Ferrimagnetic–ferromagnetic phase transition in Mn4N films favored by non-magnetic In doping

The ferrimagnet Mn4N forms a family of compounds useful in spintronics. In a compound comprising non-magnetic and magnetic elements, one basically expects the compound to become ferromagnetic when the proportion of the magnetic element increases. Conversely, one does not expect ferromagnetism when the proportion of the non-magnetic element increases. Surprisingly, Mn4N becomes ferromagnetic at room temperature when the Mn content is decreased by the addition of In atoms, a non-magnetic element. X-ray magnetic circular dichroism measurement reveals that the magnetic moment of Mn atoms at face-centered sites, Mn(II), reverses between x = 0.15 and 0.27 and aligns parallel to that of Mn atoms at corner sites, Mn(I), at x = 0.27 and 0.41. The sign of the anomalous Hall resistivity also changes between x = 0.15 and 0.27 in accordance with the reversal of the magnetic moment of the Mn(II) atoms. These results are interpreted from first-principles calculation that the magnetic moment of Mn(II) sites which are the nearest neighbors to the In atom align to that of Mn(I) sites.

MAGNETIC LEVITATION AS ENERGY HARVESTER

Magnetic levitation as energy harvester has been widely studied since past few years. It can be used to implement a low-cost and maintenance-free energy harvester. For self-powering a broad range of technologies for long periods of time, levitation-based harvesting systems able to operate autonomously. In this paper, a theoretical study is presented of a harvester conguration that utilizes the motion of a levitated hard-magnetic element to generate electrical power. The levitation used minimizes the loss caused due to wear and tear of mechanical part thus increasing the life of the system.

MECHATRONIC DEVICE FOR TWO-STAGE CLAMPING OF CYLINDRICAL OBJECTS IN MACHINE TOOL SPINDLES

The design of an electromechanical device for fixing cylindrical objects in the spindle units of technological equipment is presented. The new two-stage concept of the clamping process with a separated first stage is developed. The design of the presented mechanism provides advanced capabilities for control and regulation of its operating characteristics. The control system with the possibility of carrying out the first stage of clamping in automatic mode and without connecting to the upper-level control system in a technological machine is proposed. The involvement of electrical devices for the conversion and transmission of energy instead of their mechanical analogues is used as one of the promising ways to increase the performance efficiency of machine units. It helps to simplify and expand control capabilities, as well as reduce energy losses during intermediate transformations. The absence of mechanical energy converters in the proposed structure helps to reduce energy losses on intermediate transformations. The simplicity of the design expands the possibilities of integration of the proposed clamping mechanism into the structure of both new and existing technological machines in order to modernize it. This allows to achieve technical results, such as an expansion of the metalworking machines functionality, increase the level of automation of the clamping process and the accuracy of clamping objects in spindle units. The task is achieved by equipping the jaw of the clamping chuck with a special mechanism for identifying the presence of the object for clamping. For this goal, the clamping jaw is equipped with a probe that is capable of simultaneous force interaction with the object and the plunger. The plunger is rigidly attached to the magnetic element whose magnetic field has the possibility to interact with the magnetic field sensor. The sensor transmits its electrical signals to the control system of the device. The research results are aimed at meeting the requirements for effective control of clamping mechanisms with the possibility of automatic operation according to a preset algorithm for maintenance of optimal characteristics of a clamping process and a wide range of optional settings.

Solar cycle-related variation in solar differential rotation and meridional flow in solar cycle 24

We studied temporal variation of the differential rotation and poleward meridional circulation during solar cycle 24 using the magnetic element feature tracking technique. We used line-of-sight magnetograms obtained using the helioseismic and magnetic imager aboard the Solar Dynamics Observatory from May 01, 2010 to March 26, 2020 (for almost the entire period of solar cycle 24, Carrington rotation from 2096 to 2229) and tracked the magnetic element features every 1 h. We also estimated the differential rotation and poleward meridional flow velocity profiles. The observed profiles are consistent with those of previous studies on different cycles. Typical properties resulting from torsional oscillations can also be observed from solar cycle 24. The amplitude of the variation was approximately ±10 m s$$^{-1}$$ - 1 . Interestingly, we found that the average meridional flow observed in solar cycle 24 is faster than that observed in solar cycle 23. In particular, during the declining phase of the cycle, the meridional flow of the middle latitude is accelerated from 10 to 17 m s$$^{-1}$$ - 1 , which is almost half of the meridional flow itself. The faster meridional flow in solar cycle 24 might be the result of the weakest cycle during the last 100 years.

Solar Cycle Related Variation in Solar Differential Rotation and Meridional Flow in Solar Cycle 24

We studied temporal variation of the differential rotation and poleward meridional circulation during solar cycle 24 using the magnetic element feature tracking technique. We used line-of-sight magnetograms obtained using the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory from May 01, 2010 to March 26, 2020 (for almost the entire period of solar cycle 24, Carrington Rotation from 2096 to 2229) and tracked the magnetic element features every 1 hour. We also estimated the differential rotation and poleward meridional flow velocity profiles. The observed profiles are consistent with those of previous studies on different cycles. Typical properties resulting from torsional oscillations can also be observed from solar cycle 24. The amplitude of the variation was approximately ±10 m s−1. Interestingly, we found that the average meridional flow observed in solar cycle 24 is faster than that observed in solar cycle 23. In particular, during the declining phase of the cycle, the meridional flow of the middle latitude is accelerated from 10 to 17 m s−1, which is almost half of the meridional flow itself. The faster meridional flow in solar cycle 24 might be the result of the weakest cycle during the last 100 years.

Single Magnetic Element-Based High Step-Up Converter for Energy Storage and Photovoltaic System with Reduced Device Count

The multiport DC-DC power converter is a prominent area of research in power electronics due to its highly dense design, reduced device count, and high energy efficiency. In this paper, a nonisolated single magnetic element-based high step-up three-port converter for an energy storage system is presented. The proposed converter has two input ports and one output port. The coupled inductor with switched capacitor is used to achieve high voltage gain. The key features of the proposed converter are high conversion gain, low voltage stress, zero voltage switching (ZVS), and zero current switching (ZCS). The detailed theoretical analysis and operation of the converter are elaborated. The energy efficiency of the proposed converter is calculated and compared with the other counterparts. Ansys Maxwell is used for the coupled inductor finite element modeling. To verify the applicability and functionality of proposed converter, a 100 W converter with two inputs ( 48 V and 96 V ) and one output 360 V at 100 kHz is tested in the laboratory.

Solar Cycle Related Variation in Solar Differential Rotation and Meridional Flow in Cycle 24

We studied temporal variation of the differential rotation and poleward meridional circulation during solar cycle 24 using the magnetic element feature tracking technique. We used line-of-sight magnetograms obtained using the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory from May 01, 2010 to March 26, 2020 (for almost the entire period of solar cycle 24, Carrington Rotation from 2096 to 2229) and tracked the magnetic element features every 1 hour. We also estimated the differential rotation and poleward meridional flow velocity profiles. The observed profiles are consistent with those of previous studies on different cycles. Typical properties resulting from torsional oscillations can also be observed from solar cycle 24. The amplitude of the variation was approximately $\pm$10 m s$^{-1}$. Interestingly, we found that the average meridional flow observed in solar cycle 24 is faster than that observed in solar cycle 23. In particular, during the declining phase of the cycle, the meridional flow of the middle latitude is accelerated from 10 to 17 m s$^{-1}$, which is almost half of the meridional flow itself. The faster meridional flow in solar cycle 24 might be the result of the weakest cycle during the last 100 years.

Current vortices and magnetic fields driven by moving polar twin boundaries in ferroelastic materials

Ferroelastic twin boundaries often have properties that do not exist in bulk, such as superconductivity, polarity etc. Designing and optimizing domain walls can hence functionalize ferroelastic materials. Using atomistic simulations, we report that moving domain walls have magnetic properties even when there is no magnetic element in the material. The origin of a robust magnetic signal lies in polar vortex structures induced by moving domain walls, e.g., near the tips of needle domains and near domain wall kinks. These vortices generate displacement currents, which are the origin of magnetic moments perpendicular to the vortex plane. This phenomenon is universal for ionic crystals and holds for all ferroelastic domain boundaries containing dipolar moments. The magnetic moment depends on the speed of the domain boundary, which can reach the speed of sound under strong mechanical forcing. We estimate that the magnetic moment can reach several tens of Bohr magnetons for a collective thin film of 1000 lattice planes and movements of the vortex by the speed of sound. The predicted magnetic fields in thin slabs are much larger than those observed experimentally in SrTiO3/LaAlO3 heterostructures, which may be due to weak (accidental) forcing and slow changes of the domain patterns during their experiments. The dynamical multiferroic properties of ferroelastic domain walls may have the potential to be used to construct localized magnetic memory devices in future.