Magnetic Field Angle Research Articles

Intrinsic mechanism for magnetothermal conductivity oscillations in spin-orbit-coupled nodal superconductors

We describe a mechanism by which the longitudinal thermal conductivity $\kappa_{xx}$, measured in an in-plane magnetic field, oscillates as a function of field angle in layered nodal superconductors. These oscillations occur when the spin-orbit splitting at the nodes is larger than the nodal scattering rate, and are complementary to vortex-induced oscillations identified previously. In sufficiently anisotropic materials, the spin-orbit mechanism may be dominant. As a particular application, we focus on the cuprate high-temperature superconductor YBa$_2$Cu$_3$O$_{6+x}$. This material belongs to the class of Rashba bilayers, in which individual CuO$_2$ layers lack inversion symmetry although the crystal itself is globally centrosymmetric. We show that spin-orbit coupling endows $\kappa_{xx}/T$ with a characteristic dependence on magnetic field angle that should be easily detected experimentally, and argue that for underdoped samples the spin-orbit contribution is larger than the vortex contribution. A key advantage of the magneto-thermal conductivity is that it is a bulk probe of spin-orbit physics, and therefore not sensitive to inversion breaking at surfaces.

Numerical Analysis on Hysteresis Loss of HTS Bitter Magnet

The high temperature superconducting (HTS) Bitter magnet soldered by REBCO annular plates with grooves we proposed recently has the advantage of small size, strong magnetic field, etc. The current distribution of the Bitter magnet can be controlled by adjusting the area of the soldering joint. In this paper, the AC loss of the HTS Bitter magnet during the charging process is numerically analyzed. The results show that the AC loss of the HTS Bitter magnet during a field ramp depends strongly on the magnetic field and the magnetic field angle between the magnetic field and the annular plate thus leading to the maximum AC loss in the regions with the small radius of the HTS Bitter magnet.

A numerical study of the entropy generation and heat transfer rate of airflow around a NACA 0015 airfoil subjected to an external magnetic field

In the present study, the thermal Lattice Boltzmann Technique is combined with the Ghost Fluid method to simulate the flow and heat transfer rate around a NACA 0015 airfoil in the presence of an external magnetic field source. It is tried to investigate the mutual effects of the Hartmann and Reynolds numbers as well as the magnetic field angle and the attack angle of the airfoil on the flow and heat transfer characteristics. Besides, the total entropy generation rate of the system was studied through its main components, i.e. entropy generation rate due to friction, heat transfer, and Magneto Hydrodynamics. Therefore, the tests were carried out for various Re and Ha numbers, plus different magnetic field angles and airfoil attack angles, and their influence on the active parameters which are Cd, Cl, and Nu, along with the entropy generation rate of the system, were recorded. The results revealed that with an increment of the Re number the Cd and Cl graphs drop, but the Nu value raises. Also, the total entropy generation rate of the system is at its maximum around γ = 60.

The influence of magnetic field orientation on metal mixing in electromagnetic stirring enhanced wire feed laser beam welding

The application of the electromagnetic stirring from an oscillating magnetic field can improve the metal mixing in wire feed laser beam welding. However, the extra parameters introduced in this technique make the selection of an optimal combination of process parameters more difficult. In the current study, besides the commonly concerned magnetic flux density and frequency, the influence of the magnetic field orientation (magnetic field angle) on the transport of filler metal is studied numerically and experimentally. Ex-situ X-ray fluorescence spectrometer measurements are used to map the metal mixing in the final weld. A three-dimensional transient multi-physical model is developed to reveal the deeper physical essence, considering the coupling between heat transfer, fluid flow, keyhole dynamics, element transport and magnetohydrodynamics. The spatial distribution of the laser energy on the keyhole wall is calculated by a ray tracing algorithm. The results show that the magnetic field with smaller angle with respect to the transverse direction provides better penetration capacity, and its stirring effect can reach the lower part of the molten pool. Therefore, the smaller magnetic field angle produces better metal mixing. A constant downward flow is formed at the lower part of the molten pool when magnetic field of 10° angle is applied, which brings the filler metal to the root region. As the magnetic field angle increases to 40°, the beneficial downward flow changes into a constant upward flow, resulting in a concentration of the filler metal in the upper region. This study provides further insight of the underlying physics in the electromagnetically enhanced laser beam welding, which may guide the optimization of parameters to achieve property homogeneity or to avoid potential defects.

Single-channel vector magnetic information detection method based on diamond NV color center* *Project supported by the National Natural Science Foundation of China (Grant Nos. 51635011, 51805493, 51775522, 51727808, and 51922009), the Applied Basic Research Program in Shanxi Province, China (Grant No. 201901D111011(ZD)), the Key Research and Development Program in Shanxi Province, China (Grant No. 201803D121067), the Fund from the Key

A method of detecting the single channel triaxial magnetic field information based on diamond nitrogen-vacancy (NV) color center is introduced. Firstly, the incident angle of the bias magnetic field which can achieve the equal frequency difference optically-detected magnetic resonance (ODMR) spectrum of diamond NV color center is calculated theoretically, and the triaxial magnetic information solution model is also constructed. Secondly, the microwave time-controlled circuit module is designed to generate equal timing and equal frequency difference microwave pulse signals in one channel. Combining with the optical detection magnetic resonance technology, the purpose of sequentially locking and detecting the four formant signals on one side of the diamond NV color center (m s = –1 state signal) is achieved, and the vector magnetic field information detection is accomplished by combining the triaxial magnetic information solution model. The system can obtain magnetic field detection in a range of 0 mT–0.82 mT. The system’s magnetic noise sensitivity is 14.2 nT/Hz1/2, and the deviation angle errors of magnetic field detection θx and θy are 1.3° and 8.2° respectively.

Magnetic nanofluid behavior including an immersed rotating conductive cylinder: finite element analysis

In this paper, numerical Galerkin Finite Element Method (GFEM) is applied for conjugate heat-transfer of a rotating cylinder immersed in Fe3O4-water nanofluid under the heat-flux and magnetic field. The outer boundaries of the cavity were maintained at low temperatures while beside the cylinder were insulated. It is assumed that the cylinder rotates in both clockwise and counter-clockwise directions. The dimensionless governing equations such as velocity, pressure, and temperature formulation were analyzed by the GFEM. The results were evaluated using the governing parameters such as nanoparticles (NPs) volume fraction, Hartmann and Rayleigh numbers, magnetic field angle and NPs shapes. As a main result, the average Nusselt number increases by increasing the NPs volume fraction, inclination angle and thermal conductivity ratios, while increasing the Hartmann number decreased the Nusselt number. Furthermore, platelet NPs had the maximum average Nusselt number and spherical NPs made the minimum values of Nusselt numbers among examined NPs shapes.

Nuclear spin assisted magnetic field angle sensing

Quantum sensing exploits the strong sensitivity of quantum systems to measure small external signals. The nitrogen-vacancy (NV) center in diamond is one of the most promising platforms for real-world quantum sensing applications, predominantly used as a magnetometer. However, its magnetic field sensitivity vanishes when a bias magnetic field acts perpendicular to the NV axis. Here, we introduce a different sensing strategy assisted by the nitrogen nuclear spin that uses the entanglement between the electron and nuclear spins to restore the magnetic field sensitivity. This, in turn, allows us to detect small changes in the magnetic field angle relative to the NV axis. Furthermore, based on the same underlying principle, we show that the NV coupling strength to magnetic noise, and hence its coherence time, exhibits a strong asymmetric angle dependence. This allows us to uncover the directional properties of the local magnetic environment and to realize maximal decoupling from anisotropic noise.

Brownian motion of magnetonanofluid flow in an undulated partially heated enclosure

This paper is framed to analyze mixed convection flow features of a CuO - H11H2O2O nanoliquid within a partially heated wavy enclosure. The enclosure is embraced by the inclined magnetic field. In addition, the impact of Brownian motion is assimilated into the nanoliquid. Two models, namely the viscosity and the thermal conductivity depending on the Brownian motion of nanoliquid are used. The numerical solutions of the control equations constituting Navier-Stokes equations are carried out by adopting a compact finite difference scheme. Our computed results using some experimental data are compared to the results available in the literature and a nice resemblance is obtained. Numerical results for the specified problem are investigated by controlling the key characteristics such as nanoparticle concentration (0≤ϕ≤0.04), Richardson number (0.1≤Ri≤20), Reynolds number (50≤Re<750), Grashof number (Gr=5×104), Hartmann number (0≤Ha≤60), orientation angle of magnetic field (00≤γ≤900), number of undulations (0≤λ≤3) and amplitude of wavy surface (A=0.05). It is established that the angle γ and the position of the heating area play a crucial role in the liquid motion and heat transport inside the wavy cavity. The energy transfer rate can be augmented or diminished in presence of nanoparticles along with variations of Hartmann and Richardson numbers as well as the number of waviness of the bottom surface of the enclosure.

Quantifying Global and Random Uncertainties in High Resolution Global Geomagnetic Field Models Used for Directional Drilling

SummaryTotal field strength, declination, and dip angle of the Earth's magnetic field, in conjunction with gravity, are used by magnetic-survey tools to determine a wellbore's location. Magnetic field values may be obtained from global models that, depending on the model, have a wide range of spatial resolution at the Earth's surface from large scale (3000 km) to small scale (28 km). The magnetic field varies continuously in both time and space, so no model can fully capture the complexity of all sources; hence, there are uncertainties associated with the values provided. The SPE Wellbore Positioning Technical Section/Industry Steering Committee on Wellbore Surveying Accuracy (ISCWSA) published their original measurement-while-drilling (MWD) error model in 2000. Such models and uncertainties define positional error ellipsoids along the wellbore, which assist the driller in achieving their geological target, in addition to aiding collision avoidance. With the recent update to Revision 5 of the ISCWSA error model, we have reassessed the uncertainties associated with our latest high-resolution global magnetic field model.We describe the derivation of location-specific global and random uncertainties for use with predicted geomagnetic values from high-resolution models within magnetic MWD survey-tool-error models. We propose a sophisticated approach to provide realistic values at different locations around the globe; for example, we determine separate errors for regions where the models have high spatial resolution from aeromagnetic data compared to regions where only satellite data are available.The combined uncertainties are freely available via a web service with which the user can also see how they vary with time. The use of the revised uncertainty values in the MWD-error model, in most cases, reduces the positional error ellipsoids and allows better use of the increased accuracy from recent improvements in geomagnetic modeling. This is demonstrated using the new uncertainty values in the MWD-error model for three standard ISCWSA well profiles. A fourth theoretical well offshore Brazil where the vertical magnetic field is weak shows that with drillstring interference correction relying on the more uncertain magnetic dip, the positional error ellipsoids can increase. This is clearly of concern for attaining geological targets and collision avoidance.

Three-Dimensional (3D) Visualization and Two-Dimensional (2D) Second Law Analysis of Magnetohydrodynamic (MHD) Free Convection Inside Cubical Enclosure Packed with Hybrid Nanofluid Containing a Circular Heating Cylinder: Effect of Inclined Magnetic Field

In the present work, an irreversibility analysis of three- (3D) and two-dimensional (2D) magnetohydrodynamic (MHD) free convection inside cubical enclosure packed with hybrid water nanofluid (alumina, titanium dioxide and copper) is carried out. The discretization of the momentum and energy equations is done by employment of finite volume approach with SIMPLE algorithm. The effect of inclined magnetic on the heat transfer rate and various entropy types is investigated. All numerical tests are obtained for various Rayleigh numbers 103 ≤ Ra ≤ 106, Hartman numbers 0 ≤ Ha ≤ 45, hybrid nanoparticles percentage 0 ≤ φ % ≤ 5%, and the magnetic field angle 0 ≤ α≤90°. The Bejan number is used in this study to show the entropy type dominant. The first part of this study is about showing a three-dimensional shape of the particles trajectory, isotherms, local Bejan number and different local entropy types; then the second part is limited to a two-dimensional study of all physical quantities. As main results, it is demonstrated that the rate of heat transfer and entropy creation are significantly improved by changing the Rayleigh number, Hartmann number and the magnetic field angle. Moreover, it is also found that the effect of increasing the volume fraction of hybrid nanoparticles can be optimized to get good enhancement of heat transfer rate.

Research on current carrying capacity of Bi-2223/Ag superconducting tape in the temperature range of 75–105 K

In order to study the feasibility of the co-transmission of electricity and liquefied natural gas (LNG) based energy fluid, we carried out a project supported by a grant from Chinese national key research and development program, Basic Research on Superconducting DC Energy Pipeline. In this project, a superconducting cable cooled by LNG based mixed energy fluid at temperature around 90 K is proposed. As the first commercial high-temperature superconducting wire, the silver-sheathed (Bi, Pb)2Sr2Ca2Cu3O10 tape is the only choice for the conductors of superconducting cable in this project due to its superiorities such as high critical temperature and high cost performance. Current carrying capacity is one of the important properties for applications of practical superconductors. However, there has been no systematic data on the current carrying capacity and characteristic of this kind of HTS wire above liquid nitrogen temperature available in literature up to date. In this study, we systematically measured the critical current of Bi-2223/Ag tape samples in a temperature range of 75–105 K, at different magnetic field and field angles. In this paper, experimental details and measurement results are reported. Some practical suggestions are proposed for the applications of this kind of HTS wire in this temperature region. The experimental results obtained in this study will make up the lack of the critical current data of Bi-2223/Ag tape above liquid nitrogen temperature in literature, and provide some fundamental information for the applications of Bi-2223/Ag tape in this temperature region.

Characteristics of non-Maxwellian magnetized sheath with secondary electron emission

In this paper, the effects of non-Maxwellian distribution of electrons on the characteristics of magnetized plasma sheath with secondary electron emission are investigated by using a magnetic fluid model of one-dimensional velocity and three-dimensional space. The velocity of electrons follows the non-extensive distribution, and the ions are magnetized in a magnetic field with a certain tilt angle relative to the wall. The effects of the non-extensive electron distribution parameter &lt;i&gt;q&lt;/i&gt; and the magnetic field strength and angle on the Bohm criterion, the floating wall potential, the secondary electron number density at the sheath edge, the sheath thickness and the ion velocity are studied by establishing the self-consistent equations. When the electron velocity distribution deviates from the Maxwellian distribution, the results show that as the &lt;i&gt;q&lt;/i&gt;-parameter increases, the value of the Bohm criterion decreases, the floating wall potential increases, the number of secondary electrons at the sheath increases, the sheath thickness decreases, the number density of ions and electrons decline faster, the number density of ions near the wall is higher, and the velocities of the ions in the three directions are all reduced. In addition, as the magnetic field strength increases, the sheath thickness decreases, and the number density of ions and electrons in the sheath area decrease rapidly; the larger the magnetic field angle, the more significant the influences of the parameter &lt;i&gt;q&lt;/i&gt; on the wall potential and the sheath thickness are, while the velocity component of the ion in the &lt;i&gt;x&lt;/i&gt;-direction decreases with the increase of the magnetic field angle, but in the case of super-extensive distribution (&lt;i&gt;q&lt;/i&gt; &lt; 1), the velocity change near the wall presents an opposite trend, the increase of magnetic field angle causes wall velocity to increase; when it is close to Maxwellian distribution (&lt;i&gt;q&lt;/i&gt; → 1), the velocity near the wall does not depend on the change of the magnetic field angle and basically tends to be identical; in the case of sub-extensive distribution (&lt;i&gt;q&lt;/i&gt; &gt; 1), the velocity near the wall decreases with the magnetic field angle increasing.

Effects of magnetic field inclination and internal heat sources on nanofluid heat transfer and entropy generation in a double lid driven L-shaped cavity

Mixed convection has been one of the most interesting subjects of study in the area of heat transfer for many years. The entropy generation due to MHD mixed convection heat transfer in L-shaped enclosure being filled with Cu-water nanofluid and having an internal heating generation is explored in this investigation by the finite volume technique. Lid-motion is presented by both right and top parts of walls to induce forced convection and the cavity is under an inclined uniform magnetic field along the positive horizontal direction. The statistics concentrated specifically on the impacts of several key parameters like as the aspect ratio of the enclosure, Hartmann number, nanoparticle volume fraction, and heat source length/location on the heat transfer inside the L-shaped enclosure. Outcomes have been manifested in terms of isotherm lines, streamlines, local and average Nusselt numbers. The obtained results show that addition of nanoparticles into pure fluid leads to increase of heat transfer. The maximum value of local Nusselt pertaining to the heat source occurs when L = 0.1. Impacts of heat source size and location, internal heat generation absorption, angle of magnetic field on heat transfer and entropy generation are completely analyzed and discussed. The best configuration and values of important parameters are also presented using thermal performance criteria.

MHD and Viscous Dissipation Effects in Marangoni Mixed Flow of a Nanofluid over an Inclined Plate in the Presence of Ohmic Heating

The problem of Marangoni mixed convection in the presence of an inclined magnetic field with uniform strength in a nanofluid (formed by the dispersion of two metallic nanoparticles, i.e., Copper (Cu), and alumina (Al₂O₃) in water) is addressed numerically. The effects of viscous dissipation and Ohmic heating are also considered. The original set of governing partial differential equations is reduced to a set of non-linear coupled ordinary differential equations employing the similarity transformation technique. The simplified equations are numerically solved through MATLAB ‘bvp4c’ algorithm. The results are presented in terms of graphs for several parameters. It is found that enhancing the stratification parameter leads to a decrease in the fluid temperature, and an increase in the aligned magnetic field angle reduces the flow velocity. Moreover, mixed convection tends to enhance both the Nusselt and Sherwood numbers. If the angle of inclination is made higher, the fluid velocity is reduced and the thickness of the thermal and concentration boundary layer grows.

Effect of Two Baffles on MHD Natural Convection in U-Shape Superposed by Solid Nanoparticle having Different Shapes

In this paper, numerical Galerkin Finite Element Method (GFEM) applies for natural convection heat transfer of U-shaped cavity filled by Fe3O4-water nanofluid under the magnetic field and including two baffles. The above boundaries of the cavity are at low temperatures and bottom boundary is in a variable function temperature. It is assumed that two baffles in the cavity make vortexes to enhance heat transfers. The dimensionless governing equations including velocity, pressure, and temperature formulation are solved by the Galerkin finite element method. The results are discussed based on the governing parameters such as a nanoparticle volume fraction, Hartmann and Rayleigh numbers, magnetic field angle and nanoparticles shapes. As a main result, increasing both Aspect Ratio (AR) and Ra numbers enhanced heat transfer process and improved the average Nusselt numbers, while increasing the Hartmann number decreased the Nusselt number. Furthermore, it concluded that AR=0.4 had the maximum ψ and Nusselt numbers among the other examined aspect rations. Also, platelet, cylindrical, brick and spherical shapes had the maximum Nusselt numbers in sequence.

Topological properties of Josephson current between two s- and p-wave superconducting nanowires with Majorana fermions

Josephson current between two one-dimensional nanowires with proximity induced either s-wave or p-wave pairing and separated by a narrow dielectric barrier is calculated in the presence of Rashba spin-orbit interaction, in-plane and normal Zeeman magnetic fields. We show that Andreev retro-tunneling is realized by means of two channels. The main contribution to the Josephson current in junction of s- or p-wave superconductors is shown to give Andreev scattering in a conventional particle-hole channel, when an electron-like quasiparticle reflects to a hole-like quasiparticle with opposite spin yielding a current which depends only on the order parameters’ phase differences φ and oscillates with fractional 4π period. Nevertheless Andreev bound state energy in second anomalous particle-hole channel, corresponding to the reflection of an incident electron-like quasiparticle to a hole-like quasiparticle with the same spin orientation, survives only in the presence of the in-plane magnetic field, and oscillates with 4π period not only with φ but also with orientational angle of the in-plane magnetic field θ resulting in a magneto-Josephson effect. In the presence of Rashba spin-orbit coupling (SOC) and normal-to-plane magnetic field h, a forbidden gap is shown to open in the dependence of Andreev bound state energies on the phases φ and θ at several values of SOC strength and magnetic field, where Josephson current seems to vanish. The magnetic fields destroy also the particle-hole symmetry of the mid-gap states around Fermi level.

Hydromagnetic Dissipative and Radiative Graphene Maxwell Nanofluid Flow Past a Stretched Sheet-Numerical and Statistical Analysis

The key objective of this analysis is to examine the flow of hydromagnetic dissipative and radiative graphene Maxwell nanofluid over a linearly stretched sheet considering momentum and thermal slip conditions. The appropriate similarity variables are chosen to transform highly nonlinear partial differential equations (PDE) of mathematical model in the form of nonlinear ordinary differential equations (ODE). Further, these transformed equations are numerically solved by making use of Runge-Kutta-Fehlberg algorithm along with the shooting scheme. The significance of pertinent physical parameters on the flow of graphene Maxwell nanofluid velocity and temperature are enumerated via different graphs whereas skin friction coefficients and Nusselt numbers are illustrated in numeric data form and are reported in different tables. In addition, a statistical approach is used for multiple quadratic regression analysis on the numerical figures of wall velocity gradient and local Nusselt number to demonstrate the relationship amongst heat transfer rate and physical parameters. Our results reveal that the magnetic field, unsteadiness, inclination angle of magnetic field and porosity parameters boost the graphene Maxwell nanofluid velocity while Maxwell parameter has a reversal impact on it. Finally, we have compared our numerical results with those of earlier published articles under the restricted conditions to validate our solution. The comparison of results shows an excellent conformity among the results.

Spin Wave Resonance in the [(Co0.88Fe0.12)/Cu]N Synthetic Antiferromagnet

The [(Co0.88Fe0.12)/Cu]N synthetic antiferromagnet has been investigated by the spin wave resonance method over the entire range of angles of an external dc magnetic field to the film surface normal. The investigations have shown that the superlattice under study consists of two exchange-coupled magnetic subsystems, each manifested in the recorded spectra as a series of spin-wave modes. The dependence of the linear region of propagation of a standing spin-wave mode on the sample orientation in an external magnetic field has been established.

Heat transfer investigation of the fourth-grade non-Newtonian MHD fluid flow in a plane duct considering the viscous dissipation, joule heating and forced convection on the walls

The present study aims to investigate the heat transfer of the fourth-grade non-Newtonian MHD fluid flow in a plane duct analytically. The applied angular magnetic field is exerted on the channel walls and fluid flow. The effects of the viscous dissipation and joule heating, as well as forced convection heat transfer boundary conditions on the duct walls, are considered. The governing equations including momentum and energy are transformed into dimensionless forms; afterward, solved using the analytical method. As a novelty, the full energy equation is solved using the least squared method and the results are validated by the numerical 4th order Runge–Kutta (RK4) method. The results revealed since the Hartmann number increases, the bulk temperature inside the duct reduces about 20%, and the absolute value of the heat transfer rate on the duct wall decreases by about 40%. Besides, it was observed as the magnetic field angle reduces, the dimensionless temperature and absolute value of the temperature gradient decrease between 30 and 40%. When the Eckert number and Prandtl number decrease, the dimensionless temperature distribution becomes flattened; likewise, the heat transfer rate is reducing on the duct wall more than tripled. The increase of Biot number leads to a reduction of the dimensionless temperature inside the channel about three-time; however, the heat transfer rate increases first and then declines.

Angle Dependence of the Magnetic Phase Diagram in Cubic Chiral Antiferromagnet EuPtSi

The magnetic-field-induced A-phase for H ∥ [111] in cubic chiral antiferromagnet EuPtSi has been recently identified as a skyrmion lattice phase. We examined precise magnetic-field angle dependence...