Here, a ferroelectric film of guanine nucleobase is used in a resistive memory junction sandwiched between two different ferromagnetic films of Co and CoCr alloys. The magnetic films have an in-plane easy axis of magnetization and different coercive fields whereas the guanine film ensures a very long spin transport length, at 100K. The non-volatile resistance states of the multiferroic spintronic junction with two-terminals are manipulated by a combined action of small external magnetic and electric fields. Thus, the magnetic field controls the relative orientation of the magnetization of the metallic ferromagnetic electrodes, that leads to different magnetoresistance states. The orientation and the magnitude of the electric field controls the orientation of the polarization of the guanine ferroelectric barrier, that leads to different electroresistance states, respectively. Moreover, we have observed a strong interfacial coupling of the two parameters. Consequently, positive and negative magnetoresistance hysteresis loops corresponding to spin rectification effects and non-hysteretic (erased) resistive states are manipulated with the electric field by switching the orientation of the electrical polarization of the organic ferroelectric.

Manipulating the electronic and magnetic properties by ferroelectric polarization switching in 2D NiCl2/Ga2S3 van der Waals heterostructure

Exploring magnetoelectric coupling properties in multiferroic materials is scientifically intriguing and of great technical importance in nanoscale devices. In this work, the magnetoelectric coupling behaviors in the two-dimensional (2D) multiferroic heterostructure (HS), NiCl2/Ga2S3, are explored using density functional theory calculations. Our results show that the NiCl2/Ga2S3 HS remains in the ferromagnetic (FM) state in both ferroelectric (FE) polarization states, with the magnetic easy axis lying close to the xoz plane in the Ga2S3-P↓ state and aligning along the eclipsed z axis in the Ga2S3-P↑ state, respectively. Moreover, the HS in the Ga2S3-P↑ polarization state behaves as an FM semiconductor, while it changes to be an FM half-metal in the Ga2S3-P↓ polarization state. By applying tensile strains, the NiCl2/Ga2S3-P↓ can transit from FM quasi-half-metal to FM semiconductor with type-II band alignment. The regulation of physical properties that is induced by the FE layer in the HS originates from interfacial charge transfer due to the proximity effect. This work offers a platform to fabricate a magnetoelectric coupling interaction in 2D multiferroic devices.

Ferroelectric polarizations engineered reversible skyrmion–bimeron switch in van der Waals heterostructure RuClBr/Ga2S3

Controllable operation between different magnetic topological states, such as skyrmions and bimerons, which share the same topological charge but exhibit distinct properties, has garnered extensive attention due to their potential applications in future high-density memory technologies. However, their remarkable origin mechanisms (e.g., in-plane and out-of-plane easy magnetic axis) make effective control of their switching a huge challenge. Based on first-principles calculations, we explore the 2D RuClBr/Ga2S3 van der Waals heterostructure and find that the skyrmion and bimeron topological states could be switched instantaneously and efficiently by regulating the electric polarization of Ga2S3 with an external electric field. Additionally, atomic spin dynamic simulations reveal that the evolved skyrmion and bimeron magnetic configurations are highly resistant to external disturbances, enduring external magnetic fields of up to 20 T. This efficient transformation between magnetic states is driven by magnetic anisotropy accompanying changes in the polarization state. Our work predicts that the RuClBr/Ga2S3 system is an ideal platform for addressing this control problem.

Comparison and design of the transverse flux motor with axial and radial permanent magnet for electrical propulsion system

Comparison and design of the transverse flux motor with axial and radial permanent magnet for electrical propulsion system

Modulation of the Magnetic Anisotropy via the Ligand Field in Sandwiched Erbium Complexes.

Among lanthanide-based single-molecule magnets (SMMs), erbium(III) is a Kramers ion, apart from dysprosium(III), which provides magnetic bistability in the presence of a suitable coordination environment. However, Er-based SMMs exhibit significantly less magnetic anisotropy than Dy because their prolate electronic density necessitates equatorially correlated ligands to minimize the charge contact with the Er atom. Here, in this work, we have computationally investigated the heteroleptic organometallic complexes with an Er(III) atom sandwiched between two distinct cyclic rings (five- and eight-membered) with the aim of tuning the magnetic anisotropy via exploiting the ligand field. The ligand field is manipulated by substituting one of the C atoms from the five-membered ring with heteroatoms (groups 14 and 15), while the other (eight-membered) ring remains intact. The electronic and magnetic properties have been investigated using first-principles-based ab initio approaches. The distortion in the planarity of the five-membered ring generated by the larger heteroatom affects the bonding with magnetic Er and consequently the electronic structure. This is observed to modify the ligand field and the magnetic axis, thereby improving the magnetic relaxation barrier.

A mechanism of magnetic hysteresis in heterogeneous Gd-Zr-Co-Cu-Fe alloys

The behavior of the (Gd, Zr)(CoCuFe)Z alloys samples in magnetic fields oriented at different angles to their easy magnetization axis has been studied. The angular dependences of magnetization and coercivity were constructed. The hysteresis loops of the two main structural components of the samples were constructed based on images of the domain structure in demagnetizing fields. An analysis of the obtained results was carried out under assumption of the mixed mechanism of hysteresis in these alloy family.

Search for interpulses in a complete sample of pulsars at a frequency of 111 MHz

An interpulse search was carried out in a sample of 96 pulsars observed on the Large Phased Array (LPA) radio telescope in the Pushchino Multibeams Pulsar Search (PUMPS). The pulsar sample is complete for pulsars having a signal-to-noise ratio (S/N) in the main pulse (MP) greater than 40. To search for weak interpulses (IP), the addition of average profiles over an interval of up to 10 years was used. Interpulses were detected in 12 pulsars (12.5% of the sample), of which 7 pulsars have an interpulse located near the 180◦ phase relative to the main pulse (probable orthogonal rotators), and 5 have phases far from 180◦ (probable coaxial rotators). The amplitude ratios of IP/MP are in the range of 0.004−0.023, the median value is 0.01. Estimates of the observed number of coaxial and orthogonal rotators with IP/MP ≥0.01 do not contradict the model according to which, during evolution, the magnetic axis and the axis of rotation become orthogonal.

Improved pulse high frequency voltage injection method based low-speed sensorless control of axial field flux-switching permanent magnet motors

Improved pulse high frequency voltage injection method based low-speed sensorless control of axial field flux-switching permanent magnet motors

Observation of bi-directional global Alfvén eigenmodes in the MAST-U tokamak

Abstract The first observations and classification of deuterium beam-driven sub-cyclotron frequency range Alfvén eigenmodes (AEs) are presented for the MAST-Upgrade tokamak. Sets of observed eigenmodes are separated in frequency by approximately 200 kHz. We observe a lower frequency separation of ∼10 kHz within each set, and the toroidal mode number n increases with frequency sequentially. The ∼200 kHz step between the sets coincides with the interval between successive curves of the Shear Alfvén continuum according to linear ideal MHD modeling. The sub-cyclotron frequency AEs can be identified as the global AEs (GAEs) localized at the continuum extrema regions. Each set contains the same range of n. These observations are consistent with our GAE modeling. In low plasma current (I p) discharges, we observe only GAEs propagating counter to the plasma current and the beam direction. These GAEs are located near the magnetic axis. We observe counter and co-propagating GAEs simultaneously in higher I p discharges. The co-propagating GAEs occur because of the formation of second continuum minima. Very flat safety factor profiles in higher I p MAST-U discharges give rise to these minima. They are located at around half of the plasma radius. The GAEs have properties that are very different to those of compressional AEs previously reported for the MAST tokamak with low magnetic fields (Sharapov et al 2014 Phys. Plasmas 21 082501) before the upgrade.

Experimental investigation of the radial structure of energetic particle driven GAM in TCV

Abstract High amplitude energetic particle geodesic acoustic mode (EGAM) oscillations driven by Neutral Beam (NBI) injected in the direction counter to the toroidal plasma current are observed in the TCV tokamak. The modes appear at frequencies close to the geodesic acoustic mode (GAM) frequency, corresponding to the mode radii calculated without plasma elongation corrections. The spatial structure of the EGAM density oscillation is analyzed using multichannel soft x-ray (SXR) and broadband light emission diagnostics. The analysis of spatiotemporal emission data shows a non-rotating structure of the density oscillations. The non-rotating mode discrimination is the additional new capability of the multichannel spatiotemporal SXR data analysis technique in TCV. We present the discrimination method of assessing the standing character of the EGAM wave. The structure of EGAM density oscillations in TCV is consistent with the theoretical GAM poloidal structure, namely a m= 1 standing wave with density oscillations amplitude proportional to sin(θ), where the poloidal angle θ is measured from the equatorial plane. The poloidal structure of magnetic the field oscillations is analyzed using a poloidal array of magnetic coils. The structure of the EGAM-induced magnetic field oscillations in TCV is a m = 2 standing wave. Time evolution of EGAMs suggests that a nonlinear EGAM chirping is observed. The chirping depends on the EGAM radial location, which varies as the NBI deposition is varied through a vertical shift of the plasma magnetic axis. The chirping disappears at the plasma periphery. A fast periodic radial shift of the EGAMs radial location is also observed to occur during the single chirp.

Enhanced perpendicular magnetic anisotropy energy and Curie temperature in the CrOCl monolayer: strain effects

Abstract Magnetic monolayers offer a wide variety of applications in enhancing the functionalities of storage devices including higher thermal stability, lower power consumption, and higher operation speed, owing to their intrinsic long-range spin ordering. Herein, we study the biaxial ([110]) strain range of ± 5% influence on the formation energetics, electronic structure, and magnetic behaviour of the CrOCl monolayer (ML) based on the ab-initio calculations including spin–orbit coupling (SOC) effects. It is predicted that the system displays an insulating character having an energy band gap (E g ) of 2.05 eV with a ferromagnetic (FM) ground state in its unstrained state. The estimated partial spin magnetic moment on the Cr ion is +2.7 μ B /f.u. (per formula unit) with S = 1.5 and lies in a + 3 oxidation state with an electronic distribution of t 2 g 3 ↑ t 2 g 0 ↓ e g 0 ↑ e g 0 ↓ . Along with this, [001] (c-axis) is found to be the easy magnetic axis, which results in a magnetic anisotropy energy (MAE) of 0.2 meV having an MAE constant of 0.25 mJ m−2 and the computed Curie temperature (T c ) using Ising model is 157 K. Furthermore, the system shows the robustness of the FM insulating behavior against considered strains. However, a significant shift in the conduction band edge (CBE) position to lower energies is evident for tensile strains, which substantially reduces the E g up to 13%. The decrease in E g value is evidence of higher absorption in the visible range which makes it the best option for optoelectronics and photocatalysis. Simultaneously, our results revealed that strain enhances the MAE and T c up to 190% and 43%, respectively. Hence, optimized E g , MAE, and T c within a considerable strain range, make the CrOCl ML a potential candidate for its utilization in magnetic memory devices.

Unravelling sub-stellar magnetospheres

At the sub-stellar boundary, signatures of magnetic fields begin to manifest at radio wavelengths, analogous to the auroral emission of the magnetised solar system planets. This emission provides a singular avenue for measuring magnetic fields at planetary scales in extrasolar systems. So far, exoplanets have eluded detection at radio wavelengths. However, ultracool dwarfs (UCDs), their higher mass counterparts, have been detected for over two decades in the radio. Given their similar characteristics to massive exoplanets, UCDs are ideal targets to bridge our understanding of magnetic field generation from stars to planets. In this work, we develop a new tomographic technique for inverting both the viewing angle and large-scale magnetic field structure of UCDs from observations of coherent radio bursts. We apply our methodology to the nearby T8 dwarf WISE J062309.94-045624.6 (J0623) which was recently detected at radio wavelengths, and show that it is likely viewed pole-on. We also find that J0623’s rotation and magnetic axes are misaligned significantly, reminiscent of Uranus and Neptune, and show that it may be undergoing a magnetic cycle with a period exceeding 6 months in duration. These findings demonstrate that our method is a robust new tool for studying magnetic fields on planetary-mass objects. With the advent of next-generation low-frequency radio facilities, the methods presented here could facilitate the characterisation of exoplanetary magnetospheres for the first time.

Two dimensional MoF3 and Janus Mo2F3X3(X = Cl, Br, I): intrinsic ferromagnetic semiconductor, large perpendicular magnetic anisotropy, and hole-induced room-temperature ferromagnetism

Abstract Two-dimensional (2D) ferromagnetic (FM) semiconductors with high Curie temperature (T c ) and large perpendicular magnetic anisotropy (PMA) are promising for developing next-generation magnetic storage devices. In this work, we investigated the structural, electronic, and magnetic properties of MoF3 and Janus Mo2F3 X 3 (X = Cl, Br, I) monolayers by first-principles methods. These materials are 2D FM semiconductors with large PMA and half-semiconducting character as both VBM and CBM belonging to the spin-up channel. Biaxial strain can modulate band gap, reverse easy magnetization axis, and induce magnetic phase transitions in MoF3 monolayer and its Janus structures. Compared to MoF3 monolayers, Janus Mo2F3 X 3 monolayers can preserve the structural ability and the FM ground state over a wider range of strain. The magnetic anisotropy energies (MAEs) of these 2D materials can be enhanced to greater than 1 meV/Mo by tensile strains. Intrinsic T c of MoF3 monolayer and its Janus structures are less than 110 K and are insensitive to strain. However, hole doping with a feasible concentration can achieve a room-temperature half-metallicity in these 2D materials. The required hole concentration is lower in Janus Mo2F3 X 3 monolayers than MoF3 monolayer. Our results indicate that MoF3 and Janus Mo2F3 X 3 (X = Cl, Br, I) monolayers are promising candidates for 2D spintronic applications and will stimulate experimental and theoretical broad studies.

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.

Magnetic properties of the RNiIn4 (R = Ce, Pr, Nd) series of intermetallic compounds grown by the metallic flux method

This work focuses on the synthesis, structural and magnetic characterization, and the effects of the Crystal Electric Field (CEF) of RNiIn4 (R = Ce, Pr, Nd) compounds. By using the metal flux technique, high-quality single crystals were obtained and analyzed X-ray diffraction and confirmed the formation of a single phase for all compounds and revealed their crystallization in a orthorhombic structure. Magnetic susceptibility measurements revealed antiferromagnetic in order ing temperatures (TN) at 4.02 K, 2.37 K and 4.06 for Ce, Pr, and Nd, respectively. Specific heat data corroborated these findings. The results indicate the easy axis of magnetization lies in the ab-plane for Ce and Nd, and along the c-axis for Pr.

Research on magnetic force of magnetic seal in aero-engine

Aiming at the magnetic seal in an aero-engine accessory, the range of magnetic force required for the normal operation of the magnetic seal is analyzed. The finite element analysis method based on the Maxwell stress tensor method is used to calculate the magnetic force between the dynamic ring and the magnetic static ring in the magnetic sealing system. The magnetic force under different magnetization modes and gaps is tested by the magnetic measuring test bench, which verifies the correctness of the magnetic calculation method. The effects of permanent magnet material, permanent magnet magnetization direction, magnetic seal structural parameters, and working conditions on the magnetic force between the dynamic ring/magnetic static ring in the magnetic seal are analyzed. Under the same structure, the magnetic force of NeFeB35, SmCo28, Alnico5, and Ferrite as magnetic static rings is compared. The results show that NdFeB35 has the largest magnetic force, SmCo28 is second, Alnico5 and Ferrite are relatively small, and their magnetic forces are about 1/4 to 1/5 of the first two materials. When the rotor or the casing is moving axially, NeFeB35 and SmCo28 materials with large magnetic force should be selected to meet the normal working requirements. Under the same material, the magnetic forces of axial, radial, and radiative magnetization modes are compared. the ratio of magnetic force under axial, radiative, and radial magnetization is about 2.3:1.1:1. If NeFeB35 and SmCo28 materials are axially magnetized, their magnetic forces will exceed the allowable range, which will increase the seal wear. The increase in the inner diameter of the dynamic ring and the gap between the dynamic ring and the magnetic static ring causes a decrease in the magnetic force. The increase in temperature affects the magnetic properties of permanent magnetic material, which leads to the decline of magnetic force between the dynamic ring and the magnetic static ring. The increase in rotor speed leads to the acceleration of the fluctuation frequency of the magnetic force. Still, the maximum and minimum values of the magnetic force under different speeds remain unchanged, and the maximum fluctuation rate is less than 3%. According to the analysis results, the fitting formula of magnetic force calculation is presented by the orthogonal test and the least squares method.

Thin Films of BaM Hexaferrite with an Inclined Orientation of the Easy Magnetization Axis: Crystal Structure and Magnetic Properties.

Thin (~50 nm thick) BaM hexaferrite (BaFe12O19) films were grown on (1-102) and (0001) cut α-Al2O3 (sapphire) substrates via laser molecular beam epitaxy using a one- or two-stage growth protocol. The advantages of a two-stage protocol are shown. The surface morphology, structural and magnetic properties of films were studied using atomic force microscopy, reflected high-energy electron diffraction, three-dimensional X-ray diffraction reciprocal space mapping, powder X-ray diffraction, magneto-optical, and magnetometric methods. Annealed BaFe12O19/Al2O3 (1-102) structures consist of close-packed islands epitaxially bonded to the substrate. The hexagonal crystallographic axis and the easy axis (EA) of the magnetization of the films are deflected from the normal to the film by an angle of φ~60°. The films exhibit magnetic hysteresis loops for both in-plane Hin-plane and out-of-plane Hout-of-plane magnetic fields. The shape of Mout-of-plane(Hin-plane) and Min-plane(Hin-plane) hysteresis loops strongly depends on the azimuth θ of the Hin plane, confirming the tilted orientation of the EA. The Mout-of-plane(Hout-of-plane) magnetization curves are caused by the reversible rotation of magnetization and irreversible magnetization jumps associated with the appearance and motion of domain walls. In the absence of a magnetic field, the magnetization is oriented at an angle close to φ.

Pulsed and Polarized X‐Ray Emission From Neutron Star Surfaces

ABSTRACTThe intense magnetic fields of neutron stars naturally lead to strong anisotropy and polarization of radiation emanating from their surfaces, both being sensitive to the hot spot position on the surface. Accordingly, pulse phase‐resolved intensities and polarizations depend on the angle between the magnetic and spin axes and the observer's viewing direction. In this paper, results are presented from a Monte Carlo simulation of neutron star atmospheres that uses a complex electric field vector formalism to treat polarized radiative transfer due to magnetic Thomson scattering. General relativistic influences on the propagation of light from the stellar surface to a distant observer are taken into account. The paper outlines a range of theoretical predictions for pulse profiles at different X‐ray energies, focusing on magnetars and also neutron stars of lower magnetization. By comparing these models with observed intensity and polarization pulse profiles for the magnetar 1RXS J1708‐40, and the light curve for the pulsar PSR J0821‐4300, constraints on the stellar geometry angles and the size of putative polar cap hot spots are obtained.

Composite quadrupole order in ferroic and multiferroic materials

The formalism of composite and intertwined orders has been remarkably successful in discussing the complex phase diagrams of strongly correlated materials and high-$T_c$ superconductors. Here, we propose that composite orders are also realized in ferroelectric and ferromagnetic materials when lattice anisotropy is taken into account. This composite order emerges above the ferroic phase transition, and its type is determined by the easy axis of magnetization or polarization, respectively. In multiferroic materials, where polarization and magnetization are coupled, composites of both orders are possible. This formalism of composite orders naturally accounts for magnetoelectric monopole, toroidal, and quadrupole orders. More broadly, composite orders may explain precursor phenomena in incipient (multi)ferroic materials, arising at temperatures above the ferroic phase transition and potentially contributing to the characterization of currently hidden orders.